shoulder mri

99

INTRODUCTION

The shoulder is a joint capable of great freedom andmotion. It is therefore both inherently unstable and sub-ject to injury. Shoulder pain is thus a common clinicalproblem. It has a number of different etiologies, includ-ing subacromial and other forms of impingement leadingto rotator cuff tendon failure, and various forms ofglenohumeral joint instability. These diseases may bemisdiagnosed clinically or dismissed with nonspecificdiagnoses, including bursitis or synovitis. In the absenceof a precise diagnosis, treatment may fail to relieve thesymptoms, resulting in chronic limitation of motion,atrophy, and persistent pain.

MRI is accepted as the imaging modality of choice inpatients with shoulder pain. It is a useful and accuratetechnique in noninvasively diagnosing many shoulderdisorders, particularly those due to rotator cuff diseaseand shoulder instability. This chapter will review currentexperience with this modality and discuss relevant tech-nical, anatomic, and pathologic issues.

TECHNICAL FACTORS

Local Coils

Local radiofrequency coils are critical to MRI of joints,1

including the shoulder, as they provide greater diag-nostic capability through an increase in signal-to-noiseratio (SNR). Since noise is inherent in the tissue being

imaged, it is important that a radiofrequency coiladequately covers the area of interest, but covers as littleunwanted tissue as possible. In general, larger coils havelower SNR; therefore, it is important to use the smallestcoil feasible to adequately encompass the area ofinterest. Linear coils which consist of a single loop arelimited as the homogeneity of the image and SNRdegrade sharply away from the center of the loop,producing suboptimal image quality for diagnosis ofdeeper structures such as the labrum. Helmholtz coils,consisting of two parallel loops with the anatomy ofinterest sandwiched between them, provide betterhomogeneity than a linear loop coil. The SNR perform-ance is somewhat less than at the center of a loop.Flexible coils are used commonly by some manufac-turers. They consist of one or more linear loops thatwrap (once) around the area of interest. While flexiblecoils offer good patient comfort and reasonablediagnostic capability, their performance is easily sur-passed by quadrature or array coils designed specificallyfor imaging the shoulder. Quadrature (circularlypolarized, CP) coils provide significant improvementsin image quality over linear loop coils, with good SNRand homogeneity available over the entire joint. Someflexible coils may have a quadrature design. Flexiblequadrature coils have the “flexible” positioning optionsof flex coils, but with superior SNR performance.

A multicoil (also known as phased) array consists oftwo or more resonating loops. The output signal of eachloop is fed into an independent channel of the MRIsystem. Since each channel is independent from theothers, the coil receivers do not share noise as long as

C H A P T E R 99SHOULDER

Michael B. Zlatkin

INTRODUCTION 3204

TECHNICAL FACTORS 3204Local Coils 3204Pulse Sequences and

Parameters 3205MRI Arthrography 3206Imaging Protocols 3207General Shoulder Anatomy 3207MRI Anatomy 3214

ROTATOR CUFF DISEASE 3222Pathophysiology 3222

Classification, Location, and Incidenceof Rotator Cuff Tears 3226

Magnetic Resonance Imaging 3227

SHOULDER INSTABILITY 3245General Features 3245Anterior Instability 3246Posterior Instability 3250

POSTOPERATIVE SHOULDER 3259Impingement and Rotator Cuff

Disease 3260Deltoid Detachment 3262

Biceps Tendon Rupture 3262Shoulder Instability 3262

OTHER DISORDERS 3266Occult Fractures 3266Muscle Injuries 3267Inflammatory and Degenerative

Joint Processes 3268Osteochondral Lesions 3269Avascular Necrosis 3270Quadrilateral Space Syndrome 3270Parsonage-Turner Syndrome 3271

3204

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they remain electrically isolated from each other.Although MRI scanners can handle as many as 8 or 16multicoil array channels, currently most shoulder arraycoils are four-channel arrays (Fig. 99-1). Shouldermulticoil arrays will permit imaging with highresolution, small fields of view, and thin sections.

Pulse Sequences and Parameters

Conventional spin-echo sequences have for the mostpart been replaced in MRI by fast spin-echo imagingsequences. Short repetition time (TR)/time to echo (TE)images are still, however, helpful to demonstrateanatomic details and are most often used in MRarthrography.

The tissue contrast is similar in fast spin-echo imagingsequences to that seen with conventional spin echo;however, fat is more intense on T2-weighted fast spin-echo images, and therefore differentiating fat from fluidsignal can sometimes be difficult. Blurring of anatomicstructures is another problem, especially on short TEsequences. Comparative studies have established theefficacy of fast spin-echo techniques.2-6 Since marrow fatis brighter, marrow edema can be obscured and fluid intears or in effusions may be more difficult to identify.Thus most commonly, fat-suppression techniques areadded.

Gradient-echo sequences2,5,7-9 may be applied inimaging the shoulder. These techniques can be used forkinematic imaging10-15 and are also used to evaluate theglenoid labrum. Problems with the gradient-echotechnique include the vacuum phenomenon,16 whichmay simulate loose bodies or calcification, and increasedmagnetic-susceptibility artifact.

Fat suppression is useful in shoulder MRI as it canincrease the conspicuity of an abnormality. This effectis most prominent on T2-weighted sequences. Detec-tion of abnormal enhancement after contrast injectionis improved on T1-weighted images by using fat sup-

pression. TR and TE can also be reduced on T2-weightedfast spin-echo sequences without loss of tissue contrast,and imaging sequences with TEs in the 35 to 45 ms rangeare often used with fat saturation in place of imag-ing sequences with longer TEs and poorer SNR. Fatsuppression also reduces phase-encoding and chemicalshift artifacts. The two most common types of fat sup-pression are short tau inversion recovery (STIR) imagingand fat saturation. STIR images exhibit combined T1 andT2 contrast, which enhance sensitivity but diminishspecificity. Fat saturation uses a radiofrequency pre-saturation pulse applied at the resonant frequency oflipid protons, followed by a gradient pulse designed tospoil any residual signal intensity of fat. This technique isbetter with high field-strength systems and a highlyuniform magnetic field.6,17 Methods such as STIR and fat-saturation T2 can improve visualization of rotator cufftendon injuries (Fig. 99-2) and hyaline cartilage lesions,and are also used to evaluate marrow abnormalities, andinflammatory and post-traumatic processes. They mayalso be useful to evaluate labral tears.

Performance of high-resolution imaging using largematrices has recently become available, with systemscapable of performing 512 × 512 matrices, or usingparallel imaging, 3-T magnets, and appropriate coils evenhigher matrices may be employed (Fig. 99-3). Thesetechniques may improve visualization of subtle abnor-malities involving the labrum and rotator cuff. Smallerfields of view18 are also helpful in the evaluation of theshoulder. Large matrix and/or small field of view imagingis made possible by higher field strength, improvementsin scanner hardware, better local coils, or such standardfactors as increased excitations and longer repetitiontime. A narrow receiver bandwidth also improves SNR.

The slice thickness is also an important determinantof spatial resolution. Slice thicknesses of 2 mm on two-dimensional (2D) spin- and gradient-echo sequencesand thicknesses of 1 mm or less on 3D Fourier transform(FT) images are available on most scanners for routineusage. These are also very useful for evaluating such

C H A P T E R 99 ■ SHOULDER 3205

A B

F I G U R E 99-1

Technique. A, Four-channel array coil consisting of four linear coils arranged in a strip. The arrows represent theB1 field of each coil in the array. B, Four-channel array shoulder coil positioned on a normal volunteer. Patients areimaged in a supine position, with their arm by the side in the neutral rotation. (Courtesy of Tom Schubert, MRIDevices Corporation, Waukesha, WI.)

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structures as the glenoid labrum and subtle injuries ofarticular cartilage. Contiguous thin slices ensure that therelevant anatomy is adequately covered and also reducepartial volume averaging.

MRI Arthrography

In the absence of a native effusion MRI can beperformed after the injection of saline or a gadopentatedimeglumine/saline mixture for MR arthrography.19-35 Asaline/gadopentate dimeglumine mixture (1.0 mL ofgadopentate dimeglumine/200 mL of saline) is injected.This can be achieved by diluting 0.1 mL of gadolinium in20 mL of saline. The amount depends on the capacity ofthe joint,but is typically 12 to 15 mL,which is somewhatgreater than for conventional arthrography. The patientis then taken to the MRI scanner and the appropriateimage sequences are obtained. As mentioned earlier, fat-saturation techniques are often utilized in conjunction toincrease the conspicuity of the contrast.32,34,36 Intra-articular gadolinium distends the joint and potentiallycan more directly identify abnormalities (Fig. 99-4). Inthe shoulder, it is utilized to assess the rotator cuffundersurface and to improve assessment of torn tendonedges in complete cuff tears. It is very helpful in eval-uating the postoperative shoulder and in assessingpatients with glenohumeral instability and SLAP tears,when findings are uncertain, or when there is no nativeeffusion.1 Positioning patients in abduction and externalrotation (ABER)37-39 may help visualize posterior under-surface lesions in posterosuperior subglenoid impinge-ment and help to visualize labroligamentous abnor-malities in complex instability cases, including Bankartlesion variants. MR arthrography may help locate loosebodies but may not be as effective as CT air arthrographyfor this application.

Disadvantages of gadolinium injection are that itrequires an injection into the joint, making the study

semi-invasive. Fluoroscopy is required for injection andtherefore the total examination time is increased. Ourpatients are injected under C arm fluoroscopic guidance.In addition, imaging may be logistically difficult toperform if the scanner is remote from the fluoroscopicunit. Although no toxic effects are known, the intra-articular use of gadolinium21 has not yet been approvedby the Food and Drug Administration (FDA).

Indirect MR arthrography is achieved by injectionof paramagnetic MR contrast media intravenouslyinstead of as an intra-articular injection as in direct MRarthrography.40-43 In some cases, exercising the jointresults in considerable signal intensity increase within

3206 S E C T I O N VII ■ MUSCULOSKELETAL SYSTEM

A B

F I G U R E 99-2

Fat suppression. A, Conventional spin-echo T2-weighted image. B, T2-weighted fast spin-echo (FSE) image with fatsaturation. Fat saturation increases the conspicuity of the tendon disruption (arrows in A and B).

F I G U R E 99-3

Image of the shoulder obtained with a four-channel phased-array coil at3 T. Note the severe tendinosis and small undersurface anterodistal partialtear (arrow). (Courtesy of Larry Tannenbaum MD, Edison, NJ.)

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the joint cavity where fat-saturated MR sequences yieldarthrographic images.44 The method is less invasive thandirect MR arthrography and initial results claimcomparable sensitivities and specificities for rotator cuffand glenoid labrum pathology.45-47

Imaging Protocols

In shoulder imaging, patients are typically positionedsupine, with the arm at the side in a neutral rotation (seeFig. 99-1B).With the arm in external rotation the capsuleis generally taut; with the arm in internal rotation it mayappear more redundant. External rotation is generallyavoided except under special circumstances, as this isuncomfortable and may result in motion artifact. Thearm should not be placed on the chest or abdomen toavoid transmitted respiratory motion.

In the routine shoulder protocol an axial dual-echoproton-density and T2-weighted fast spin-echo pulsesequence is obtained first with fat saturation. Someexaminers perform this sequence as an intermediate-echo fast spin-echo sequence (TE 35-45 ms) with fatsaturation.Especially in patients with shoulder instabilitythis is followed by a sliced interleaved gradient-echo(MPGR) T2* gradient-echo sequence, also in the axialplane. The oblique coronal images are performed nextand are oriented from the axial images perpendicular tothe glenoid margin. Others orient these parallel to thecourse of the supraspinatus tendon on axial images. Thissequence best evaluates the rotator cuff. A fast spin-echoproton-density–weighted sequence is carried out,without fat suppression, followed by a T2-weighted fastspin-echo sequence with fat saturation. Sagittal oblique

images can be obtained with an intermediate-echo fastspin-echo sequence with fat saturation.

MRI arthrography is performed in selected cases asdiscussed earlier (see Fig. 99-4). Twelve to 15 mL of con-trast is injected. T1-weighted images with fat saturationin the axial, coronal oblique, and sagittal oblique planesare obtained. This is then followed by a T2-weighted fastspin-echo sequence, typically in the axial and coronaloblique planes.

The field of view is 12 to 14 cm and the slice thick-ness is 3 to 4 mm. The matrix size is 256 × 192 or256 × 256 for the T1 and gradient-echo sequences. Forfast spin-echo imaging, a 384 × 256 matrix is employedwith an echo train of three to four for the proton-density–weighted images and seven to eight for theT2-weighted images.

General Shoulder Anatomy

The shoulder enjoys a greater range of motion than anyother joint in the body. In fact it is not a single joint, butthe synergistic action of four separate articulations:glenohumeral, acromioclavicular, sternoclavicular, andscapulothoracic joints.

Glenohumeral Joint

The glenohumeral joint is a multiaxial ball and socketjoint lying between the roughly hemispheric humeralhead and the shallow glenoid fossa of the scapula.48 Theglenoid fossa is essentially a pear-shaped cavity withdimensions approximately a quarter the size of thehumeral head.49 The glenoid is covered by articular


SCT

MGHL

AL

A B

F I G U R E 99-4

MR arthrography. T1-weighted images with fat saturation obtained after intra-articular gadolinium injection (1/200dilution of gadolinium in saline). A, Coronal oblique image. Note the high signal obtained from gadolinium outliningthe cuff undersurface (arrow). B, Axial image shows the excellent delineation of the anterior labrum (AL), middleglenohumeral ligament (MGHL), and subscapularis tendon (SCT) when the joint is distended with contrast. A smallposterior labral tear is seen (arrow).

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cartilage that is thinner centrally. The humeral head isalso covered with articular cartilage which thinsslightly at the periphery to accentuate glenohumeraljoint congruity.50 This anatomy permits a wider range ofmotion than is possible at any other joint. The shoulderis capable of flexion-extension, abduction-adduction,circumduction, and medial and lateral rotation.48 Thisanatomy provides mobility,but renders the joint unstableand prone to subluxation and dislocation. This is due tothe small size of the glenoid fossa compared to thehumeral head and the relative laxity of the joint capsule.These movements and the associated inherent insta-bility of the glenohumeral joint may also be important inthe development of internal impingement in theoverhead throwing athlete.51

The proximal end of the humerus consists of the headand greater and lesser tuberosities. The humeral head isnormally retroverted approximately 30 degrees with thearm in the anatomic position. The articular surface isdirected superiorly,medially, and posteriorly with an axisangled 130 to 150 degrees relative to the humeral shaft.50

The anatomic neck of the humerus lies at the base of thearticular surface at the proximal end of the bone. Theneck is the site of attachment of the inferior aspect ofthe joint capsule. The greater tuberosity is located on thelateral aspect of the proximal humerus and is the site ofinsertion of the supraspinatus, infraspinatus, and teresminor tendons (Fig. 99-5). The supraspinatus tendon

inserts on the highest point of the greater tuberosity(Fig. 99-5). The infraspinatus and teres minor tendonslocalize, respectively, to the middle and lower thirds ofthe greater tuberosity and lie somewhat more posteriorlythan the supraspinatus tendon insertion. The lessertuberosity is situated on the anterior portion of theproximal humerus, medial to the greater tuberosity.The subscapularis tendon inserts here in a broad band(Fig. 99-5).

The intertubercular (bicipital) groove is locatedbetween the greater and lesser tuberosities. The trans-verse humeral ligament stretches between the twotuberosities, forming the roof of the intertuberculargroove. The tendon of the long head of the biceps brachiimuscle passes through here, surrounded by a synovialsheath (Fig. 99-6). The width of the groove can vary andif shallow this may predispose it to impingement. Belowthe greater and lessor tuberosities, the humerus tapers tothe surgical neck. The intertubercular groove at thislevel normally then becomes shallower, and its mediallip provides the insertion site for the latissimus dorsiand teres major tendons; its lateral lip provides the inser-tion site for the pectoralis major.50 The deltoid insertsalong the deltoid tuberosity, a smooth broad bonyprominence on the midportion of the diaphysis. Thecoracobrachialis also inserts at this level along the medialborder of the humerus. The long head of the tricepsmuscle attaches to the infraglenoid tubercle, which is a


F I G U R E 99-5

Rotator cuff muscles and tendons. Note the supraspinatus tendon insertsmore superiorly and anteriorly on the greater tuberosity, and theinfraspinatus and teres minor more posteriorly and inferiorly. Thesubscapularis is anterior and inserts broadly in a fanlike fashion on the lessertuberosity. ISM, infraspinatus muscle; IST, infraspinatus tendon; SSM,supraspinatus muscle; SST, supraspinatus tendon; SCM, subscapularismuscle; SCT, subscapularis tendon; TM, teres minor muscle; TMT, teresminor tendon. (Reproduced with permission from Zlatkin MB: MRI of theShoulder, 2nd ed. Philadelphia, Lippincott, Williams and Wilkins, 2003.)

F I G U R E 99-6

Coracoacromial arch and surrounding structures. Note the relationship ofthe supraspinatus tendon to the anterior acromion, acromioclavicular joint,and coracoacromial ligament. The long head of the biceps tendon is also animportant relation of this arch. ACJ, acromioclavicular ligament; ACR,acromion; BT, biceps tendon; CAL, coracoacromial ligament; SCTsubscapularis tendon; SST, supraspinatus tendon; TL, transverse humeralligament. Arrow, biceps tendon sheath. (Reproduced with permission fromZlatkin MB: MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott, Williamsand Wilkins, 2003.)

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triangular surface where the inferior glenoid rim joinsthe lateral scapular border.50

Hyaline articular cartilage lines the surfaces of thehumeral head. The cartilage on the humeral head isthickest at its center. The blood supply to the humeralhead is via the anterior humeral circumflex artery. Thereis a normal “sulcus” located posteriorly on the humeralhead.52 This represents an area of “bare bone” betweenthe insertion of the posterior capsule and overlyingsynovial membrane and the edge of the articular surfaceof the humeral head. The appearance of this sulcus oncross-sectional images has sometimes been confusedwith a Hill-Sachs lesion.

The glenoid fossa is situated on the superolateralaspect of the scapula (Figs. 99-7 and 99-8). The superiorportion of the fossa is narrow and the inferior portion isbroad. In man there is greater anterior tilt to the glenoidfossa and therefore greater anterior instability.53,54 Theglenoid fossa is lined by articular cartilage, thinner in thecenter. The glenoid labrum rims the glenoid cavity, andprovides inherent stability to the glenohumeral joint,restricting anterior and posterior excursion of thehumerus (Figs. 99-7 and 99-8).49 The labrum consists ofhyaline cartilage, fibrocartilage, and fibrous tissue.Fibrocartilage is present in the labrum only in a smalltransition zone at the attachment to the osseous glenoidrim. The blood supply of the labrum is mainly to theoutermost portion of the labrum. The inner portion iswithout vessels.

The glenoid labrum is variable in size and thickness.In young patients the labrum is closely attached at itsbase to the glenoid, blending with the fibrils of hyalinearticular cartilage. In later years especially the superior

portion of the labrum may rest free on the edge of theglenoid. This may arise as a result of pull by the superiorglenohumeral ligament and biceps tendon and may bedistinguished from a labral tear by its smooth borders. Inyoung athletes superior quadrant labral tears may resultfrom traction by these same two structures in overheadthrowing.55

The fibrous glenoid labrum deepens and enlarges theshallow glenoid fossa. The glenoid is also deepened bythe thin cartilaginous lining in the center of thisstructure. The labrum is also important as a site forligamentous attachment (see Fig. 99-7).56 It is believedthat the strong intertwining between the collagen fibersof the glenohumeral ligaments and the labrum is moreresistant to injury than the glenolabral junction/union.There appears to be a strong pathophysiologic relation-ship between the locations of labral lesions and the


F I G U R E 99-7

Cross-sectional diagram illustrating important structures and relations ofthe shoulder. ACR, acromion; AR, axillary recess; CL, clavicle; D, deltoidmuscle; SDB, subacromial-subdeltoid bursa; SSM, supraspinatus muscle;SST, supraspinatus tendon. (Reproduced with permission from Zlatkin MB:MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott, Williams and Wilkins,2003.) F I G U R E 99-8

Capsular mechanism and surrounding structures. The capsule andglenohumeral ligaments are seen. The superior labrum, superiorglenohumeral ligament, and biceps tendon converge superiorly. Theconvergence of the superior labrum and biceps tendon superiorly is knownas the biceps labral anchor. There is an opening into the subscapularis bursabetween the middle and superior glenohumeral ligaments. The inferiorglenohumeral ligament merges with the labrum inferiorly. It is divided intoan anterior band, axillary pouch, and posterior band. 1, subscapularismuscle; 2, anterior capsule; 3, superior glenohumeral ligament; 4, middleglenohumeral ligament; 5, inferior glenohumeral ligament; AB, anteriorband; AP, axillary pouch; PB, posterior band; 6, biceps tendon, long head;7, posterior capsule; 8, posterior rotator cuff; L, glenoid labrum;G, glenoid. (Reproduced with permission from Zlatkin MB, Bjorkengren AG,Gylys-Morin V, et al: Cross-sectional imaging of the capsular mechanism of theglenohumeral joint. Am J Roentgenol 150:151-158, 1988.)

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attachment sites of the glenohumeral ligaments andproximal biceps tendon (see Fig. 99-8).57,58 The inferiorportion of the labral-ligamentous complex is moreimportant than the superior portion in stabilizing theglenohumeral joint. It is this portion of the labrum that ismore commonly injured in patients with anteriorglenohumeral instability. Nonethelesss, the superiorlabrum does play some role in the stability of theglenohumeral joint where it functions in conjunctionwith the biceps tendon, through the biceps labral com-plex (see Fig. 99-8). The superior and anterior superiorportions of the labrum are the more variable in theirattachment to the glenoid, while the more inferiorportion of the labrum is typically fixed.

A loose, redundant fibrous capsule envelops the joint.It is lined by a synovial membrane, and has a surface areaapproximately twice that of the humeral head (seeFigs. 99-7 and 99-8).50 It encompasses all the intra-capsular soft-tissue structures, including the bicepstendon, glenohumeral ligaments, labrum, and synovialrecesses. In the bursal recesses this membrane may beredundant. Superiorly, the capsule encroaches on theroot of the coracoid process and inserts in the supra-glenoid region. Laterally the capsule inserts into theanatomic neck of the humerus and inferiorly intothe periosteum of the humeral shaft.With the arm at theside the lower part of the capsule is lax, formingthe axillary recess (see Figs. 99-7 and 99-8). Posteriorlyand inferiorly, the capsule is continuous with the cap-sular border of the labrum and the adjacent bone.Medially, the anterior capsular insertion may be variable59

based on its relationship to the glenoid labrum. It mayinsert directly into the labrum.60 In a smaller percentageof cases it may insert progressively more medially alongthe scapular neck, which has been considered to be lessstable. Investigation with MRI and MR arthography hascalled into question the correlation between the type ofcapsular insertion and glenohumeral instability.61

The fibrous capsule is strengthened in several areas.The coracohumeral ligament is a strong fibrous bandextending from the coracoid process over the humerusto attach to the greater tuberosity. It has a more impor-tant function in shoulder stability than previouslythought.62-65 It also supports the long head of the bicepstendon in the intertubercular groove, and it is disruptionof this structure rather than the subscapularis tendon, orits extension into the transverse humeral ligament, thatappears to be the main cause of intra-articular subluxa-tion of the biceps tendon. Anteriorly, the capsule maythicken to form the superior (SGHL), middle (MGHL),and inferior glenohumeral ligaments (IGHL) (Figs. 99-8and 99-9).66-68 These ligaments reinforce the anteriorportion of the capsule and act as a check to externalrotation of the humeral head.66,69 They extend fromadjacent to the lesser tuberosity to the anterior border ofthe glenoid fossa.

The superior glenohumeral ligament, together withthe coracohumeral ligament, stabilizes the shoulder jointwhen the arm is in the adducted dependent position.The ligament consists of two proximal attachments; oneto the superoanterior aspect of the labrum conjoinedwith the biceps tendon, and the other to the base of the

coracoid process (Figs. 99-8, 99-9, and 99-10). Thisligament projects in a lateral fashion to insert along theanterior aspect of the anatomic neck of the humerus,superior and medial to the lesser tuberosity.49,52

The middle and inferior glenohumeral ligamentsblend with the labrum at a level lower than that of thesuperior ligament (see Figs. 99-8, 99-9, and 99-10). Theseligaments and the recesses between them are quitevariable.66,69 The greatest variation is in relation to themiddle glenohumeral ligament. This ligament providesstabilization to the glenohumeral joint when theshoulder is abducted 45 degrees. It originates from justbeneath the superior glenohumeral ligament alongthe anterior border of the glenoid to the junctionsof the middle and inferior third of the glenoid rim. Itblends with the anteroinferior aspect of the capsule,and inserts along the anterior aspect of the surgicalneck of the humerus, anterior and inferior to the lessertuberosity.49,52

The inferior glenohumeral ligament has a complexconfiguration (see Figs. 99-8, 99-9, and 99-10).70,71 It maybe identified as a distinct structure or as just a diffusethickening of the capsule. It is the thickest portion of thecapsule. It consists of three portions: anterior band,posterior band, and axillary pouch/recess of the capsule.It stabilizes the glenohumeral joint when the arm isabducted to approximately 90 degrees (see Figs. 99-8,99-9, and 99-10).22,72 The ligament has a triangular con-figuration with its origin from the anteroinferior andposterior margin of the glenoid rim below its epiphysealline and its origin is inseparable from the base of thelabrum. The inferior glenohumeral ligament inserts alongthe inferior aspect of the surgical neck of the humerus.

The capsule is reinforced by the tendons of therotator cuff muscles: the supraspinatus, infraspinatus,teres minor, and subscapularis muscles. These tendonsall blend with the fibrous capsule to form the musculo-tendinous cuff (see Fig. 99-5). The primary function ofthe supraspinatus muscle and tendon complex is toabduct the humerus, but it also has a role in humeralrotation, and also functions as a counterbalance to thedeltoid by depressing the humeral head.50 The inner-vation of the supraspinatus muscle is by the supra-scapular nerve (C5 and C6 roots), which passes throughthe suprascapular notch. The suprapinatus tendon mayconsist of two distinct portions. The ventral portionoriginates from the anterior supraspinatus fossa insertinganteriorly onto the greater tuberosity. This ventralportion of the supraspinatus tendon may additionallyhave a site of insertion onto the lesser tuberosity andthere may function as an internal rotator of the arm. Thesecond portion of the supraspinatus is located moreposteriorly, in a “straplike” configuration. It has severalsmall tendon slips which coalesce into a broad fibrousattachment inserting more posteriorly onto the greatertuberosity. This portion acts primarily as a shoulderabductor.73 In addition, medially originating fibers fromboth muscle portions merge in a bipennate fashionto form a strong tendon eccentrically located withinthe muscle.

The main function of the infraspinatus muscle-tendonunit is external rotation. It also functions to depress the


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SGHL

BT AL

PL

MGHL

SCT

AL

PL

SCB

SGHL

BT

BLC AL

PL

IGHL

IGHL

L

L

MGHL

SCT

AL

AC

SCB

A

B

C

D

E

F

F I G U R E 99-9

Cross-sectional anatomy of the glenohumeral ligaments and surrounding structures (axial plane). MR images (TR/TE800/20 ms) with fat saturation obtained after intra-articular gadolinium injection, and corresponding cadaver sections.A and B, Superior attachments of the superior glenohumeral ligament are seen with the biceps tendon into thesuperior glenoid, with the superior labrum, and more anteriorly along the coracoid. The confluence of the bicepstendon long head and superior labrum forming the biceps-labral anchor is also seen. AL, anterior superior labrum;BLC, biceps-labral complex; BT, biceps tendon long head; PL, posterior superior labrum; SGHL, superior gleno-humeral ligament. C and D, Midglenoid level shows the relationship of the anterior labrum (AL) to the middleglenohumeral ligament (MGHL), anterior capsule (AC), and subscapularis tendon (SCT). The subscapularis bursa iscontinuous with the joint and extends anterior to the subscapularis tendon (SCB). E and F, Anterior inferior glenoidlevel. Here the anterior band of the inferior glenohumeral ligament (IGHL) and subjacent capsule is thick and formsa complex with the labrum (L), which is usually also round and thick at this level.

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humeral head, and as a static stabilizer of the gleno-humeral joint, resists posterior subluxation.50 Theinfraspinatus muscle is innervated by the distal fibers ofthe suprascapular nerve. The infraspinatus tendon isposterior to the supraspinatus tendon and inserts on themiddle facet of the greater tuberosity, inferior andposterior to the supraspinatus tendon.

The teres minor is posteroinferior to the infraspinatus(see Fig. 99-5). It is a powerful external rotator of thehumerus. It also helps resist subluxation of the humeralhead.50 The teres minor muscle is innervated bybranches of the axillary nerve. It also forms part of theborder of the quadrilateral space as well as the trian-gular space.

The subscapularis is the largest and most powerfulmuscle of the rotator cuff with a broad-based belly thatoriginates from the anterior scapula (see Fig. 99-5). It hasfour to six strong tendon slips that arise medially deepwithin the muscle. These slips converge to form a maintendon that inserts along the superior aspect of thelesser tuberosity.74 Additional tendon fibers from thesubscapularis merge with the transverse humeralligament and extend across the floor of the bicipitalgroove, fusing with those of the supraspinatus tendoninto a sheath that encompasses the biceps tendon.75 Thesubscapularis muscle is supplied by the upper and lowersubscapular nerve.50 In addition to the subscapularis’primary role in active internal rotation, it also functionsin adduction, depression, flexion, and extension. Thesubscapularis tendon also reinforces the anterior jointcapsule. It is separated from the rest of the rotator cufftendons by the rotator cuff interval.

The rotator cuff tendons fuse along their distalattachments to the greater and lesser tuberosities toprovide a continuous water-tight unit.76 Prior to their

fusion, the anatomic space between the supraspinatusand subscapularis along the anterosuperior aspect ofthe shoulder is the rotator interval (Fig. 99-11). It is acomplex region and can be conceptualized in layers.68,77,78

The outermost layer consists of fibrofatty tissue andbeneath this is the coracohumeral ligament, the rotatorinterval capsule, and then the superior glenohumeralligament. The coracohumeral ligament courses fromthe coracoid process into the interval, fusing with theinterval capsule. This capsule/ligament complex extendssuperiorly merging and fusing with the anteriormargin and superficial/deep fascial fibers of the supra-spinatus anteriorly. The interval capsule and ligamentalso extend inferiorly to the superior margin of the sub-scapularis, and project laterally to insert on the greaterand lesser tuberosities. The superior glenohumeralligament also is a contributor to this complex of struc-tures, originating from the supraglenoid tubercle con-tiguous to the attachment of the long head of the bicepstendon (LHB), and then coursing laterally to insert atthe lesser tuberosity, where it fuses with the coraco-humeral ligament.76 This fused rotator interval capsuleand coracohumeral ligament are important stabilizersand anterosuperior supporting structures for shoulderfunction, and can be conceptualized as a roof over theintra-articular course of the biceps tendon, which isthe deepest structure in the interval. When the intervalcapsule and coracohumeral ligament are disrupted,the shoulder may be susceptible to posterior inferiorsubluxation and instability.76

The biceps brachii functions primarily as a supinatorof the forearm and a flexor of the elbow joint. There aretwo tendinous origins of the biceps muscle. Its role isin stabilizing the humeral head in the glenoid duringabduction of the shoulder.79 The intra-articular portion of


MGHL

SCTAB

BT

SGL

SCT AP

BT

A B

F I G U R E 99-10

Glenohumeral ligaments. A and B, Sagittal oblique MR (TR/TE 600/20 ms) images with fat saturation obtainedafter intra-articular gadolinium injection. The anterior band (AB) (A) and axillary pouch portions (AP) (B) of theinferior glenohumeral ligament can be well seen in this plane when contrast is present. The oblique course ofthe middle glenohumeral ligament is noted (MGL) (A). A small portion of the superior glenohumeral ligament (SGL)is visible (B). BT, biceps tendon; SCT, subscapularis tendon.

099.qxd 17/6/05 12:55 PM Page 3212

the LHB arises from the supraglenoid tubercle (see Figs.99-8, 99-9, 99-10, and 99-12) and the posterosuperiorglenoid labrum. It runs across the superomedial aspectof the humeral head and enters the intertubercularsulcus which is formed by the greater tuberosity, lessertuberosity, and soft tissues, including the insertion of thesubscapularis tendon and coracohumeral ligament.79 Itpenetrates the rotator cuff between the supraspinatusand subscapularis at the rotator interval. The bicepstendon is surrounded by a synovial sheath, which iscontinuous with the synovial sheath of the shoulderjoint (see Fig. 99-6). The anterior relationships of theproximal long head of the biceps include the coraco-humeral ligament, the superior glenohumeral ligament,the anterior supraspinatus tendon, and the subscapu-laris tendon. These are the stabilizers of this portionof the tendon. The tendon is secured within the grooveby the transverse humeral ligament, which passesbetween the tuberosities, over the synovial sheath ofthe tendon. The transverse humeral ligament is formedby a few fibers of the capsule, or as a continuation of thesubscapularis tendon. The biceps tendon mainly func-tions through its distal insertion at the elbow, but alsohas some function at the shoulder where it acts as astabilizer,as well as a humeral head depressor. It is closelyassociated functionally with the rotator cuff. The shorthead of the biceps arises from the tip of the coracoidprocess. The conjoined tendon of the coracobrachialismuscle and the short head of the biceps brachii musclejoin on the tip of the coracoid process.

There are a number of bursae about the glenohumeraljoint. The subdeltoid bursa is the largest bursa in thehuman body (see Fig. 99-7). It is comprised primarily ofa subacromial and subdeltoid portion which commu-nicate. The size and configuration of the subdeltoid bursavaries. The bursa is firmly adherent to the periosteum


TIGH

SC

MGH

SGH

CHL

BTSS

IS

TM

F I G U R E 99-11

Rotator interval structures. Sagittal diagram through the left shouldershowing structures of the anterior interval. The first layer of the intervalincludes the subscapularis (SC) and supraspinatus (SS) tendons, and thecoracohumeral ligament (CHL). Deep to this is the articular capsule (arrow)followed by the superior glenohumeral ligament (SGH) and the bicepstendon (BT) and its sheath. Also shown is the infraspinatus (IS), teres minor(TM), middle glenohumeral ligament (MGH), inferior glenohumeralligament (IGH), and triceps long head (T).

A B

F I G U R E 99-12

Biceps tendon. A, Coronal oblique MR images (TR/TE 600/20 ms) with fat saturation obtained after intra-articulargadolinium injection. B, Corresponding anatomic section. The long head of the biceps tendon is seen extending fromthe supraglenoid region into the intertubercular groove (arrows in A and B).

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of the undersurface of the acromion, coracoacromialligament, and superior surface of the rotator cuff. Itslateral extent projects deep to the deltoid muscleapproximately 3 cm along the outer margin of thegreater tuberosity. Medially, the bursa exhibits consider-able variability extending as far as 2 cm medial to theacromioclavicular joint. Anteriorly, the bursa covers thesuperior aspect of the bicipital groove; posteriorly, thebursa extends between the deltoid muscle and rotatorcuff musculature. There is continuity between thesubdeltoid and subacromial components. The bursa is asynovial-lined potential space within a fine layer ofmature areolar/adipose tissue that lubricates motionbetween the rotator cuff and the acromion andacromioclavicular joint; hence it is often inflamed inpatients with impingement and rotator cuff disease. Itonly communicates with the joint if a full-thickness tearof the rotator cuff opens through the joint capsule intothe floor of the bursa.

The subcoracoid bursa resides between thesubscapularis tendon and the combined tendon of thecoracobrachialis and the short head of the bicepstendon. It is identified in nearly 97% of gross specimens,and communicates with the subdeltoid bursa in 11% ofanatomic specimens.80 The subcoracoid bursa shouldnot communicate with the glenohumeral joint. Sub-coracoid bursitis may be a rare cause of nonspecificanterior shoulder discomfort.

The subscapularis bursa is found in up to 90% ofthe population (see Figs. 99-8 and 99-9). It is really anoutpouching of the glenohumeral joint protrudingbetween the superior and middle glenohumeral liga-ments and residing between the posterior aspect of thesubscapularis muscle/tendon and the anterior surface ofthe scapula. The opening into the bursa between thesetwo ligaments is known as the foramen of Weitbrecht.The subscapularis bursa communicates with the jointcavity and protects the subscapularis tendon as it passesunder the coracoid, or over the neck of the scapula. Thesubscapularis recess may extend anterior to thesubscapularis tendon and acts as a gliding mechanism forit (see Fig. 99-9).

Acromioclavicular Joint

The acromioclavicular joint is a small, immobile synovialarticulation between the medial aspect of the acromionand the lateral portion of the clavicle (see Figs. 99-6 and99-7). The articular surfaces of the acromion and clavicleare covered with fibrocartilage. In the central portion ofthe joint there is an articular disk which is fibrocar-tilaginous. A synovium-lined articular capsule surroundsthe joint. It is reinforced by the superior and inferioracromioclavicular ligaments. The inferior portion of thejoint is also reinforced by fibers of the coracoacromialligament.50 The coracoclavicular ligament is moreimportant to stability and forms a fanshaped ligamentcomplex that connects the base of the coracoid processto the overlying clavicle. This ligament has two com-ponents, the posteromedial conoid and anterolateraltrapezoid ligaments.

The coracoacromial arch (see Fig. 99-6) is a strongbony and ligamentous arch that protects the humeralhead and rotator cuff tendons from direct trauma.59 Itconsists of the acromion, acromioclavicular joint,coracoid process, and coracoacromial ligament. Portionsof the rotator cuff tendons, including the supraspinatustendon and the superior 20% of the infraspinatus andsubscapularis tendons, pass under this arch as theyextend to their insertion on the humerus.50 The coraco-acromial ligament is unyielding. It limits the spaceavailable to the rotator cuff, subdeltoid bursa, and bicepsin overhead motion. The ligament can vary in appear-ance.81 In approximately two-thirds of subjects theligament morphology follows the classical description; astrong, fibrous, triangular-shaped structure comprisingtwo conjoined or closely adjacent bands. In the otherthird of cases, the base of the ligamentous triangle isbroadened and extends posteriorly all the way to thebase of the coracoid. This broad acromial insertion siteis thought to be worsened with certain acromial shapes,thickening of the coracoacromial ligament, and bonyosteophytes on the anterior acromion or acromioclav-icular joint. This may then contribute to the process ofchronic impingement.

Acromial morphology has been categorized utilizingplain radiographic analysis: type I flat, type II curved, andtype III hooked (Fig. 99-13).82-84 This configuration canbe assessed with sagittal MR images, though this has metwith variability and poor reliability among investi-gators.85,86 The J- or hook-shaped type III morphologyhas the highest association with impingement syndromeand rotator cuff abnormalities.87

The coracohumeral ligament originates from thelateral margin of the base of the coracoid process,blendswith the supraspinatus tendon, and attaches to both thegreater and lesser tuberosities, creating a tunnel for thebiceps tendon. This ligament stabilizes the long head ofthe biceps tendon and also projects within the rotatorinterval (see Fig. 99-11).88,89

The suprascapular notch lies just lateral to the base ofthe coracoid process. The superior transverse scapularligament converts the notch to a foramen through whichthe suprascapular nerve passes. The suprascapular vesselsproject superior to this ligament.50

MRI Anatomy (Figs. 99-14 to 99-16)

The normal MR appearance of the shoulder in the axial,coronal oblique and sagittal oblique planes is illustratedin Figures 99-14 to 99-16. In the normal state, subcuta-neous fat, intermuscular fat planes, and bone marrownormally have the highest signal on short TR/TE orlong TR short TE images, due to their relatively shortT1. On long TR/TE images, they are of intermediatesignal intensity. Muscles and hyaline cartilage have anintermediate-to-high signal intensity on all spin-echopulse sequences, and on gradient-echo sequences articu-lar cartilage tends to have high signal intensity. Due toa relative lack of mobile protons, a long T1, and a shortT2, certain structures should have essentially a very


099.qxd 17/6/05 12:55 PM Page 3214


F I G U R E 99-13

Acromion shape. Three types of anterior acromion:type 1, flat; type 2, curved; type 3, hook shaped.(Reproduced with permission from Zlatkin MB: MRI ofthe Shoulder, 2nd ed. Philadelphia, Lippincott, Williamsand Wilkins, 2003.)

ANTERIOR

LATERAL

infraspinatustendon

supraspinatusm.

scapular spine

deltoid

A

ANTERIOR

LATERAL

humeralhead

labrum,superior supraglenoid

tubercle

infraspinatustendon

supraspinatustendon biceps tendon

long & short heads

coracoidprocessSGHL

B

ANTERIOR

LATERAL

infraspinatustendon

supraspinatustendon

biceps tendon,long head

coracoidprocess

pectoralis minortendon & muscle

labrum,anterosuperior

labrum,posterosuperior

glenoid

deltoidarticularcartilage

SGHL

C

F I G U R E 99-14

A-C, Axial MRI and MR arthrographic anatomy. Superior to inferior.Short TR/TE images (800/20 ms). IGHL, inferior glenohumeral ligament;MGHL, middle glenohumeral ligament; SGHL, superior glenohumeral liga-ment; a., artery; m., muscle; n., nerve; t., tendon. (Prepared by StevenNeedell, MD; reproduced with permission from Zlatkin MB: MRI of theShoulder, 2nd ed. Philadelphia, Lippincott, Williams and Wilkins, 2003.)

Continued

099.qxd 17/6/05 12:55 PM Page 3215


infraspinatusm.

suprascapular a. & n.in spinoglenoid notch

labrum,posterior

greatertuberosity

lessertuberosity

ANTERIOR

LATERALsubscapularis tendon

subscapularisbursa

labrum,anteriorarticularcartilageglenoid

MGHL

pectoralismajor

biceps tendon, long headstransverse ligament

D

labrum,anterior

LATERAL

MGHL

ANTERIOR

long head ofbiceps tendon

in intertuberculargroove

subscapularistendon

labrum,posterior

corachorachialism.

pectoralis minorm.

subscapularism.

infraspinatustendon

& muscle

E

LATERAL

IGHL, anterior band

ANTERIORtransverse ligament

biceps tendonsubscapularis

tendon

labrum,anteroinferior

articularcartilage

labrum,posteroinferior

teres minortendon

& muscle

F

LATERAL

pectoralismajor m.

ANTERIORbiceps tendon,

long headcoracobrachialis

m.

subscapularistendon &muscle

labrum,anteroinferior

teres minorm.

deltoid

labrum,inferior

G

F I G U R E 99-14, cont’d

D-G, Axial MRI and MR arthrographic anatomy. Superior to inferior. Short TR/TE images (800/20 ms). IGHL, inferior glenohumeral ligament; MGHL, middleglenohumeral ligament; SGHL, superior glenohumeral ligament; a., artery; m., muscle; n., nerve; t., tendon. (Prepared by Steven Needell, MD; reproducedwith permission from Zlatkin MB: MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott, Williams and Wilkins, 2003.)

099.qxd 17/6/05 12:55 PM Page 3216


coracoidprocess

biceps tendon,short head

clavicle

deltoidm.

coracobrachialism.

subscapularistendon &muscle

brachial plexus

axillary vessels

A

SUPERIOR

claviclebiceps-labral

complex

greatertuberosityof humeral

head

bicepstendon,

long head

coracobrachialism.

subscapularis tendon &

muscle MEDIAL

supraglenoidtubercle

supraspinatusm.supraspinatus

tendon

B

labrum,superiorclavicleacromion


coracobrachialism.

brachialartery

subscapularism.

IGHL

supraspinatusm.

MEDIAL

SUPERIOR

suprascapularartery & nerve

coracoacromialligament

supraspinatustendon

C

suprascapularartery & nerve in

spinoglenoid notchacromiondeltoidmuscle

supraspinatusm.

subscapularm.

IGHL

humeralhead


glenoid

supraspinatustendon

D

F I G U R E 99-15

A-D, Coronal oblique MRI and MR arthrographic anatomy. Anterior to posterior. Short TR/TE images (800/20 ms). IGHL, inferior glenohumeral ligamentMGHL; middle glenohumeral ligament; SGHL, superior glenohumeral ligament; subscap, subscapularis; pect., pectoralis; m., muscle; t., tendon. (Preparedby Steven Needell, MD; reproduced with permission from Zlatkin MB: MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott, Williams and Wilkins, 2003.)

Continued

099.qxd 17/6/05 12:55 PM Page 3217

low or no MR signal. These structures include corticalbone, glenoid labrum, fibrous capsule, glenohumeral andother ligaments and tendons, such as the tendinousinsertions of the rotator cuff musculature, and long headof biceps tendon,as it courses in the bicipital groove.90,91

Numerous studies have shown that signal may bepresent in the ligaments, tendons, and fibrocartilage ofasymptomatic people due to age-related degeneration,subclinical pathology,partial volume averaging of normaltissues, or artifacts including magic angle effects.92-99

Axial images (Fig. 99-14) demonstrate the relationshipbetween the humeral head and glenoid fossa. Articularcartilage and the glenoid labrum are well depicted. Thesuperior and middle portions of the anterior glenoidlabrum are usually triangular in this plane, whereas themore anterior inferior labrum may be round. Theanterior labrum can be variable in appearance and size,may be rounded or cleaved,or may even rarely be absent(Fig. 99-17).100 The posterior labrum is also said typicallyto be triangular, but may be rounded, flat or absent.101

The normal bright signal of hyaline cartilage at the baseof the labrum should not be mistaken for a tear ordetachment (Fig. 99-17).102 Linear or globular foci ofincreased signal can be observed near the base of thelabrum in normal subjects.103 Magic angle phenomenoncan cause areas of increased signal in the postero-superior/anteroinferior labrum on proton-density– andT1-weighted images. This signal should not approachthat of fluid on T2-weighted images.103-105 On MRI, labral

shape may vary with humeral rotation. Cleaved ornotched101 configurations are normal variants and shouldnot be mistaken for tears. Labral size, shape, and appear-ance are also not necessarily bilateral and symmetric.Partial imaging of the glenohumeral ligaments (see Figs.99-9 and 99-14)106 may also simulate cleavage planesor notches in the labrum, or even tears or avulsedfragments. A similar problem may also occur with partialimaging of the subscapularis tendon. This may bemost notable in the absence of an effusion when theglenohumeral ligaments and subscapularis tendons areclosely applied to the anterior labrum. Superiorly, fluidmay be seen in a sublabral recess or foramen (Fig.99-18).89,107-109 Fluid or contrast beneath the labrum atthe level of the coracoid or below (below the equator orepiphyseal line) is considered pathologic and indicativeof a tear or detachment. The vacuum phenomenon16 iswhere low signal intensity gas is seen intra-articularlyon gradient-recalled echo (GRE) images and shouldnot be mistaken for a labral tear or cartilage lesion. It isaccentuated with the arm in external rotation and islocated superiorly.

The subscapularis muscle and tendon are also wellvisualized in the axial plane (Figs. 99-9 and 99-14). Thesubscapularis recess or bursa is identified in thepresence of synovial fluid. This bursa can extend anteriorto the subscapularis tendon, as well as between thecapsule and posterior surface of the tendon (Figs. 99-9and 99-14). The anterior capsule and its insertion into


SUPERIORinfraspinatus

muscleacromiondeltoidmuscle

MEDIAL

labrum,posterior

teres minormuscle

subscapularismuscle

trapeziusmuscle

infraspinatustendon

E

deltoidmuscle

humeralhead

teres minortendon

SUPERIOR

scapular spine

Infraspinatusmuscle MEDIAL

teres minormuscle

F

F I G U R E 99-15, cont’d

E and F, Coronal oblique MRI and MR arthrographic anatomy. Anterior to posterior. Short TR/TE images (800/20 ms). IGHL, inferior glenohumeral ligamentMGHL; middle glenohumeral ligament; SGHL, superior glenohumeral ligament; subscap, subscapularis; pect., pectoralis; m., muscle; t., tendon. (Preparedby Steven Needell, MD; reproduced with permission from Zlatkin MB: MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott, Williams and Wilkins, 2003.)

099.qxd 17/6/05 12:55 PM Page 3218


scapularspine

clavicle

supraspinatusm.

suprascapularnerveinfraspinatus

musclesubscapularis

muscle

POSTERIORANTERIOR

coracoid

A

claviclespine ofscapula

deltoidinfraspinatus

muscle

posteriorband, IGHL

teres minormuscle

subscapmuscke

pectoralismajor

MGHL

SGHL

deltoid

glenoidfossa

cephalic v.

POSTERIORANTERIOR

coracoid

anteriorband, IGHL

subscap t.

B

ANTERIOR

acromion

deltoidHH

MGHLSGHLIGHL

infraspinatusm.

supraspinatusm.


pect. minor teres minorm.

POSTERIORclavicle

coraco-humeralligament

coracoid

pect. minortendon

C

acromionsupraspinatus

tendon & muscleANTERIOR

deltoid

humeralhead

teresminor deltoid

SGHL

POSTERIOR

infrapinatustendon &muscle


transverseligament

subscapularistendon

D

humeralhead

deltoid deltoid

POSTERIOR

infraspinatustendon

teres minortendon

supraspinatustendon

ANTERIOR

subscaapularistendon

bicepstendon

E

F I G U R E 99-16

A-E, Sagittal oblique MRI and MR arthrographic anatomy. Medialto lateral. Short TR/TE images (800/20 ms). IGHL, inferior gleno-humeral ligament; MGHL, middle glenohumeral ligament; SGHL,superior glenohumeral ligament; subscap, subscapularis; pect.,pectoralis; m., muscle; t., tendon. (Prepared by Steven Needell, MD;reproduced with permission from Zlatkin MB: MRI of the Shoulder, 2nded. Philadelphia, Lippincott, Williams and Wilkins, 2003.)

099.qxd 17/6/05 12:55 PM Page 3219


BA

F I G U R E 99-17

Labral shape and variation. Axial short TR/TE (800/20 ms) images. A, Triangular appearance of the anterior labrum(short arrow) and the smaller more round appearance of the posterior labrum (arrowhead). The hyaline articularcartilage undercutting the posterior labrum is also seen (long arrow). B, Image reveals the small near absent anteriorlabrum (arrowhead) and the posterior labrum (arrow) to be larger and more triangular. (Prepared by Steven Needell,MD; reproduced with permission from Zlatkin MB: MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott, Williams andWilkins, 2003.)

SLFMGHL

ASL

BT

SLS

A

C

B

F I G U R E 99-18

Sublabral foramen. A, Axial spoiled gradient-echo imageand B, sagittal oblique MR arthrogram with short TR/TEimage (800/20 ms) and fat suppression. High signal con-trast outlines a smooth appearing sublabral foramen(short arrow in A and B). A thick middle glenohumeralattaches anterosuperiorly (long arrow in B). Note thereis no sublabral sulcus more superiorly. C, Lateral viewillustrates the sublabral foramen. It is anterior andinferior to the sublabral sulcus. ASL, anterior superiorlabrum; BT, long head of the biceps tendon; MGHL,middle glenohumeral ligament; SLF, sublabral foramen;SLS, sublabral sulcus. (Drawn by Salvador Beltran; repro-duced with permission from Zlatkin MB: MRI of the Shoulder,2nd ed. Philadelphia, Lippincott, Williams and Wilkins, 2003.)

099.qxd 17/6/05 12:55 PM Page 3220

the glenoid margin can be identified on axial images.It is best seen on long TR/TE images in the presence ofjoint fluid, with gradient-echo imaging, or with MRarthrography. The glenohumeral ligaments may not beeasily separated from the subscapularis tendon onroutine spin-echo axial images but are more easilyidentified when an effusion is present. They may alsobe better seen with MRI arthrography (Figs. 99-9 and99-14 to 99-16). On superior sections, the superiorglenohumeral ligament and superior capsule may beseen inserting into the supraglenoid region, where thesuperior labrum and biceps tendon may be identified.At the midglenoid level the middle glenohumeralligament is best identified posterior to the subscapu-laris tendon and the capsule. At the inferior portion ofthe glenoid cavity the inferior glenohumeral ligamentinserts as a thick complex with the inferior capsuleinto the labrum. When an effusion is present or withMR arthrography the three bands of the inferior gleno-humeral ligament may be identified separately and ofparticular importance in the setting of anterior insta-bility is visualization of the anterior band as it formspart of the anterior inferior labral-ligamentous complex(Figs. 99-9 and 99-14 to 99-16).

The biceps brachii functions as a supinator of theforearm and a flexor of the elbow joint. It is also believedto be a flexor of the shoulder joint. The long head of thebiceps tendon is seen arising from the supraglenoidregion (see Fig. 99-12). At the level of the superior poleof the glenoid, four separate attachments of the bicepstendon may be observed. These include the supraglenoidtubercle, the posterior superior labrum, the anteriorsuperior labrum, and an extra-articular attachment to thelateral edge of the base of the coracoid process. Thebiceps labral complex corresponds to the superior onethird of the glenoid. Stoller has described variability inthe pattern of insertion of the long head into thesupraglenoid region as it forms part of the biceps labralanchor complex.110 As it exits the supraglenoid regionthe tendon courses obliquely and anteriorly over thehumeral head. Proximally it may be best seen on coronaland sagittal oblique images (see Figs. 99-15 and 99-16). Itthen courses inferiorly into the intertubercular groove,where it is well seen on axial sections and appears as around signal void (see Fig. 99-14). Its synovial sheathis seen as a ring of moderate signal intensity,110 whichoften contains a small amount of fluid as a normalfinding.111

The tendons of the rotator cuff complex are well seenon serial coronal oblique images,since this plane coursesparallel to the supraspinatus muscle and tendon (see Fig.99-15). The infraspinatus and teres minor tendons arealso well delineated in this orientation. The subscapularistendon is identified on more anterior coronal obliqueimages but is better evaluated on axial images (Fig.99-14 and 99-15). It may also be delineated on sagittaloblique images (Fig. 99-16). The subdeltoid bursa is apotential space and therefore is not visualized as aseparate structure, unless filled with fluid, though onoccasion a thin rim of fluid signal may be seen on fat-suppressed images in this region.17,74 The subdeltoidperibursal fat plane112 is seen on short TR/TE and

proton-density–weighted sequences, as a high signalintensity line separating the rotator cuff tendons fromthe acromioclavicular joint, acromion, and overlyingdeltoid muscle.

On anterior coronal oblique images, the coraco-clavicular (coronoid and trapezoid) and acromioclavicu-lar ligaments, as well as the acromioclavicular joint, maybe identified. The anterior acromion can be seen. Thecoracoacromial ligament may also be delineated, thoughless constantly identified. The anterior edge of thesupraspinatus tendon can be depicted, along with thelong head of the biceps tendon and the subscapularismuscle and tendon. The rotator interval may be seen onthese sections as well (see Fig. 99-15). The superior andinferior labrum can be identified in this plane as can theaxillary recess.

The sagittal oblique plane demonstrates the rotatorcuff muscles and tendons in cross section (see Fig.99-16). The anteroposterior extent of the rotator cufftendons can be visualized. The relationship of theacromion process, the acromioclavicular joint, and thecoracoacromial ligament to the supraspinatus and othercuff tendons is best depicted. The shape of the anterioracromion can be discerned on sagittal oblique images.With fluid in the joint or with MRI arthrography (seeFigs. 99-10 and 99-16), the labrum, capsule, and gleno-humeral ligaments can be depicted, and in particular thethree limbs of the inferior glenohumeral ligament arewell seen.

The rotator interval may be well evaluated on obliquesagittal images (see Fig. 99-16). The coracohumeralligament is an important landmark on sagittal images,coursing from the coracoid process into the intervalto blend with the interval capsule. The most proximalportion of the biceps can be found immediately inferiorand deep to the posterior aspect of the coracohumeralligament and interval capsule at the level of the superiorbiceps labral anchor complex. The fused coracohumeralligament and capsule may be followed posterosuperiorlyto the level of the anterior margin and leading edge ofthe supraspinatus.76 The long head of the biceps tendonshould be demonstrated as a smooth low signal intensitystructure which on sequential sagittal images (see Fig.99-18) can be followed within the rotator interval frommedial to lateral to the bicipital groove, after which axialimages are best for following the tendon from theproximal bicipital groove (see Fig. 99-14) more distallyalong the humeral shaft.76

Although a detailed discussion of anatomic pitfallsabout the glenohumeral joint is beyond the scope ofthis chapter, those about the anterosuperior labrum areso common and give rise to so many difficulties ininterpretation that they warrant separate discussion. Theanterosuperior labrum is the most common site ofnormal anatomic variations, with specific variationsdescribed in up to 13.5% of those studied.27,107,109 Thesevariations in labral attachment occur above the equatorof the glenoid, which occurs at the 3 o’clock positionon the glenoid margin. Below the equator the labrumshould be firmly attached. The anterosuperior labrum isnot attached to the bony glenoid in 8% to 12% of thepopulation, referred to as a sublabral foramen, also


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known as a sublabral hole (see Fig.99-18).113 This findingis located anterior to the biceps-labral complex.114 Asublabral recess, also referred to as a sublabral sulcus, isa recess/synovial reflection between the biceps-labralcomplex and the superior margin of the glenoid.113 Onoccasion, a sublabral recess can be continuous with asublabral foramen.114 In cadaver studies, a sublabralrecess has been demonstrated in up to 73% of shoulders.115

The anterosuperior labrum can also be focally absent,usually associated with a thickened, cordlike middleglenohumeral ligament. This entity is referred to as theBuford complex,believed to be present in approximately1.5% of patients (Fig. 99-19).114 Pathologic lesions occur-ring or originating in, or extending into, the antero-superior labral quadrant can also be distinguished fromnormal anatomic variations if they extend below thelevel of the coracoid process tip (which helps mark theequator) towards or into the anteroinferior labrum, orposteriorly into the posterosuperior quadrant (beyondthe biceps labral anchor).103 Therefore,a Buford complexshould be suspected if the contiguous anteroinferior

and superior labrum appear normal.116 Morphologicalterations help to distinguish pathologic lesions as well.MR arthrography will delineate this anatomy to betteradvantage and help distinguish variant anatomy frompathologic lesions.

ROTATOR CUFF DISEASE

Pathophysiology

A variety of different factors are considered to beimportant in the etiology of rotator cuff disease andultimately rotator cuff tears. The most discussedmechanisms include rotator cuff impingement beneaththe coracoacromial arch (extrinsic impingement), andprimary degeneration of the cuff. Trauma, overuserelated to occupational and athletic activities, andglenohumeral joint instability also play a role. Acute andchronic inflammation such as seen in rheumatoidarthritis is a less common cause.


A

B

C

F I G U R E 99-19

Buford complex. A, Axial and B, sagittal oblique MRarthrograms. Short TR/TE images (800/20 ms) with fatsuppression. The labrum is nearly absent antero-superiorly (arrowhead on A). The thick cordlike middleglenohumeral ligament is identified partially in A and con-tinuously in B, attaching to the superior labrum directly(arrow). C, Lateral view of the Buford complex. Note theabsent anterior superior labrum and the thick, cordlike,middle glenohumeral ligament which is attachinganterosuperiorly. BT, long head of the biceps tendon;MGHL, middle glenohumeral ligament. (Drawn bySalvador Beltran; reproduced with permission from ZlatkinMB: MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott,Williams and Wilkins, 2003.)

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Impingement

Rotator cuff impingement may be divided into primaryextrinsic impingement, secondary extrinsic impinge-ment (secondary to instability), internal impingement(posterosubglenoid), and subscoracoid impingement.

Primary Extrinsic Impingement

Neer117-120 is most responsible for popularizing thisconcept and using this as an aid in clinical managementof patients. Neer119,120 showed that when the shoulderelevates in its functional arc the rotator cuff andsurrounding soft-tissue structures impinge in the spacebeneath the coracoacromial arch. Neer119,120 stated that95% of rotator cuff tears occur as a result of chronicimpingement beneath this arch. The space below thisarch is defined by the acromion superiorly, the coraco-acromial ligament superomedially, and the coracoidprocess anteriorly. Known sites of impingement in thisarch include the anteroinferior edge of the acromion, thecoracoacromial ligament, and, occasionally, the under-surface of the acromioclavicular joint.121

Variation in anterior acromion shape also correlateswith cuff tears (see Fig. 99-13).83,122-124 Three types ofacromion have been described, based on their shape. Atype 1 acromion has a flat surface, type 2 has a curvedundersurface, and type 3 has a hooked undersurface. Afourth type of acromion shape (type 4) has also beenrecently described. This has a convex inferior surface.124

As yet no statistical correlation has been found betweenthis type of acromion and impingement.

The hook-shaped acromion (type 3) has been shownto have the most significance (see Fig. 99-13).83,122 It hasthe highest correlation with rotator cuff pathology and

particularly rotator cuff tears. Correlation with surgicaland arthrographic results revealed a 70% to 80%association of rotator cuff tears with type 3 acromions.83

Lateral or anterior downward sloping of the acromion,relative to the distal clavicle may also contribute toimpingement and narrowing of the suprapinatus outlet(Fig. 99-20).125 A low lying acromial position, relative tothe distal clavicle, may decrease the space between theacromion and the humerus and may predispose certainindividuals to shoulder impingement.

Osteophytes arising from the acromioclavicular jointand extending inferiorly may play some role in theimpingement process as well. A study by Petersson etal121 revealed an association between the acromio-clavicular joint osteophytes and supraspinatus tendonpathology. Kessel and Watson126 found these changes inone third of their patients with a “painful arc syndrome”and lesions of the supraspinatus tendon. In this studythese osteophytes were found to be more common thananterior subacromial spurs, though they frequentlyoccur together. Osteoarthritis of the acromioclavicularjoint, however, may be identified on MRI examination ina large percentage of asymptomatic individuals.111

Spurs on the anterior and inferior aspect of theacromion are also important.119 These spurs extend fromthe anteroinferior surface of the acromion in a medialand slightly inferior direction toward the coracoidprocess. They arise at the acromial attachment of thecoracoacromial ligament. The presence of these spurs isconsidered presumptive evidence of shoulder impinge-ment. Spur size may be strongly associated with theincidence of a rotator cuff tear.127 Subacromial spurs areconsidered to be a more correlative marker of impinge-ment changes and rotator cuff disease128 than acromio-clavicular joint osteophytes. Variation in size and


A B

F I G U R E 99-20

A, Lateral downsloping (LD) of the anterior acromion as seen on coronal section (arrow). B, Coronal T2-weighted MRI with fat suppressionrevealing LD (arrow). Note the corresponding alterations on the bursal surface of the rotator cuff and the thickened subdeltoid bursa filledwith fluid (arrowheads). (Drawn by Salvador Beltran; reproduced with permission from Zlatkin MB: MRI of the Shoulder, 2nd ed. Philadelphia,Lippincott, Williams and Wilkins, 2003.)

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thickness of the coracoacromial ligament, especiallythe wide portion inferior to the acromion, may be anadditional factor in narrowing the subacromial space andthus causing attritional changes of the rotator cuff.129

An unfused apophysis of the anterior acromion,known as the os acromiale, may contribute to shoulderimpingement.130-132 These normally fuse by 25 years ofage.Fusion failure may occur in 8% of the population andthus form an os acromiale.133 The os acromiale may causeimpingement because, if it is unstable, it may be pulledinferiorly during abduction by the deltoid, whichattaches here. In addition,hypertrophy and spurring maydevelop at the junction of the os acromiale and the moreposterior aspect of the acromion along its undersurface,and may contribute to impingement and subsequentrotator cuff tears in this manner.134

The clinical syndrome of impingement was outlinedby Neer.119 He described the technique of anterioracromioplasty to relieve the symptoms of impingement.Three progressive stages of impingement lesions weredescribed. This was based on the age of the patient, thetype of activity that presumably led to the injury, and thepathologic findings. Stage 1 typically results fromexcessive overhead use such as in sports. It usuallyoccurs in patients younger than 25 years of age, but mayoccur at any age. Histologically, edema and hemorrhageare said to be present in the rotator cuff tendons at thisstage. If treated conservatively, this phase of the diseaseis usually reversible and these patients may return tonormal function.

Stage 2 disease consists of fibrosis and thickening ofthe rotator cuff tendons as well as the subacromial-subdeltoid bursa. It occurs in patients between 25 to40 years of age and is less common than stage 1. Theshoulder will usually become symptomatic aftervigorous overhead use such as in throwing sports.Traditionally, surgery is considered in these patientswhen a conservative approach to therapy has failed. Theprocedure at this stage is removal of the thickenedsubacromial bursa and dividing the coracoacromialligament. According to Neer,119,120 anterior acromio-plasty in this group of patients who are younger than40 years old should not be performed unless overhangand prominence of the undersurface of the anterioracromion is present.

Stage 3 results from further impingement wear. At thisstage incomplete (3A) or complete tears (3B) of therotator cuff are present. These lesions are most commonin patients older than 40 years of age. Lesions of thebiceps tendon are usually present, though true tears ofthe biceps tendon are much less common than theassociated cuff tears. Secondary bone changes are verycommon. Acromioplasty and cuff repair are oftenrequired.

Secondary Extrinsic Impingement (ImpingementAssociated with Instability)

Fu et al134 subdivided impingement syndromes into twomajor categories: primary extrinsic impingement whichoccurs in nonathletic persons and is related toalterations in the coracoaromial arch as discussed earlier;

and secondary impingement occurring mainly inathletes involved in sports requiring overhead motion ofthe arm and which has a relationship to glenohumeraljoint instability.135,136 These patients may developsymptoms without any abnormality of the bony anatomyof the coracoacromial arch. These patients usuallyhave less advanced rotator cuff pathology, includingtendinosis or partial or very small rotator cuff tears.136

This distinction is important, since therapy should bedirected to the underlying instability. Conservativetreatment is aimed at strengthening the rotator cuff andscapular rotators. Throwing athletes with glenohumeralinstability and secondary impingement that do notrespond to conservative treatment may be treated withan anterior capsular labral reconstruction. In the lesscommon situation where alterations of the bonycoracoacromial arch may also be identified (mixedpathology), then subacromial decompression may benecessary in addition to anterior stabilization.

Posterosubglenoid (Internal) Impingement

This is impingement of the rotator cuff on theposterosuperior portion of the glenoid in throwingathletes.38,137-144 This is also known as internalimpingement. This particular type of impingementoccurs during the late cocking phase of throwingwith abnormal contact between the posterosuperiorportion of the glenoid rim and the undersurface ofthe rotator cuff, and is thought to occur at the extremesof abduction and external rotation. It has also beenrecognized in nonathletes who frequently rotate theshoulder into the extremes of abduction and externalrotation.139,145

A triad of findings will be present including injury tothe rotator cuff undersurface at the junction of theinfraspinatus and supraspinatus tendons, degenerativetearing of the posterosuperior glenoid labrum, as well assubcortical cysts and chondral lesions in the postero-superior glenoid and humerus due to repetitive impac-tion. There may in addition be an injury to the inferiorglenohumeral ligament and anterior inferior labrum.

Subcoracoid Impingement

Impingement beneath the coracoid process relates toencroachment of the subscapularis tendon insertion onthe lesser tuberosity,146-148 secondary to narrowing ofthis space between the coracoid process and the humeralhead. Developmental enlargement of the coracoid pro-cess that projects more laterally may be the underlyingcause.

Subcoracoid impingement may occur when thedistance between the coracoid and lesser tuberositymeasures less than 11 mm, with the arm positioned inmaximal internal rotation.15

Other Causes

These may include such entities as supraspinatus musclehypertrophy in athletes who perform repetitive over-head activity, such as swimmers. In these patients, the


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enlarged supraspinatus muscle belly may seem to bedeformed beneath the acromioclavicular joint oncoronal oblique MR images.149 Impingement may alsooccur related to prominent healed callus from a greatertuberosity fracture.

Primary Rotator Cuff Degeneration(Intrinsic Causes)

There are other theories on the etiology of rotator cufftears and many who disagree with the predominant orexclusive role of impingement in the development ofcuff tears. Codman150,151 suggested that degenerativechanges within the cuff itself lead to tears. This may havea vascular or ischemic basis. Codman150,151 describeda critical portion in the rotator cuff at the distalsupraspinatus tendon approximately 1 cm medial to itsinsertion into the greater tuberosity. Codman150-152

described the pattern of degenerative cuff failure as a“rim rent” in which the deep surface of the cuff is tornat its attachment to the tuberosity. He stated thatthese tears tend to begin on the deep surface andthen extend outward until they become full-thicknessdefects. He pointed out that it would be hard to explainthis on the basis of erosion from contact with theacromion process.

Uthoff et al153-155 found that most rotator cufftears begin from the articular side. They indicated that ifrotator cuff tears arose primarily from extrinsicimpingement, then the majority of rotator cuff tearsshould begin from the bursal side. On the basis of thisthey considered that rotator cuff tears are thereforedegenerative in origin and nature and that extrinsiccauses therefore play a secondary role. Ozaki et al156

have shown in cadavers that the majority of pathologicchanges of the undersurface of the acromion occurred inspecimens in which the cuff tear was incomplete and onthe bursal side of the cuff.

The critical portion in the rotator cuff has beendescribed as “the critical zone.” This region is said to bea watershed area, occurring between osseous and ten-dinous vessels supplying the rotator cuff tendons.153,157

The histologic pattern of age-related degeneration inthe tendon reveals changes in cell arrangement, calciumdeposition, fibrinoid thickening, fatty degeneration,necrosis, and rents. There is an alteration in the patternof collagen fibers in such patients, with transforma-tion from type II to fibrovascular-containing type IIIcollagen.158,159

In contrast, intraoperative laser Doppler flowmetryhas also been used to assess the rotator cuff tendonvascularity in symptomatic patients.160 These studieswere considered to support impingement as a mech-anism of rotator cuff pathology. Particularly in patientswith intact tendons and tendinosis but also in patientswith partial and complete tears, increased vascularitywas found in the region of the critical zone. Brookset al161 also carried out perfusion studies which theyconsidered did not support an ischemic zone in thedistal anterior supraspinatus tendon. They concludedthat factors other than vascularity are important in thepathogenesis of supraspinatus rupture.

Budoff et al162 argued that most patients with rotatorcuff abnormalities have as their primary underlyingetiology intrinsic, rather than extrinsic, impingement,which they believe occurs secondary to rotator cufffailure. They stated that the suprapinatus, since it is asmall and relatively weak muscle, is in a key position andis therefore susceptible to overuse and injury. Wheneccentric tensile overload occurs at a rate greater thanthe ability of the cuff to repair itself, injury occurs,resulting in weakness of the musculotendinous rotatorcuff unit. Trauma to the shoulder may initiate the processas well, and a weak, fatigued or injured rotator cuff isunable to oppose the superior pull of the deltoideffectively, which is then unable to keep the humeralhead centered on the glenoid during elevation of thearm, causing it to elevate, which then functionallynarrows the subacromial space. Continued dysfunctionof the rotator cuff and further superior migration of thehumeral head cause the greater tuberosity and rotatorcuff to abut against the undersurface of the acromionand the coracoacromial ligament, leading to signs ofsecondary extrinsic impingement. These authors believethat changes to the coracoacromial ligament and theundersurface of the anterior acromion are secondaryprocesses, and since they do not occur in many patients,these structures should be preserved if their anatomy isnot altered. They believe that these structures play animportant role as passive stabilizers against superiormigration of the humeral head, and therefore should notbe sacrificed. These authors therefore recommenddebridement of the degenerated cuff tissue arthroscop-ically, and resection only of clearly identified excres-cences. They do not perform a complete acromioplastyand do not remove the coracoacromial ligament.

Trauma

Trauma is considered to play a secondary role in theetiology of rotator cuff tears.119,120 Little force may beneeded to tear a tendon that is already degenerated bylong-standing impingement wear, perhaps related tounderlying tendinosis and repeated episodes of peri-tendinous inflammation. The trauma from a fall ordislocation may, therefore, complete or enlarge a pre-existent small or incomplete tear, or tear an alreadydegenerated tendon.

Notwithstanding the above, a tear may occurfollowing an anterior dislocation of the shoulder, usuallyin an older patient in whom a cuff rupture occurs ratherthan an injury to the glenoid labrum and/or shouldercapsule. Studies show that a cuff tear may occur in 14%to 63% of patients with acute anterior dislocations.The incidence will be higher in older patients.163-166 Thesupraspinatus tendon may tear with variable degrees ofinfraspinatus involvement.

Traumatic tears of the subscapularis tendon mayoccur due to traumatic hyperextension or externalrotation of the abducted arm.167 Concomitant bicepstendon pathologic conditions include subluxation,dislocation, or rupture. Isolated ruptures of the sub-scapularis may also occur with anterior dislocations,again predominantly in male patients older than 40.164,168


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Avulsive fractures of the lesser tuberosity at the siteof insertion of the subscapularis may occur in elderlywomen and men.With a posterior dislocation there maybe disruption of the infraspinatus or teres minortendons.169 Superior dislocations of the humeral headmay also result in cuff rupture as the humeral head isdriven upward acutely through the cuff.

A cuff tear may also arise following a dislocationwhen the greater tuberosity is fractured. It may alsodevelop following an avulsion fracture of the greatertuberosity. Posterior dislocations may also result in afracture of the lesser tuberosity, in which case a tear ofthe subscapularis tendon may result. Although a non-displaced greater tuberosity fracture may result in injuryto the cuff, recent evidence with MRI170,171 indicates thatthis may more often result in a tendon contusion orintact cuff, rather than a tear, and the pain may morecommonly be related to the bony injury.

Classification, Location, and Incidenceof Rotator Cuff Tears

A full-thickness rotator cuff tear extends from thearticular surface to the bursal surface of the cuff. Acomplete tear is one in which the whole thickness ofthe rotator cuff and capsule are torn, resulting in directcommunication between the subdeltoid bursa and thejoint cavity.172 In contrast, partial-thickness tears (Fig.99-21) involve only one surface of the cuff, either theinferior or superficial surface, or only the midsubstanceof the cuff. Tears of the inferior surface are also referredto as deep or articular surface tears, those of themidsubstance as intrasubstance tears, and those ofthe superficial surface as superior or bursal surfacetears. Retraction of tendinous fibers from the greatertuberosity may also be considered a partial tear.96

Partial tears have been classified by Ellman173 asfollows:grade 1 (low grade) are less than 3 mm deep andonly the capsule or superficial fibers are involved; grade

2 (intermediate) are 3 to 6 mm deep and less than 50%of the cuff thickness is involved; and grade 3 (high gradeor deep) greater than 6 mm, in which more than 50% ofthe cuff thickness is involved.

Complete cuff tears can be classified by size. Smalltears are less than 1 cm,medium tears are less than 3 cm,large tears are 3 to 5 cm, and massive tears are greaterthan 5 cm.174 Ellman175 proposed that the area of a tearbe measured in square centimeters using the base of thetear along the former insertion site times the depth ofthe muscle retraction. The size of the rotator cuff tear inboth anterior posterior and mediolateral dimensions is avery important prognostic factor in determining surgicaloutcome.176

Most partial and small full-thickness rotator cuff tearsare centered in the anterior half of the supraspinatus.177

Supraspinatus tears begin on the deep surface anteriorlyand distally at the greater tuberosity insertion, near thebiceps tendon, and then extend outward until theybecome full-thickness defects. Once in the supraspinatusthe defects then propagate posteriorly and mediallythrough the remaining portions of the supraspinatus andthen into the infraspinatus. This then puts progressivestress on the biceps tendon. Changes in the bicepstendon may initially be of a less severe degree, and mayonly consist of tendinosis, but it may eventually rupture,especially in chronic defects. The defect may thenpropagate across the bicipital groove to involve thesubscapularis tendon, starting at the top of the lessertuberosity and extending inferiorly.

Involvement of the subscapularis tendon may occurwith larger tears and anterior tears. In this case it mayoften involve the superior articular surface fibers and therotator interval capsule. It may also be involved insubcoracoid impingement. Acute ruptures of thesubscapularis can occur with severe trauma,or in elderlypatients with recurrent anterior dislocations. As thelesions propagate anteriorly into the subscapularisthey may result in medial dislocation of the bicepstendon.75,167,168,178-182


A B C

F I G U R E 99-21

Classification of partial tears by location. A, Articular surface partial tear; B, bursal surface partial tear; and C, intrasubstance(interstitial) partial tear. (Drawn by Salvador Beltran; reproduced with permission from Zlatkin MB: MRI of the Shoulder, 2nd ed.Philadelphia, Lippincott, Williams and Wilkins, 2003.)

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Isolated infraspinatus full-thickness tears areuncommon. They can occur in the spectrum of posteriorsuperior (internal) subglenoid impingement or withsevere trauma with posterior dislocation. Partial tearsoccurring at the junction of the posterior supraspinatusand anterior infraspinatus can occur in overheadthrowing athletes in association with posterior superior(internal) subglenoid impingement.141 Tears of the teresminor tendon are distinctly rare, even in the setting ofmassive tears, though partial tears of the superior aspectof the teres minor have been reported in a series ofmassive, irreparable, rotator cuff tears.183 They may occurwith trauma, in association with posterior capsularrupture as well as infraspinatus tendon tears, or in thesetting of a posterior dislocation. In this situation, teresminor muscle and capsular injuries may occur withoutthe typical reverse Bankart lesion.184

With progressive disruption of the rotator cufftendons, the humeral head can then rise under the pullof the deltoid muscle. This then leads to abrasion ofthe humeral head articular cartilage against the coraco-acromial arch, causing subacromial impingement that intime erodes the anterior portion of the acromion and theacromioclavicular joint. There are also nutritional factorsrelated to the rotator cuff tear that cause atrophy of theglenohumeral articular cartilage and osteoporosis of thesubchondral bone of the humeral head. Eventually, thesoft, atrophic head collapses, producing the completesyndrome of rotator cuff tear arthropathy.185,186

One other factor that is important when evaluatingrotator cuff tears is the assessment of the status of thetorn rotator cuff tendon edges.On imaging examinationsas well as at surgery the appearance of the torn edgesmay be classified as good, fair or poor.187,188 The status ofthe rotator cuff musculature with regard to the degree ofatrophy, as well as fatty infiltration, can be also bequantified in a relative manner as mild, moderate, orsevere.187,188 Another system classifies both atrophy andfatty infiltration. Goutallier et al189,190 graded muscularfatty degeneration into five stages in patients withrotator cuff tears.

Magnetic Resonance Imaging

Bone Changes Associated withExtrinsic Impingement

The most common secondary bone changes that havebeen described in association with extrinsic impinge-ment include acromioclavicular joint osteophytes,subacromial spur formation, and cysts and sclerosis inthe greater tuberosity.

Subacromial spurs are less common but are morecorrelative of rotator cuff disease than acromioclavicularosteoarthrosis (Fig. 99-22).111 They are the most specificfinding on MR examination for shoulder impingement.191

Small subacromial spurs may appear on MRI exam-ination as a signal void that projects from the acromiontip in a medial and inferior direction, and may besurrounded by a rim of signal void representing corticalbone,192 and must be distinguished from the insertion of

the coracoacromial ligament or the deltoid insertion.99

The inferior tendon slip of the deltoid inserts on theinferolateral acromion, coracoacromial ligament, andinferomedial acromion.99 Larger spurs frequently containmarrow and thus have brighter signal.193 The anteriorand inferior location of the spurs are often best shownon sagittal oblique images. Larger spurs may be evidenton coronal oblique images.

Degenerative osteophytes of the acromioclavicularjoint have similar appearances. They may be inferiorlyprojecting. These osteophytes of the acromioclavicularjoint may precede the presence of anterior acromialspurs. Hypertrophy and callus formation of theacromioclavicular joint capsule may also be visualized,which appears as a rounded mass of medium signalintensity surrounding the joint, which often projectsinferiorly194-196 and may encroach on the bursal surfaceof the musculotendinous junction of the supraspinatus.The relationship of the acromioclavicular joint arthrosisto the subacromial space and bursal surface of the cuffare best seen on the sagittal oblique and coronal obliquesequences (see Figs. 99-15 to 99-18). Fluid may be seenin the acromioclavicular joint, especially on fat-saturatedimages, and there may also be increased signal on thesefat-saturated images in the bony margins of this joint. Thesignificance of fluid within the acromioclavicular jointhas also been debated, however.195,197,198 It is speculatedthat marginal edema in the bones about the acromio-clavicular joint may be a marker of this joint as a site orsource of pain in patients with these findings. Edemain the distal clavicle alone may be stress related andmay be particularly common in athletes such as weightlifters, throwers, and swimmers (Fig. 99-23). Low signalintensity sclerosis, erosions, and subchondral cysts arealso identified on MR images in patients with acromio-clavicular joint arthrosis.


F I G U R E 99-22

Sub-acromial spur. Coronal oblique T1-weighted image. Note the matureappearing subacromial spur (arrow).

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The three types of acromion shape described for plainradiographic examination can be adapted for MRI (Figs.99-13 and 99-24). Type 1 has a flat or straight inferiorsurface. Type 2 demonstrates a smooth curved inferiorsurface that approximately parallels the superiorhumeral head in the sagittal oblique plane. Type 3 has aninferiorly curved or hook shape on sagittal images(Fig. 99-24). Type 3 acromions are statistically associatedwith an increased incidence of rotator cuff tears. Studiesthat have used sagittal oblique MRI to determine thepresence of hook-shaped anterior acromions have alsofound an association with clinical impingement androtator cuff tears.199 A type 4 acromion can be appre-ciated on MR examination when the acromion appearsconvex near its distal end.124 Peh et al85 found that theapparent acromial shape is sensitive to the minorchanges in the MR section viewed. More medial sectionscloser to the acromioclavicular joint may falselyproduce the appearance of a hooked anterior acromion,which has a flat appearance on more peripheral sagittaloblique images.

Lateral or anterior downward sloping of theacromion, or a low lying acromion, relative to the distalclavicle may contribute to impingement and narrowingof the suprapinatus outlet, and can be discerned on MRIimages. Impingement related to lateral downsloping ofthe anterior acromion may cause impingement of themid portion of the supraspinatus tendon. It may causeimpingement on the superior aspect of the subscapularistendon.125,200 This type of acromial position may also beassociated with lateral supraspinatus injury near thegreater tuberosity insertion, especially in patients whoperform forceful abduction of the shoulder.196 Anterior

downsloping is best seen on sagittal MR images andlateral downsloping on coronal MR images. Anteriordownsloping of the acromion is present when theanterior inferior cortex of the acromion is more infe-riorly located relative to the posterior cortex on sagittaloblique images. Lateral downsloping is identified whenthe inferior surface of the distal acromion is inferior or


A B

F I G U R E 99-23

Acromioclavicular joint osteoarthritis. A, Coronal oblique and B, sagittal oblique fast spin-echo T2-weighted MRimages with fat suppression. The acromioclavicular joint shows advanced degenerative changes with inferiorlyprojecting spurs, capsular hypertrophy, and marginal edema (arrows).

F I G U R E 99-24

Type 3 acromion. Sagittal oblique fast-spin echo T2-weighted MR imagewith fat suppression. Note the hook-shaped, type 3 acromion (whitearrow). A thickened coracoacromial ligament is also present (black arrow).

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caudally located, relative to the inferior surface of themore proximal aspect of the acromion, adjacent to theacromioclavicular joint (see Fig. 99-20).

Thickening of the coracoacoromial ligament maycontribute to narrowing of the supraspinatus outlet andis best seen on sagittal oblique images (see Fig. 99-24).This includes assessment of its size and whether thethickening is smooth or irregular.129,192,201-203

The os acromiale is identified best on superior axialsections that demonstrate the entire acromion (Fig.99-25A). The synchondrosis should not be mistaken forthe subjacent acromioclavicular joint. When superioraxial sections are not available this pattern of mimickingthe acromioclavicular joint on sagittal and coronaloblique images may also be used to help identify thepresence of the os acromiale (Fig. 99-25B).130,131,204-206

Increased signal on either side of the fusion defect maybe seen on both STIR and fat-suppressed T2-weightedfast spin-echo sequences (Fig. 99-25A). This hyper-intensity may correlate with degenerative changes orinstability of the os acromiale. It is important to identifythe os acromiale because removal of the acromion distalto the synchrondrosis at the time of acromioplasty mayfurther destabilize the synchondrosis and allow for evengreater mobility of the os acromiale after surgery andworsening of the impingment.204

Hypertrophic changes or flattening and sclerosis mayoccur in the region of the greater tuberosity in patientswith impingement. This is likely as noted above to bedue to traumatization of the greater tuberosity on theundersurface of the acromion during abduction. Thesemay be appreciated on MR examination as areas ofcortical thickening or prominent low signal in the regionof the greater tuberosity.149

Humeral head or greater tuberosity cysts have beenassociated with shoulder impingement. This is a verycommon finding on MR examination. More recentlythese cysts, which can become quite large, have beenconsidered to be nonspecific and are as well correlatedwith increasing age as they are with alterations in therotator cuff, reflective of impingement.111 These cystsare often posteriorly located at the greater tuberosity orat its junction with the humeral head near the capsularinsertion. Cysts may also occur more superiorly or ante-riorly as well.149

Tendon Lesions

Tendinosis

A variety of terms may be used to describe the injuredtendon in the absence of a tendon defect. The term mostcommonly used in the past was tendonitis. Most authorsprefer the term tendinosis or tendinopathy as thepathologic changes found within such tendons mostoften do not include inflammation,207-209 except in theperitendinous tissues. The MRI findings of tendinosis(Fig. 99-26) are moderate increase in signal intensitywithin the tendon on short TR/TE and proton-densityimages,oriented along the long axis of the tendon,whichmay be homogeneous (focal, diffuse or bandlike)96 orinhomogeneous, and which fades or is absent on longTR/TE (T2-weighted images) whether obtained withconventional96,187,188,210 or fast spin-echo imagingsequences without fat suppression. Fat-suppressedconventional or fast spin-echo T2-weighted sequences,orSTIR imaging sequences, may make this signal more


A B

F I G U R E 99-25

Os acromiale. A, On this superior axial section the os acromiale is well seen (arrow). Marginal edema is present.B, Posterior coronal oblique images may also identify the presence of the os acromiale (arrow). Note the pseudoacromioclavicular joint, more posterior in location.

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conspicuous and should be distinguished from true fluidsignal as seen in a rotator cuff tear (see Fig. 99-26).188

Tendon thickening may be present, and increased andmore diffuse thickening may be associated with moreadvanced tendinosis. It is proposed that persistence ofincreased signal within the tendon on images with T2weighting, but less intense than fluid signal, may indicatemore advanced tendinosis, related to a greater degree ofcollagen breakdown in the tendon.211

Fat-saturated T2-weighted fast spin-echo images aremore sensitive to the presence of fluid in the subdeltoid

bursa (Figs. 99-27 and 99-28). With the use of thesesequences, identifying fluid in the subdeltoid bursaregion is a more common correlate of disease at thisstage than previously thought.187,188 When evident, fluidis considered to be indicative of associated subdeltoidbursal inflammation. Persistent low signal intensity in athickened subacromial subdeltoid bursa on imagingsequences with both T1 and T2 contrast has also beendescribed96 and is said to indicate proliferative chronicsubdeltoid bursitis, but this appearance is more difficultto discern on MRI studies.


A B

F I G U R E 99-26

Tendinosis. A, Coronal oblique T1-weighted image. Diffuse increased signal in the supraspinatus tendon is present(arrow). The articular and bursal surfaces of the tendon are intact. B, Coronal oblique fast spin-echo proton-density–weighted sequence with fat suppression. Note the relative increase in tendon signal, which can be seen whenfat suppression is present but does not approach fluid signal (arrow).

A B

F I G U R E 99-27

Tendinosis. Articular surface fraying/fibrillation. MR arthrography. A, Coronal oblique fast spin-echo T2-weightedsequence with fat suppression. Moderate tendinosis is seen in the supraspinatus tendon and there is undersurfacefraying and irregularity (arrows). A small amount of fluid is seen in the subdeltoid bursa, likely reflective of bursalinflammation (arrowhead). B, Coronal oblique T1-weighted MR arthrogram with fat suppression outlines theundersurface fraying and irregularity (arrows), but no focal tendon defect is seen.

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The arthroscopic findings in patients with these MRIfindings are hyperemia of the tendon surface and bursalscarring and inflammation.187 Biopsy of the tendon inpatients with MRI findings consistent with tendinosishas been carried out in a small number of patients andhas shown mucoid degenerative changes and someinflammation.212 Histologic sectioning in cadavers withsimilar MRI findings revealed eosinophilic, mucoid, andfibrillary degeneration.94

MR arthrography (Fig. 99-29) may confirm theintegrity of the articular surface of the cuff. In patientswith tendinosis the articular surface should be linear incontour and low in signal intensity.29

Anzilotti et al213 described a subset of young patients(<35 years) with acute, post-traumatic insults to the rota-tor cuff which mimic the signal intensity changes of ten-dinosis. Patients had signal intensity that was similar totendinosis, but was localized more in atypical locationsof the supraspinatus tendon and was associated with bonebruise, suggesting the possibility of post-traumatic strain.

Tendons with a similar MRI appearance to tendinosishave been detected in asymptomatic individuals.97,214,215

They should be distinguished from advanced rotatordisease and rotator cuff tears as they are not associatedwith morphologic alterations and do not brighten likefluid on long TR/TE images.


A B

A B

F I G U R E 99-28

Tendinosis. Bursal surface fraying/fibrillation. A, Coronal oblique fast spin-echo proton-density–weighted image andB, fast spin-echo T2-weighted sequence with fat suppression. Moderate/severe tendinosis is seen in the supra-spinatus tendon and there is bursal surface fraying and irregularity (arrows). A moderate amount of fluid is seen in thesubdeltoid bursa (arrowheads), reflective of bursal inflammation.

F I G U R E 99-29

Tendinosis. MR arthrography. A, Coronal oblique fast spin-echo proton-density–weighted image. Diffuse increasedsignal in the supraspinatus tendon is noted (arrow). The articular and bursal surfaces of the tendon are smooth.B, Coronal oblique T1-weighted MR arthrogram with fat suppression. No contrast-filled tendon defect is seen(arrow).

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Other MRI changes beyond tendinosis, not indicativeof either a partial or complete tear but consideredabnormal, include tendon thinning or irregularity of thetendon surface (see Figs. 99.27 and 99.28). MR arthrog-raphy will outline those findings that occur on thearticular side (see Fig. 99-27B). Such irregularities in con-tour and signal intensity indicate fraying of the super-ficial fibers of the tendon. At arthroscopy the tendonsurface is described as showing “fraying, roughening ordegeneration.”158,187 On the bursal side of the tendon,T2-weighted images, especially with fat suppression,will show some fluid in the subdeltoid bursa that likelyreflects bursal and peribursal inflammation. Thesefindings may be reflective of the wear and tear ofimpingement. The distinction between this stage ofdisease and early partial-thickness tears may be difficultto define both by MRI and at arthroscopy, though bydefinition173 in order to describe a partial tear a discretetendon defect should be seen.

Partial Tears

Using MRI the diagnosis of partial tears is less sensitiveand accurate than for complete tears.3,6,8,96,187,188,216-220 Apartial tear can be diagnosed when there is a defect thatextends to one surface only, either the articular surface(Fig. 99-30), which is more common, or the bursalsurface (Fig. 99-31), or is within the tendon substance(intrasubstance or interstitial), and that shows increasedsignal on long TR/TE images, or on other imagingsequences with T2 contrast.When the increased signal isthat of fluid the diagnosis can be made with confidence.Tears of the bursal surface and of the undersurface willbe perpendicular to the long axis of the tendon oncoronal oblique imaging sequences,whereas those in thetendon substance are parallel to the long axis of thetendon (Fig. 99-32).

Some partial tears may be partially healed or quitesmall and, therefore, the signal increase may not be asstrong. In such situations they may be difficult todistinguish from tendinosis.Fat saturation or STIR imagesmay help (see Figs. 99-30 and 99-32).3,6,210,217,221

T2-weighted fast spin-echo techniques with fat satura-tion can obtain this type of contrast in a more efficientmanner. STIR imaging has also been suggested toincrease diagnostic performance as well. Partial tearsmay less commonly be manifested by significant loss oftendon thickness. T1-weighted images with fat satura-tion after the intra-articular injection of gadoliniumdiethylenetriamine pentetate (Gd-DTPA) are of value inthe diagnosis of partial tears of the articular surface ofthe tendon (Fig. 99-33).19,23,26,32,35,39,222 In this situationMR arthrography maximizes anatomic resolution anddiagnostic confidence. Partial-thickness tears occur andbegin commonly along the undersurface of the antero-distal insertion of the cuff near the “critical zone,” andtherefore evaluating this region of the cuff undersurfacewith MR arthrography is of considerable importance inthe differentiation of a normal cuff and cuff tendino-sis from one with a partial tear. On MR arthrography apartial-thickness tear is diagnosed when contrast extendsin a focal manner into a tendon defect,but does not extendinto the subacromial subdeltoid bursa. MR arthrographyis also very effective at depicting the extent of morphol-ogic alterations and their depth of involvement by show-ing contrast imbibition and the depth of loss of tendonthickness (Fig.99.33). This is again helpful in distinguish-ing these alterations from those associated with tendi-nosis and tendon surface degeneration.

Partial tears associated with posterosuperior sub-glenoid impingement (Fig. 99-34) may have areas ofdelamination of the rotator cuff undersurface and looseflaps of cuff tissue may be seen on the cuff undersurface.These partial tears which commonly occur posteriorly atthe junction of the suprapsinatus and infraspinatus are


A B

F I G U R E 99-30

Articular surface partial tears. A, Coronal oblique T2-weighted image. A high-grade partial tear of the supraspinatustendon undersurface is seen. Note the focal tendon defect outlined by the fluid signal (arrow). B, Sagittal oblique fastspin-echo T2-weighted image with fat suppression in another patient. A deep articular surface defect is againidentified. The addition of fat suppression increases the conspicuity of the lesion (arrow).

099.qxd 17/6/05 12:56 PM Page 3232

sometimes referred to as posterior interval tears.141,143,223

MR arthrography and the arm placed in ABER posi-tion39,141,223 may be useful in such patients. This positionalso allows better depiction of the other lesions in thespectrum of this process, including the osteochondralcompression fracture of the posterosuperior humeralhead, degenerative fraying or tear of the posterosuperiorglenoid labrum and alterations of the subjacent glenoid,and the less common involvement of the inferiorglenohumeral ligament and anterior inferior labrum.

Intrasubstance partial tears are difficult to confirmwith either surgery or arthroscopy, unless the tendon isincised. This diagnosis is considered on MR imageswhen fluid signal is present on long TR/TE images in thesubstance of the tendon, i.e., parallel to the long axis ofthe tendon, and not extending to either the bursal orarticular surface (see Fig. 99-32). Acute tendonitis ortendon contusions after trauma can theoretically have asimilar pattern of increased signal as well. Combinationsof partial tears may also be seen.


A B

F I G U R E 99-31

Bursal surface partial tears. A, Coronal oblique T2-weighted image. An intermediate-grade partial tear of thesupraspinatus tendon superior surface is seen. A focal tendon defect outlined by fluid signal is seen (outlined by shortand long arrows). B, Sagittal oblique fast spin-echo T2-weighted image with fat suppression. Note the fluid signaloutlining a high-grade bursal surface partial tear of the supraspinatus tendon (arrows).

F I G U R E 99-32

Intrasubstance partial tears. Coronal oblique fast spin-echo T2-weightedimage with fat saturation. Longitudinal increased signal in the tendonsubstance approaching that of fluid is seen (arrow). The signal is orientedparallel to the tendon.

F I G U R E 99-33

Partial tears. Coronal oblique T1-weighted MR arthrogram with fatsaturation. A high-grade articular surface partial-thickness tear of thesupraspinatus tendon is seen (arrow). MR arthrography clearly outlines theextent and depth of the tendon defect.

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Fluid in the subdeltoid bursa may commonly beidentified in bursal-side partial-thickness tears and maymake it easier to assess the size and depth of thesetears.82 Bursal-side partial tears cannot be identified withMR arthrography from the articular side. Preliminarywork with MR bursography has the potential to improvethe accuracy for diagnosis of bursal-side partial tears, butas yet has not been used very often in clinical practice.

Retraction of tendinous fibers from the distalinsertion into the greater tuberosity may also beconsidered a partial tear (Fig. 99-35). This may occur inthe throwing athlete, specifically baseball players.224

These lesions appear as small regions of high signalintensity on long TR/TE images in this location, withassociated bony defects on the greater tuberosity. Partialtears of differing size and nature may coexist in differentportions of the rotator cuff or at the posterior margin ofa larger tear.

Full-Thickness Tears

This diagnosis is made with the visualization of acomplete defect in the tendon, extending from the artic-ular to the bursal surface of the tendon, most commonlyinvolving the supraspinatus tendon.3,4,6,82,96,187,188,217,

220,225-229 The defects in the rotator cuff are filled withfluid, granulation tissue, or hypertrophied synovium,and therefore in the majority of cases (80% or greater)with a cuff defect, fluid-like signal is present withinthe defect on long TR/TE images,229 which can be

made more conspicuous with the use of fast spin-echosequences with fat suppression or fast inversion recov-ery sequences (STIR). The presence of a tendon defectfilled with fluid is the most direct and definite sign of arotator cuff tear.

In the presence of a full-thickness tear, especiallylarger tears, tendon retraction may be present and thesupraspinatus may take on a more globular configuration(Fig. 99-36).229 The location of the musculotendinousjunction can vary even in asymptomatic individuals anddepends on the position of the arm during the MRexamination. Therefore, the use of retraction of themusculotendinous junction alone as a direct sign of arotator cuff tear in the absence of a clear tendondefect is not recommended. In large to massive tears thetendon may retract as far as the medial glenoid margin(Fig. 99-37).

MR arthrography is most helpful in distinguishingsmall from partial tears and tendinosis, and in assessingthe reparability of the cuff and the postoperativeprognosis in larger cuff tears. MR arthrography is helpfulin determining the size and location of cuff tears and inassessing the status of the torn tendon edges (Fig.99-38).The diagnosis of a full-thickness rotator cuff tear on MRarthrography is made when contrast extends through adefect in the tendon from the cuff undersurface into thesubacromial-subdeltoid bursa. The retracted tendonmargins may be thickened in response to healing orattenuated in more chronic tears. The uninvolved areasof tendon adjacent to the tear site may demonstratechanges of degeneration or partial-thickness tear. Thequality of the retracted tendon edges can be assessed onconventional MRI by assessing their appearance anddescribing them according to the classification schemediscussed earlier (good, fair or poor),187 and at MRarthrography by evaluating for the presence of contrastimbibition.23,32,57,230


F I G U R E 99-34

Subglenoid impingement. Axial oblique T1-weighted MR arthrogram withfat saturation performed with the patient in the abduction and externalrotation (ABER) position. Note the flaplike areas of undersurface partialtearing of the supraspinatus tendon (white arrow). There is fraying of theposterosuperior labrum (black arrow). Note the cystic areas of theposterosuperior humeral head (arrowheads).

F I G U R E 99-35

Insertional partial tear. Coronal oblique fast spin-echo proton-density–weighted image with fat saturation. A fluid-filled insertional defectis seen at the supraspinatus tendon insertion into the greater tuberosity(arrow).

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Secondary signs188,229 of rotator cuff tears are utilizedless commonly, with increased experience, and withbetter depiction of the primary tendon defects. Thesesecondary signs include diffuse loss of the peribursal fatplane and the presence of fluid in the subdeltoid bursa.Loss of the peribursal fat plane in association with arotator cuff tear is most likely related to the presence of

bursal fluid and/or inflammatory change, granulation orscar tissue.112,231 A large amount of fluid in the subdeltoidbursa is believed to represent extension of joint fluidthrough the capsule and tendon defect into the bursa. Ithas been considered a more specific finding of acomplete cuff tear, particularly if a large volume of liquidsignal is present.229 Nonetheless, smaller amounts of


A B

A B

F I G U R E 99-36

Moderate complete tear. A, Coronal oblique and B, sagittal oblique fast spin-echo T2-weighted images with fatsaturation. There is a complete tear of the supraspinatus tendon, retracted to the mid humeral head, involving thecentral to anterior aspect. There is degeneration of the medial tendon edges (arrows).

F I G U R E 99-37

Massive tear. A, Coronal oblique T2-weighted image. The supraspinatus tendon is retracted to the medial glenoidmargin (arrow). There is severe atrophy. B, Sagittal oblique T2-weighted image. Note the “bald humeral head.” Thetear extends from the subscapularis to the infraspinatus tendon (arrows).

099.qxd 17/6/05 12:56 PM 35

fluid in the subdeltoid bursa can be identified quitecommonly in patients without a tendon defect, espe-cially on fat-suppressed images, and may be indicative ofbursal inflammation (see Figs. 99-20, 99-27, and 99-28).Fluid in the subdeltoid bursa may also be seen in patientswith partial tears, especially those on the bursal surface.Although less common, large amounts of fluid in thesubdeltoid bursa may also be identified with primarysubdeltoid bursitis in patients with calcium hydroxy-apatite deposition disease (HADD) (see later) and otherinflammatory causes.96

Muscle atrophy is a secondary sign seen especially inassociation with large tears and chronic tears (Figs.99-37, 99-39, and 99-40).187,232-237 It is best identified on

T1- and proton-density–weighted images, particularly inthe sagittal oblique plane, and is not easily seen on fat-suppressed imaging sequences. Atrophy may, however,be seen in association with neurologic compromise,adhesive capsulitis, and other conditions in whichshoulder movement is restricted or absent, and thereforein and of itself is not diagnostic of tendon disruption.238-240

Other findings associated with large or chronicrotator cuff tears include a decrease in the acromial-humeral distance to less than 7 mm and the presence ofacromioclavicular joint cysts (Fig.99-41). The former canbe seen on plain radiographs as well, but if associatedwith a tear,MRI can be helpful to assess the extent of thedefect. Acromioclavicular joint cysts are associated withfull-thickness tears, usually large to massive, and occurwhen a high riding humeral head impacts on theoverlying acromioclavicular joint. This leads to wearon the inferior aspect of the acromioclavicular jointcapsule, with resultant tear. Fluid from the joint can thenextend through the tear and subdeltoid bursa, into theacromioclavicular joint. Removal of the cyst alone mustbe avoided because the condition tends to recur ifthe cuff tear is not repaired. The rotator cuff should berepaired and the cyst excised.241-243 Large joint effusionsmay also accompany rotator cuff tears. This is a non-specific finding. A recent study revealed the relationshipbetween intramuscular cysts of the rotator cuff and tearsof the rotator cuff244: intramuscular cysts of the rotatorcuff are associated with small, full-thickness tears orpartial undersurface tears of the rotator cuff (Fig. 99-42).These cysts are best identified on imaging sequenceswith T2-weighted contrast.

In more chronic tears a discrete tendon defect canbe more difficult to discern due to partial or completeobliteration of the tear due to scarring. Severe mor-phologic changes, a decrease in the acromial-humeraldistance, atrophy, and peribursal and bursal changes can


F I G U R E 99-38

Moderate size full-thickness tear. Coronal oblique T1-weighted MRarthrogram with fat saturation. High signal contrast outlines a defect in thesupraspinatus tendon. The tendon edges are mildly frayed (arrow).

A B

F I G U R E 99-39

Posterior extension of large full-thickness tear. A and B, Coronal oblique fast spin-echo inversion-recovery–weightedimages. The tendon defect is retracted to the medial one third of the humeral head (arrow in A). In B the posteriorextension of the tear into the infraspinatus tendon is seen (arrow). The retracted tendon edges are globular anddegenerated.

099.qxd 17/6/05 12:56 PM Page 3236

help in the recognition of these lesions on conventionalMR images.96 MR arthrography may be helpful in suchcases if doubt remains about the presence and extent ofsuch tears and surgery is contemplated.

MRI can also accurately determine the size of thetendon defects,187,188,245-247 including the amount ofmedial retraction, the anteroposterior extent of thedefect, as well as the overall cross-sectional area. Asnoted earlier the cross-sectional area of the tendondefect may be the most important factor in surgicalplanning. Sagittal and coronal oblique sequences canassess the medial and anteroposterior extent of cufftears. In conjunction with axial views they can alsodetermine the number of tendons involved, includingsupraspinatus, infraspinatus, and subscapularis tendons,as well as the location of the tendon defect (see Figs.99-39 and 99-40).

The site of rotator cuff tears can also be determinedwith MRI.82,177,179,187,188,234,248,249 Small full-thickness tearsare often found in the anterior portion of the distalsupraspinatus tendon, near its insertion into thegreater tuberosity at the junction with the biceps andsubscapularis tendon (near the rotator interval). They


A

C

B

F I G U R E 99-40

Anterior and posterior extension of large full-thicknesstear. A, Coronal oblique T2-weighted image. Thesupraspinatus tendon is retracted to the medial one thirdof the humeral head (arrow). The tendon edges are thin.There is moderate muscle atrophy. B, Coronal obliqueT2-weighted image, more posteriorly. The defectextends posteriorly to the infraspinatus tendon in a fluidfilled longitudinal cleavage plane (arrow). C, Axial T2-weighted image. The tendon lesion extends anteriorlyacross the rotator interval to involve the superodistalsubscapularis tendon (arrow).

F I G U R E 99-41

Acromioclavicular joint cyst. Coronal oblique fast spin-echo T2-weightedimage. A large acromioclavicular joint cyst is seen (long arrow), associatedwith a retracted full-thickness rotator cuff tear (short arrow).

099.qxd 17/6/05 12:56 PM Page 3237

are therefore best seen on far anterior coronal obliqueimages or on lateral sagittal oblique images (Fig. 99-43).Partial-thickness tears show a predilection for this areaas well. When larger, the tears extend to involve theinfraspinatus tendon from anterior to posterior aspect(see Figs.99-37,99-39,and 99-40). The component of thetear involving the infraspinatus is seen on the moreposterior coronal oblique images or on sagittal obliqueimages. Anterior tears and larger tears may extend toinvolve the rotator interval capsule and the subscapularistendon and there may be an associated lesion of thebiceps tendon (Figs.99-40 and 99-44). The biceps tendon

is often implicated in these situations since it liesbeneath the anterior aspect of the supraspinatus tendon,which then subjects it to even further impingementbetween the humeral head and acromion when thesupraspinatus tendon is torn. Subscapularis and infra-spinatus tears may also be visualized in the sagittaloblique and axial plane images in addition to the coronaloblique plane where the supraspinatus tendon defectsare best seen. In larger tears and anterior tears of thesupraspinatus tendon, axial images superior to theglenohumeral joint may also demonstrate the fluid-filledtendinous gap.


A B

A B

F I G U R E 99-42

Intramuscular cyst. A and B, Coronal oblique STIR images. Note the full-thickness tear in A (arrow) and theassociated intramuscular cyst in B (arrow).

F I G U R E 99-43

Small complete tear. A, Coronal oblique and B, sagittal oblique fast spin-echo T2-weighted images with fatsaturation. Note the small rotator cuff tear outlined by fluid signal (arrows). Small tears tend to begin and occur at theanterior distal supraspinatus tendon near its insertion.

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The presence of muscle atrophy187,232,234-237,250,251 is, asnoted earlier, a secondary sign associated with a rotatorcuff tear, and the degree and presence of muscle atrophyis highly correlative with the size of the tear. Muscleatrophy has importance in determining surgical out-come with regard to return of muscle strength. Atrophyis identified as a decrease in muscle bulk and size. Therewill be an increase in fat signal within the muscle belly,

often appearing as linear bands of high signal on T1-and proton-density–weighted images, though otherpatterns may be seen (Fig.99-45). This may be separatelydescribed as fatty infiltration (degeneration).190,235,251

Images with fat suppression only are less helpful inevaluating muscle atrophy except for visualization of adecrease in muscle bulk. The degree of muscle atrophyand fatty infiltration is most commonly graded as mild,


A B

A B

F I G U R E 99-44

Rotator interval anterior tear. Biceps lesion. A, Coronal oblique fast spin-echo T2-weighted image with fat saturation.Note the tear in the anterior supraspinatus tendon. The torn tendon fibers are markedly thickened and showdegeneration of the edges (arrow). B, Axial fast spin-echo T2-weighted image with fat saturation. The tear extendsanteriorly, likely disrupting the rotator interval, and the superodistal aspect of the subscapularis tendon, leading toinstability of the proximal aspect of the long head of the biceps tendon which migrates medially (“hidden lesion”)(arrow).

F I G U R E 99-45

Muscle atrophy. A, Coronal oblique proton-density–weighted image. Note the retracted supraspinatus (black arrow).The supraspinatus muscle reveals muscle atrophy manifested by a decrease in bulk and infiltration by fat (white arrow).B, Sagittal oblique T1-weighted image. Note the presence of atrophy in both the supraspinatus and infraspinatusmuscle bellies (arrows).

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moderate, and severe. Thomazeau et al237 developed aratio using an image in the oblique sagittal plane whichcrosses the scapula through the medial border of thecoracoid process. They stated that this view allowed areliable measurement of supraspinatus muscle atrophyby the calculation of an occupation ratio (R), which wasthe ratio between the surface area of the cross-section ofthe muscle belly and that of the supraspinous fossa.Zanetti et al236 described the use of standardized cross-sectional areas for quantitative assessment of the musclebulk of the rotator cuff with MRI. Standardized cross-sectional areas were determined by the rotator cuffmuscle area divided by the area of the supraspinatusfossa. They also described a tangent sign which is basedon their assumption that a healthy supraspinatus musclecrosses a line (tangent) drawn through the superiorborders of the scapular spine and the superior marginof the coracoid. Sagittal T1-weighted turbo spin-echoimages of the shoulder were utilized. Goutallieret al189,190 graded the degree of muscle atrophy and fattyinfiltration into five grades of fatty degeneration of therotator cuff muscles.

Assessment of the status of the torn tendon edges isalso important for the operating surgeon in preoperativeevaluation. MRI and MR arthrography can be used toassess the appearance of the torn tendon edges andto indicate whether they are of good quality, or arefrayed or fragmented and of poor quality (see Figs.99-38,99-39, 99-40, and 99-44), or imbibe contrast and aredegenerated as determined by MR arthrography (seeFig. 99-38).57,187,188,247

Diagnostic Performance

The diagnostic performance of MRI in rotator cuffdisease has been studied.8,96,187,188,217,218,220,227,228 Moststudies have found a high sensitivity, specificity, andaccuracy in the region of 90% to 95%. For partial-thickness tears the sensitivity is decreased and morevariable but the majority of studies have determined adiagnostic performance in the region of 85%. Improveddiagnostic performance is seen with fat-suppressiontechniques.

Other investigators have tested the diagnostic per-formance of fast spin-echo techniques in the evaluationof rotator cuff tears and have found them to be similarlyefficacious. Performance is better with fat suppression,especially in the diagnosis of partial tears.2,3,6,252

Recently the assessment of the rotator cuff with lowfield extremity magnets has come into increased usage.Results using these techniques with experiencedmusculoskeletal radiologists approach those with higherfield systems.210,221

MR arthrography can improve the diagnosticperformance and confidence in the evaluation of rotatorcuff tears19,26,32,35,39,57,180,253 over conventional T2-weighted MRI, particularly in the evaluation of partial-thickness tears of the undersurface. It is not useful in theassessment of partial-thickness tears confined to thebursal side of the cuff or intrasubstance tears unlesspost-contrast images with T2 weighting are employed.The use of the ABER position may improve the

diagnostic performance of MR arthrography in certainclinical circumstances as well.39 The sensitivity andspecificity of MR arthrography in the evaluation ofcomplete tears approaches 100%.29 The diagnosticperformance of MR arthrography is improved with theuse of fat suppression.32,34 Fat suppression helps inconfirming that the high signal above the tendon inthe subacromial-subdeltoid bursa region is contrast andnot fat in the peribursal fat plane. Fat suppression alsoimproves the diagnostic accuracy of detecting smallpartial tears of the undersurface.32,34 The diagnosticperformance of indirect MR arthrography45,47,254 revealscomparable sensitivities and specificities for rotatorcuff pathology.

Tears of the Subscapularis Tendon

Involvement of the subscapularis tendon is relativelyuncommon but is being recognized more frequentlywith better understanding of the causes of injury andimproved imaging techniques. Tears of the subscapularisare recognized in 8% of patients in association with tearsof other components of the rotator cuff.167

Injury to the subscapularis may also occur with largertears of the rotator cuff as well as anterior tears (see Figs.99-40 and 99-44). Incomplete tears of the subscapularistendon may also occur in conjunction with small ormedium-sized tears of the supraspinatus tendon. In astudy of 46 cadaver shoulders,255 20 shoulders had a tearof the supraspinatus tendon and 17 had a tear of thesubscapularis tendon. The majority were articular-sideincomplete tears on the upper portion. Lesions of thelong head of the biceps brachii were identified in 14(30.4%) shoulders. On MRI these articular-side partialtears were identified as an area of high signal intensity onaxial T2-weighted images.

Degeneration and tearing of the subscapularis (aswell as the rotator interval capsule) may also occur inpatients with subcoracoid impingement.256-260 Sub-coracoid impingement leads to subscapularis tendonimpingement pathology, visible on MR examination,similar to that described with the stages of supraspinatusimpingement (see Fig. 99-46). Thickening and fluid mayalso be present in the subcoracoid bursa.259 Fluid in thesubcoracoid space, revealed on MRI of the shoulder, maylie in the subcoracoid bursa or the subscapularis recess.Subcoracoid effusions may also be associated withanterior rotator cuff tears, including tears of the rotatorinterval.261

Isolated injury of the subscapularis is uncommon.Acute isolated ruptures of the subscapularis can occurwith severe trauma. Traumatic injury of the subscapu-laris is caused either by forceful hyperextension orexternal rotation of the adducted arm. Such injury mayalso occur in elderly patients with recurrent anteriordislocation.163,164,167,168,178,262,263

On MRI examination the spectrum of pathology inthe subscapularis may range from advanced thickeningand increased signal on images with T1- and proton-density–weighted contrast, reflective of tendinosis, topartial-thickness tears in the substance and in thesuperior distal insertion (Fig. 99-46). Full-thickness


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tendon tears are associated with fluid signal on imageswith T2-weighted contrast and with medial tendonretraction (Fig. 99-47). Less commonly, fluid may extendinto the subdeltoid bursa. Use of both the sagittaland axial images aid in the assessment of tears of thesubscapularis tendon.75,167,179,181

Subscapularis tendon rupture may be associated withdisruption of the stabilizers of the biceps, such as thetransverse humeral ligament, as well as the coraco-humeral ligament within the rotator interval. This maythen result in medial subluxation or dislocation of thebiceps tendon,264,265 and is best seen on axial images(see Fig. 99-46).

Infraspinatus and Teres Minor injuries

Most tears of the infraspinatus tendon occur inassociation with large tears of the supraspinatus tendonor with injury to the teres minor tendon in posteriordislocation.184,266 Isolated injury of the infraspinatustendon is not that common. It may occur in youngerpatients who subject this area to stress in overheadmotion or as part of the posterosuperior subglenoidimpingement syndrome.143 Full-thickness tendon defectsmay be seen in all three imaging planes and the criteriaare similar to those for tears of the supraspinatus tendon,with the lesion appearing as a fluid-filled defect onimages with T2-weighted contrast (see Fig. 99-48).

Injuries of the teres minor without other rotator cuffinjury may be identified with MRI and MR arthrog-raphy,184 but are not common. They may occur afterposterior dislocation in association with posteriorcapsular tears. Injuries may range from muscle edema topartial and complete tendon tears. Tendon tears aremanifested by tendon discontinuity on MRI exami-

nation. The tendon may be avulsed from its insertioninto the greater tuberosity. MR arthrography may alsoreveal extravasation of contrast material behind theshoulder joint.184

Rotator Interval Lesions

Rotator interval tears are a clinically important subtypeof rotator cuff tear. Tears of this region may be difficultto diagnose with MRI. Differentiation of a true rotatorinterval tear from normal synovium and capsule in thisspace may often not be possible with MRI and symptomsmay be referred and misleading.76,267


CP

A B

F I G U R E 99-46

Subscapularis lesions. A, Axial fast spin-echo T2-weighted image with fat saturation. The subscapularis tendon isthickened and there is increased signal in its substance, findings which are reflective of tendinosis (arrow). B, Axial fastspin-echo T2-weighted image with fat saturation. In addition to thickening and increased signal, note the focus oflinear fluid signal in the substance of the subscapularis tendon, reflective of an intrasubstance partial tear (white arrow).Note the cyst in the lesser tuberosity (black arrow) and the narrow subcoracoid space, reflective of subcoracoidimpingement. CP, coronoid process.

F I G U R E 99-47

Subscapularis tear. Biceps dislocation. Axial short tau inversion recovery(STIR) image. Note the retracted torn subscapularis tendon (white arrow)with medial dislocation of the long head of the biceps tendon (black arrow).

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The rotator interval is defined as the space betweenthe superior border of the subscapularis muscle andtendon below and the supraspinatus muscle and ten-don above77,78,268 (Fig. 99-11). It is a complex regionand can be conceptualized in layers.68,269 The outer-most layer consists of fibrofatty tissue and beneath thisis the coracohumeral ligament, the joint capsule, andthen the superior glenohumeral ligament. The deepeststructure in the anterior interval is the long head of thebiceps tendon.Surgeons may enter the joint through thisregion for an arthrotomy. It is through this interval thatthe long head of the biceps tendon enters the shoulderjoint from the proximal bicipital groove to extend tothe superior labral-biceps anchor and the supraglenoidtubercle attachment. The interval is bridged by the rotatorinterval capsule.270 The fused rotator interval capsuleand the coracohumeral ligament may be seen as a roofover the biceps tendon, and are important anteriorsupporting structures for shoulder function.

It is believed that injury or deficiency of the rotatorinterval capsule and coracohumeral ligament may lead toposterior inferior laxity and instability.270 Lesions of therotator interval may also be seen in association withshoulder subluxations and dislocations,where this regionmay be an area of relative weakness susceptible to injuryand therefore during which time this region may be tornor enlarged. As such many surgeons believe this areashould be repaired or reinforced during stabilizationprocedures for instability.

Injuries to this interval may also occur in individualswithout a history of instability.268 In this circumstancethere may be an anterior tear of the supraspinatustendon as well as a tear of the superior subscapularistendon, in association with the tear of the interval.Isolated lesions of the rotator interval appear thin andlongitudinal, and are not associated with muscle

retraction.267 Tears of the rotator interval may causecommunication with the subdeltoid bursa, and fluid orcontrast may be seen in this region on conventional MRIand MR arthrography. This may be identified along withaltered signal in the region of the interval involvingstructures such as the coracohumeral ligament and thelong head of the biceps tendon, without necessarilyinvolving the supraspinatus tendon. This may beconfusing if this anatomy and lesion are not understood.Lesions of the rotator interval may often be best dis-cerned on sagittal oblique T2-weighted imaging sequenceswith fat suppression, or with MR arthrography.

The structures that contribute to the functionalanatomy of this region, or may be injured in associationwith them, include the anterior margin of thesupraspinatus tendon, distal superior margin of thesubscapularis tendon, coracohumeral ligament, rotatorinterval capsule, superior glenohumeral ligament, andlong head of the biceps tendon. Injuries to the superiorlabrum and biceps labral anchor may also occur, as wellas the ligamentous reflection pulley for the long head ofthe biceps tendon formed by these structures at thelateral margin of the rotator interval, extending to thelesser tuberosity and proximal bicipital groove. It alsoincludes the transverse humeral ligament.

The lesions may be acute as after a dislocation, orchronic as in overuse injuries. If acute, the alterationsmay be identified as areas of edema, fluid signal, andsynovitis, and have high signal on T2-weighted images, orif chronic, show areas of thickening and scarring,revealed as areas of low-to-intermediate signal in theregion of the interval, including the coracohumeral liga-ment and capsule (Fig. 99-49). Other associated injuriesmay occur to the biceps tendon, including inflamma-tion and tear, or with disruption of the transversehumeral ligament, or tear of the subscapularis tendon at


A B

F I G U R E 99-48

Infraspinatus tear. A, Coronal and B, sagittal fast spin-echo T2-weighted images with fat saturation. Note the isolatedtear of the infraspinatus tendon (arrows).

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its attachment to the lesser tuberosity, biceps instabilityincluding medial dislocation. With interval disruptiontearing of the distal anterior supraspinatus tendon at itsinsertion into the greater tuberosity, “the anterior orleading edge”at the lateral rotator interval may also occur.Owing to the course of the long head of the bicepsthrough the interval to the superior labrum,SLAP lesionsmay also occur.76

These lesions are often better recognized on sagittaloblique sections or axial sections, acquired as eitherT2-weighted fast spin-echo imaging with fat suppressionor with MR arthrography.When any one of the spectrumof these associated injuries is suspected or found allother possible associated injuries should be searched foron MR examination.76

Rotator Cuff Tear Arthropathy

Rotator cuff tear arthropathy186,271,272 occurs in thesetting of large-to-massive tears (Fig. 99-50). In additionto the presence of the advanced disruption of the cuffthere is abrasion of the humeral head articular cartilageagainst the coracoacromial arch, causing subacromialimpingement that in time erodes the anterior portion ofthe acromion and the acromioclavicular joint. Theremay be collapse of the soft, atrophic humeral head,186

with eventual erosion of the glenoid and coracoid.While many of these findings may be visible on plainradiographs,185 MRI can help assess the full extent ofbone and soft-tissue involvement. This process shouldbe recognized and described at the time of MRIevaluation, as the best treatment for this may be totalshoulder replacement, if possible with rotator-cuffreconstruction.186

Biceps Tendon

The biceps tendon may also become involved in patientswith impingement and rotator cuff tears.79,89,223,273-281 Ingeneral the extent of disease in the biceps is less severethan that in the cuff, but follows the progression seen inthe rotator cuff. A small amount of fluid may be observedin the biceps tendon sheath even in asymptomaticindividuals.111 Since the tendon sheath communicateswith the joint it may fill with fluid when a shoulder jointeffusion is present from some other cause; therefore, thisis a nonspecific finding. Tenosynovitis can be diagnosedwhen the amount of fluid in the tendon sheath is out ofproportion to that in the joint.

Tendinosis of the biceps tendon may manifest by anincrease in tendon size and increased signal in itssubstance on T1- and proton-density–weighted images(Fig. 99-51). With T2-weighted fast spin-echo imagingwith fat suppression or fast spin-echo STIR the increasedsignal may persist or mildly increase.

In shoulders with tears of the rotator cuff the bicepsalso becomes an active depressor of the head of thehumerus.282 On MRI examination the biceps may enlargeas a response to this increased workload. This issometimes termed “tendonization.”

Partial-thickness tears may be more easily discernedwhen there is alteration in morphology, such as thinning,irregularity, or splitting of the tendon. Biceps tendonruptures may be seen with anterior tears of the rotatorcuff (Fig. 99-52). Up to 7% of large rotator cuff tears arealso accompanied by biceps tendon rupture. After a tear,the intracapsular portion of the tendon lies free in thejoint cavity while the extra-articular portion is pulleddistally.With MRI the tendon is absent from the groovewhich is filled with fluid. Distal retraction of the muscle


F I G U R E 99-49

Rotator interval injury. Coronal oblique T2-weighted fast spin-echosequences with fat saturation. Fluid signal due to edema and synovitis, aswell as areas of thickening and scarring, revealed as areas of low-to-intermediate signal in the region of the rotator interval, are noted (arrows).Fluid is also present in the anterior aspect of the subdeltoid bursa.

F I G U R E 99-50

Rotator cuff arthropathy. Coronal oblique fast spin-echo T2-weightedimage with fat saturation. There is a large retracted full-thickness tear(black arrow). Changes of rotator cuff arthropathy are seen. Note thedecrease in the acromiohumeral distance, the scalloping and resorption ofthe undersurface of the anterior acromion (arrowhead), and the fraying andthinning of the articular cartilage of the humeral head, along with cysticchange (white arrow).

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and tendon may be seen, best identified in longitudinalplanes of section. Occasionally the intertuberculargroove may fill with scar tissue of low signal and maylead to a false-negative diagnosis.

Medial dislocation of the biceps tendon may alsoresult from chronic impingement, associated with a largeanterior cuff tear.13,179,273,277-279 There is tearing of thesecondary biceps stabilizers, including the anteriorsupraspinatus and subscapularis tendons, and thecoracohumeral ligament. The low signal tendon isdisplaced medially outside the intertubercular groove(see Figs. 99-44 and 99-47). This is best seen on axial

views. There may be an extra-articular tendon disloca-tion with an intact subscapularis. With rupture of thesubscapularis tendon either post trauma or with a largeor massive cuff tear the biceps tendon may also dislocateintra-articularly. The biceps tendon may then extend intoand be entrapped in the joint.

Calcium Hydroxyapatite Deposition Disease

The shoulder is the most common site of involvementwith calcium hydroxyapatite crystal deposition disease(HADD). Patients may often be asymptomatic, butclinical symptoms occur in 30% to 45% of patients inwhom calcifications are present. The disorder occurs inboth males and females, usually between the ages of 40and 70 years. The pathogenesis of hydroxyapatite crystaldeposition is unknown, though trauma, ischemia, orother systemic factors may induce abnormalities in theconnective tissue, leading to crystal deposition.283-285

Crystal deposition most commonly occurs in thetendinous and bursal structures about the shoulder,particularly the supraspinatus tendon (see Fig. 99-53)(52%). It may become bilateral in up to 50% ofpatients.283 In the supraspinatus tendon it may target thecritical zone, as this may be an area of both alteredvascularity and mechanical pressure, which thereforemay predispose it to hydroxyapatite crystal deposition.It may also occur in the other tendons of the rotatorcuff, or in the biceps tendon. Bursal calcification is mostcommon in the subacromial-subdeltoid bursa. Thesecrystals incite a synovitis, tendinitis or bursitis andperiarticular inflammation. The calcification alone maynot be the inciting agent, but symptoms may occur withthe dissolution of the calcium.With rupture of a calcificdeposit, hydroxyapatite crystals are spilled into thesurrounding soft-tissue space or bursa, setting off an


F I G U R E 99-51

Biceps tendinosis. Sagittal oblique T2-weighted image with fat saturation.Note the high-grade partial tear in the supraspinatus tendon (long arrow).The biceps tendon is thickened and shows increased signal in its substancereflective of tendinosis (short arrows).

A B

F I G U R E 99-52

Biceps tendon rupture. A, Coronal oblique and B, axial T2-weighted images with fat saturation reveal the tornrotator cuff involving the supraspinatus tendon in A and subscapularis tendon in B (arrows). The biceps tendon is rup-tured and retracted to the region just below the humeral neck (arrowheads). Note the empty, fluid-filled groove in B.

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acute inflammatory response. Milwaukee shoulder con-sists of a destructive arthropathy,hydroxyapatite deposits,high collagenase activity in the synovial fluid, and rotatorcuff tears.271,286

The nodular calcific deposits in HADD can usually beeasily seen with plain radiographs and the combinationof radiographs and the characteristic history is usuallysufficient for diagnosis and subsequent therapy. WhenMRI is obtained in these patients the calcific densities,usually of low signal intensity, may be difficult to see,especially when small, due to the lack of contrast withthe low signal of the tendons (Fig. 99-53). They aredifficult to differentiate from a thickened tendonwithout calcification.287 It may be difficult to distinguisha calcified tendon from a thickened tendon withoutcalcification. They may be more easily identified whenthey are large, or if there is subjacent high signal onimages with T2-type contrast, related to peritendinousedema and inflammation. T2*–gradient-echo images mayalso enhance visualization by providing a bloomingeffect. Although areas of high signal intensity may beobserved about foci of calcification in tendons andbursae on T2-weighted spin-echo MR images and afterinjection of gadolinium intravenously, the correlation ofsuch findings to calcific tendinitis and bursitis has notbeen proved.191,288

When the calcifications are seen, MRI can localize thespecific tendons or bursa involved and documentassociated changes such as tendinitis,or the less commontears. Tears of the rotator cuff can occur in associationwith calcific tendonitis, though the mechanism is not yetclear.289 It may relate to localized hyperemia in thetendon, which may lead to impingement.

The presence of effusions in the subacromial-sub-deltoid bursa can be identified, particularly afterextrusion of the calcifications into the bursa. MRI mayalso be helpful in these patients to exclude other causesof shoulder pain. In patients with Milwaukee shoulderthe extent of joint destruction may be determined andthe presence of a rotator cuff tear, as well as its extent,can be documented.

Bone Injuries

Nondisplaced fractures and bone contusions about thehumeral head (Fig. 99-54) and greater tuberosity mayresult in pain and associated contusion-like injuries ofthe rotator cuff that may mimic pain due to rotator cufftears. Anzilloti et al213 found that this tended to occurin younger patients and in atypical locations of thesupraspinatus tendon. This post-traumatic strain of therotator cuff was typically associated with a bone bruisein this study.213

SHOULDER INSTABILITY

General Features

The shoulder is considered the most unstable joint in thehuman body. A simple definition of instability indicatesthat the humeral head slips out of its socket duringactivities. In the past it was considered to be present onlyif a previous dislocation had occurred. Now more subtledegrees of instability are well recognized, including


A B

F I G U R E 99-53

Calcium hydroxyapatite crystal deposition disease (HADD). A, Coronal and B, sagittal oblique fast spin-echoT2-weighted images with fat saturation. There is a nodular focus of low signal consistent with calcium in the centralaspect of the supraspinatus tendon (arrows). Fluid is also seen in the subdeltoid bursa (arrowhead).

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subluxation and instability that results from micro-trauma.70,290 Although the humeral head may translate asmall amount during daily activities, these more subtletypes of instability may result in pain from spasm orcapsular stretching. The traditional forms of instabilityshould be differentiated from glenohumeral joint laxity,in which asymptomatic passive translation of the humeralhead on the glenoid fossa is observed. Glenohumeraljoint laxity and instability may however coexist.

Instability may be classified according to frequency(acute, recurrent, or chronic), degree (subluxation ordislocation), etiology, and direction.291,292 With regardto etiology, instability may result from one specifictraumatic episode (termed traumatic instability), fromrepetitive microtrauma in activities such as swimming orthrowing, or without any history of trauma (termedatraumatic instability). In the latter cases there is oftena coexistent history of congenital ligamentous laxity.Shoulder instability can also be described by directionas anterior, posterior, or inferior to the glenoid, ormultidirectional.291,292 Anterior instability is by far themost common type of instability. Functional instability isanother term used to describe instability and it indicatesthat derangement of the shoulder is caused by damagethat may be confined to the glenoid labrum.293,294 Theshoulder may catch, slip, or lock and may not exhibitsubluxation or dislocation. Another term in current useto define different types of minor instability is micro-instability. This is said to occur in some 5% of patients. Itis a spectrum of disorders involving the upper half of theshoulder joint, as opposed to more traditional instabilitywhich involves the lower third to half. Involved in theetiology of this process are entities such as a lax rotatorinterval and there may also be a history of overuse inthese patients.295,296

Anterior Instability

Clinical Features

Recurrent subluxation or dislocation (shoulder insta-bility) is the most frequent complication of acutetraumatic dislocation. When the initial event occursbetween the ages of 15 and 35 years the dislocationsusually become recurrent or habitual. Once a seconddislocation has occurred the patient becomes a “recur-rent dislocator.” The recurrence rate in the younger agegroup of patients is very high and may be as high as 80%to 90%.297,298 Recurrences usually occur in the first2 years. The damage to the shoulder seems to occur atthe time of the original trauma, though each redisloca-tion may cause further damage. The incidence ofrecurrence seems to be inversely related to the severityof the initial trauma.293,299-301 There does not appear tobe a relationship between the length and type of immo-bilization and the development of redislocation,293,294,302-304

though many surgeons still immobilize the shoulders ofyounger patients for up 6 weeks in the hope of allowingthe damaged tissues to heal. Recurrences are morecommon in men.

Over the age of 40 years the recurrence rate typicallydrops to 15% or less.166 In older patients the spectrum oflesions is different and there is more often a tear of therotator cuff or fracture of the greater tuberosity.

Pathologic Lesions

Patients with recurrent subluxations and dislocationsincur lesions to the capsular mechanism. The essentiallesion of instability described by Bankart is detachmentof the glenoid labrum and capsule from the anteriorglenoid margin.305 Others believe the most importantabnormality is a Hill Sachs defect.306-309 Fractures of theinferior glenoid margin, insufficiency, stretching, oravulsion of the subscapularis muscle and tendon, andstretching rather than actual detachment of the anteriorcapsule may also be important. Other factors includeaplasia or hypoplasia of the glenoid,variations in contourof the glenoid fossa, excessive anteversion of theglenoid, increased anteversion of the humeral head, andmuscle imbalances.54,310

True Bankart lesions are more commonly found inpatients with a history of complete traumatic disloca-tion. In patient with a history of a subluxating shoulderthere may just be laxity or redundancy of the capsule,though labral lesions, fractures of the glenoid rim, andarticular defects of the posterolateral humeral head mayalso be seen. Damage to the glenoid rim and Hill-Sachslesions are more frequently found in complete traumaticdislocation.310-314

Bone Abnormalities

The two most common bone abnormalities are Hill-Sachs lesions and fractures of the inferior glenoidmargin. A Hill-Sachs lesion is a specific indicator of aprior anterior glenohumeral joint dislocation. It is aposterolateral notch defect in the humeral head that is


F I G U R E 99-54

Greater tuberosity contusion. Coronal inversion-recovery–weightedimage reveals a greater tuberosity contusion (long arrow). Also note thereis mildly increased signal in the supraspinatus tendon which could reflectpost-traumatic strain or contusion (short arrow). The small amount of fluidin the subdeltoid bursa may indicate some post-traumatic bursitis(arrowhead).

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created by impingement of the articular surface ofthis portion of the humerus against the anteroinferiorrim of the glenoid fossa. It is most common in patientswith recurrent anterior subluxation and dislocation,315

and uncommon in patients with anterior subluxa-tion alone,292 multidirectional instability, or labral pathol-ogy not associated with recurrent subluxations ordislocations.

On MRI, Hill-Sachs lesions appear as wedgelikedefects on the posterolateral aspect of the humeral head(Fig. 99-55). They are identified above the level of thecoracoid process.315-318 They are best seen on axialimages, but may also be apparent on coronal and sagittaloblique images (Fig. 99-56). Both the larger, moretraditional Hill-Sachs lesions and the minor impactioninjuries of the humeral articular cartilage and subchon-dral plates that may be more easily appreciated witharthroscopy can be seen.Hill-Sachs lesions should not beconfused with the normal posterolateral flattening seenin the inferior aspect of the humeral head and which istypically present below the level of the coracoid.318

Depending on their age, Hill-Sachs lesions may be asso-ciated with marrow edema (see Fig. 99-56) or trabecularsclerosis. MRI imaging was found to have a sensitivity of97%, a specificity of 91%, and an accuracy of 94% in thedetection of a Hill-Sachs lesion.315

The osseous Bankart lesion (Figs.99-57 and 99-58) is adefect in the anterior inferior margin of the glenoidrim.319 Cross-sectional imaging with either CT or MRIwith or without intra-articular contrast injection can behelpful in depicting these lesions273,320-322 and determin-ing their size and location. It is generally thought that alarge defect should be treated with bone-grafting, butthere is a lack of consensus with regard to how large adefect must be in order to necessitate this procedure.Some investigators have proposed that a defect must

involve at least one third of the glenoid surface in orderto necessitate bone grafting.319,323 When large, bonyBankart lesions may lead to reversal of the normal pearshape of the glenoid surface, a situation that promotesrecurrent dislocations. The bony glenoid rim lesions maybe easier to interpret with CT, especially fractures andectopic ossification, although lesions in the subchondralbone and marrow are more easily identified with MRI.On MRI cystic change and sclerosis may be seen. STIRimages and/or intermediate or T2-weighted MRI imageswith fat suppression in the sagittal oblique plane maydepict particularly well bone and marrow alterations


F I G U R E 99-55

Hill-Sachs lesions. Axial T1-weighted image (TR/TE 800/17 ms) at the levelof the coracoid process. A wedge-like defect is seen at the posteriorsuperior lateral aspect of the humeral head (arrows).

F I G U R E 99-56

Hill-Sachs lesion. Coronal oblique fast spin-echo T2-weighted image(TR/TE 3916/54 ms) with fat suppression. A Hill-Sachs lesion with asso-ciated marrow edema is seen along the posterior superior aspect of thehumeral head (arrow).

F I G U R E 99-57

Bony glenoid margin lesions (“bony Bankart”). Axial proton-density–weighted image. A large fracture fragment from the mid to anterior inferiorglenoid is seen in this patient after anterior dislocation (arrows).

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associated with Bankart lesions (Fig. 99-58). CT withreformatted images with 3D reconstruction may aid indetermining the size of the defect and the need for bonegrafting to prevent recurrence after surgery.323-325

Labral, Capsular, and Ligamentous Lesions

General Features

The soft-tissue lesions associated with recurrent anteriorsubluxation and dislocation include damage to theanterior glenoid labrum, associated glenohumeralligaments (labroligamentous complex), and anteriorcapsule.292,293,305,326-329 Specifically the “cartilaginous”lesion as originally described by Bankart has beenconsidered to be an avulsion or tear of the glenoidlabrum and/or stripping of the joint capsule. The damageto the anterior labrum that is seen at surgery, however,may vary from detachment of the labrum from theglenoid rim, to tears of the substance of the labrum, to acompletely destroyed or absent labrum.293

Injury to the labroligamentous complex typically willinvolve the region of the anterior band of the inferiorglenohumeral ligament. Failure of this complex mayoccur at its glenoid insertion site (70-75% of cases). Thelabrum tears as it is avulsed by the glenohumeralligaments at the time of injury. Failure of this complexmay also occur at its humeral insertion site (5-10% ofcases), or in its substance (15-20%), whereby there willbe capsular failure due to tear or laxity. Those associatedwith glenoid-sided failure include the Bankart lesiondescribed earlier and its less common variants, thePerthes lesion and the anterior labroligamentous peri-

osteal sleeve avulsion (ALPSA) lesion. Lesions associatedwith humeral failure include humeral avulsion of theglenohumeral ligament (HAGL) and its bone counterpart(BHAGL) lesion. Failure of this ligament at both itsglenoid and humeral insertion destabilizes both ends ofthe anterior band of the inferior glenohumeral ligament[floating avulsion of the inferior glenohumeral liga-ment (AIGHL)].

A typical Bankart lesion would be an avulsion of thelabroligamentous complex from the anteroinferiorportion of the glenoid.329-331 The periosteum of thescapula is lifted and disrupted. It occurs at the 3 to6 o’clock position, but may extend upward. The soft-tissue lesion may be avulsed together with a piece ofbone, the “bony” Bankart lesion, along the anteroinferioraspect of the glenoid rim.307

Labral Lesions

The labrum has been divided into six quadrants:I, superior; II, anterior superior; III, anterior inferior;IV, inferior;V,posterior inferior;and VI,posterior superior.Lesions of the glenoid labrum are considered to be areliable sign of instability. Normal variation occurs in thesuperior and anterior superior portion from the 11 to3 o’clock position, including the sublabral foramen andthe Buford complex. Pathology in the labrum associatedwith anterior instability typically occurs in the anteriorinferior portion from the 3 to 6 o’clock position. Inter-mediate signal occurs in the sublabral zone between thearticular cartilage of the glenoid.105 Another cause ofdifficulty is the occurrence of magic angle phenomenonin the labrum on short TE sequences.

The criteria used to diagnose an abnormality ofthe glenoid labrum include alterations in its mor-phology and/or signal intensity. Increased signal withinthe labrum not extending to the surface reflectsinternal labral degeneration.187 A torn labrum has mod-erate or intense signal on short TR/TE, density-weightedor gradient-echo images, extending to the surface ofthe labrum, and brightens on T2-weighted or fat-suppressed proton-density images (Fig. 99-59A) orimbibes contrast into the defect at MR arthrography(Fig. 99-59B).105,187,273,332-334 Abnormal labra may alsobe blunted, eroded, or frayed and irregular.

The diagnostic performance of MRI and MRarthrography in the evaluation of labral tears has beenevaluated. One study of conventional MRI found asensitivity of 93% and a specificity 87%.187 A larger studyfound a sensitivity of 89% and a specificity of 97%.5

MRI was found to be most sensitive in the evalua-tion of anterior labral tears and least sensitive insuperior and posterior tears. MRI arthrography revealsa diagnostic performance similar to or better than con-ventional MRI and better reveals labral separation/detachment.33,56,273,335-338

Capsular Lesions

In patients with shoulder instability after one orrepeated dislocations and or subluxations there maybe traumatic avulsion of the capsule from its glenoid


F I G U R E 99-58

Bony glenoid margin lesions (“bony Bankart”). Sagittal oblique T2-weightedfast spin-echo image with fat suppression. A bone defect with marrowedema of the anterior more inferior glenoid (large arrow) parallels thelabroligamentous avulsion. Note the anteriorly displaced, low signal bonefragment (small arrow).

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insertion. In the latter circumstance the capsule wouldbe peeled back to the neck of the scapula with the firstand subsequent dislocation. This is described as capsularstripping or shearing.

The anterior inferior capsule and associatedglenohumeral ligaments (especially the anterior band ofthe inferior glenohumeral ligament) can often best beseen on arthrographic MR examination on fast spin-echoproton-density, intermediate,or T2-weighted images withfat suppression, or with T2*-weighted 2D gradient-echotechniques, particularly when there is a significanteffusion. In the absence of an effusion MR arthrographyis very useful, especially to clearly identify the anteriorinferior labrum and inferior glenohumeral ligament.Withinjury to this region fluid or contrast may also be seen toextend beneath the soft tissue mantle. In a typicalBankart lesion the labrum will be torn or detached withthe capsular structures and fluid signal or contrast mayextend within or beneath the labrum as well (Figs.99-60,99-61, and 99-62). The assessment of the capsule shouldbe at the midglenoid or below, since on the moresuperior images a distended subscapularis bursa ormedial capsular insertion may mimic capsular strip-ping.339 Evaluation of capsular stripping may then betterreflect disruption of the anterior inferior labralligamentous complex.223,340

Bankart Lesion Variants

The earlier discussion focuses on the typical lesion ofanterior instability—the Bankart lesion, which is anavulsion of the anterior inferior labrum, capsule, andinferior glenohumeral ligament complex, with anassociated disruption of the scapular periosteum (seeFig. 60-62). There are however a number of variants ofthis typical lesion.

Perthes Lesion

This lesion341 is a labral ligamentous avulsion in whichthe scapular periosteum remains intact but is strippedmedially. The periosteum may then become redundant,and recurrent instability may occur as the humeral headmoves forward into this region of acquired laxity(pseudojoint). The labrum may then lay back down intoa relatively normal position on the glenoid andresynovialize (heal back). It may then be very difficult todiagnose as the detachment may not be easily iden-tified on conventional MRI or even on MR arthrog-raphy (Fig. 99-63) (or at arthroscopy), unless specializedimaging positions such as ABER are employed (Fig.99-63).29,39,341 With distension from MR arthrographyand when needed with ABER positioning, only subtledisplacement of the labral tissue may be seen (seeFig. 99-63).

Anterior LabroligamentousPeriosteal Sleeve Avulsion

The ALPSA lesion342,343 is anterior labroligamentoussleeve avulsion. In these cases the scapular periosteumdoes not rupture, resulting in a medial displacement andinferior rotation of the labroligamentous structures asthey are stripped down to the scapular neck. The ALPSAlesion may then heal in this displaced position. This hasalso been termed a medialized Bankart lesion. A smallcleft or separation can then be seen between the glenoidmargin and the labrum. With a chronic ALPSA lesionfibrous tissue is deposited on the medially displacedlabral ligamentous complex and the entire lesion thenresynovializes along the articular surface. This may leavea deformed and redundant labrum. This lesion mayrequire a different repair from the typical Bankart lesion


A B

F I G U R E 99-59

Labral lesion. A, Anterior labral separation outlined by fluid signal on an axial fast spin-echo T2-weighted image withfat suppression (arrow). The anterior labrum is also blunted and attenuated. B, Axial T1-weighted MR arthrogram(TR/TE 800/20 ms) in another patient. Contrast outlines and imbibes into a complex tear in the anterior labrum (longarrow). Note the attenuated glenohumeral ligament (middle) anterior to this (short arrow).

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and therefore it is important to recognize it.343-345 In theabsence of an effusion the ALPSA lesion may be missedon conventional MRI if the lesion does not extend tothe mid anterior labrum, as the fibrous medializedresynovialized mass may not be well seen on MRIimaging (Fig. 99-64) in a patient with a paucity of jointfluid and magic angle artifact.29 MR arthrography,including the ABER position, may be valuable in reveal-ing these lesion (Fig. 99-64).

Humeral Avulsion of the Glenohumeral Ligament

The HAGL lesion refers to humeral avulsion of theglenohumeral ligament.346-349 This lesion more typicallyoccurs in individuals older than 30 years.349 It may beseen in conjunction with a tear of the rotator cuff orfracture of the greater tuberosity of the humerus. It is notuncommonly associated with a tear of the subscapularistendon. This lesion can be seen on conventional MRI aswell as with MR arthrography (Fig. 99-65).346,347 On MRIexamination the torn glenohumeral ligament may appearthick, wavy and irregular, with increased signalintensity.346 MR arthrography may also show contrastmaterial extravasating from the joint through thecapsular disruption at its humeral insertion. It may befeasible to repair this lesion athroscopically via reattach-

ment to the humerus via sutures. Recently, the HAGLlesion was also seen after successful Bankart repair.350

The bony humeral avulsion of the glenohumeralligaments (BHAGL)351,352 is a rare lesion that may occurafter anterior dislocation of the shoulder. The bonefragment may appear similar to a bony glenoid avulsion.CT or MRI can show that the bone is attached to theglenohumeral ligaments and does not originate from theglenoid but rather from the bone at the site of humeralattachment of the inferior glenohumeral ligament.

Posterior Instability

Posterior instability of the shoulder is not as wellunderstood as anterior stability, in part because it isuncommon but also because of the confusion interminology differentiating posterior subluxations anddislocations.291,353-355

Isolated posterior instability is uncommon andaccounts for only 5% of instability. Acute posteriordislocations of the glenohumeral joint are rare(approximately 2% to 4% of all dislocations of theshoulder).356,357 They may occur following trauma butare commonly associated with electric shocks orseizures. Recurrence is not common.


A

B

C

F I G U R E 99-60

Bankart lesion. A, Axial fast spin-echo T2-weightedimage with fat suppression. There is evidence ofdetachment of the anterior inferior labroligamentouscomplex from the glenoid margin (arrows). B, Axialcadaver section from a specimen subjected to simulateddislocations in the laboratory. Tear and detachment of theanterior labrum is seen with disruption of the capsule andscapular periosteum (black arrows). C, Bankart lesionshowing the anterior labroligamentous tear and detach-ment (black arrow) with disruption of the scapular peri-osteum. (Reproduced with permission from Zlatkin MB.MRI of the Shoulder, 2nd ed. Philadelphia, Lippincott,Williams and Wilkins, 2003. Drawn by Salvador Beltran.)

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Recurrence is very common with atraumaticposterior dislocations and in patients with a history of atraumatic dislocation when large bony defects of thehumerus and glenoid occur. Recurrent posteriorsubluxation rather than dislocation is however the morecommon lesion. Overuse as in athletics is usuallyinvolved. Abduction,flexion,and internal rotation are themechanisms involved (swimming, throwing, andpunching), reflective of repeated microtrauma. Thesepatients, who are often young athletes, may present withpain rather than signs of instability. There may be someassociation with posterior laxity.353-355,358-364

The posterior band of the inferior glenohumeralligament is a primary static stabilizer of the gleno-humeral joint with respect to translation posteriorly ofthe humeral head. Injury sufficient to cause posteriorinstability, however, requires injury to the posteriorinferior labroligamentous complex as well as theposterior capsule. Pathologic findings in patients withprior posterior dislocations and resultant instabilitymay be the reverse of those for recurrent anterior

dislocations and include posterior labral and capsulardetachments and tears, as well as posterior capsularlaxity.365 An impaction type defect on the anteromedialaspect of the humeral head is known as a reverse Hill-Sachs lesion (notch sign or trough lesion). Fractures ofthe posterior glenoid margin and of the lesser tuberositymay also occur. The subscapularis tendon may bestretched or detached, and tears of the teres minortendon may occur. Posterior labrocapsular periostealsleeve avulsion (POLPSA) has also been described.366,367

The MR and MR arthrographic findings associatedwith patients with posterior instability mirror thosedescribed for anterior instability except they involve theposterior capsule and labrum.339,361,368 The reverse Hill-Sachs lesion is well seen on MR images (Fig. 99-66).MRI and MR arthrography may be used to identify thepresence and extent of a tear and detachment ofthe posterior labroligamentous complex (Fig. 99-66).Although the posterior capsule is injured, the capsularabnormalities may be less prominent than in anteriorinstability.339 MR-evident abnormalities that involve


A

B

C

F I G U R E 99-61

Bankart lesion. A, Axial T1-weighted MR arthrogramwith fat suppression. There is evidence of detachment ofthe anterior inferior labroligamentous complex from theglenoid margin (true “Bankart” lesion) (arrow). B andC, Axial T1-weighted MR arthrograms with fat suppres-sion. Similar findings of a labroligamentous tear anddetachment are seen (white and black arrows in B, largearrow in C). Note the small defect in the posterior labrum(small arrow in C) and subjacent fragment (arrowhead).

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A B

F I G U R E 99-62

Bankart lesion. A, Axial fast spin-echo T2-weighted image with fat suppression. Note the injury to the anteriorcapsulolabroligamentous complex with disruption of the scapular periosteum (white arrows). The labralseparation/detachment is not as well depicted as when the joint is distended with MR arthrography (see Fig. 99-61)Also note the acute Hill-Sachs lesion (black arrows). B, Sagittal fast spin-echo T2-weighted image (TR/TE 3000/72 ms)with fat suppression. Sagittal oblique images help reveal the extent of the injury, from superior to inferior (arrows)(see also Fig. 99-58).

A B

F I G U R E 99-63

Bankart lesion variants. Perthes lesion. A, Axial T1-weighted MR arthrogram. The anterior labroligamentous complexhas healed back in a near normal position. The MR arthrogram outlines subtle displacement of the labral tissue(arrow). B, Axial oblique abduction and external rotation (ABER) T1-weighted MR arthrogram in another patient.Again only subtle displacement of the labral tissue is seen (arrow).

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A

B

C

F I G U R E 99-64

Bankart lesion variants. Chronic anterior labroliga-mentous periosteal sleeve avulsion (ALPSA) lesion.A, Axial fast spin-echo T2-weighted image with fatsuppression. The fibrous medialized resynovialized massof intermediate signal intensity (arrow) is difficult todiscern on conventional MR images. B, Axial T1-weighted MR arthrogram. A cleft of contrast materialoutlines the anteromedially displaced healed-over massof labroligamentous tissue (arrow). C, Axial obliqueT1-weighted image taken in the abduction and externalrotation (ABER) position reveals the cleft of contrast(black arrow) and the thickened anteromedially displacedmass of labroligamentous tissue (white arrow).

F I G U R E 99-65

Humeral avulsion of the glenohumeral ligament (HAGL).Axial fast spin-echo T2-weighted image with fat sup-pression. The humeral attachment of the glenohumeralligament is markedly abnormal in signal intensity andmorphology (arrow).

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the bony glenoid include fractures or defects, althoughfindings of marrow edema or sclerosis and cystic lesionsmay also be identified. In patients with atraumaticrecurrent posterior subluxation, joint laxity with redun-dancy of the posterior capsule may be the most promi-nent finding and a posterior labral tear may not befound.354 This may also be associated with inferiorredundancy353,369 in which case multidirectional insta-bility may result. MR arthrography may be the onlymeans of imaging able to reveal this laxity.

Isolated Labral Tears

The labrum can tear in the absence of subluxation ordislocation. The tears that have been described in thiscircumstance include flap or bucket-handle tears andthese lesions may be present in the anterior superiorportion of the labrum. They may respond to arthroscopicexcision. Isolated glenoid labrum lesions may occur inthe throwing athlete as fraying or separation in thesuperior quadrant of the labrum adjacent to the origin ofthe long head of the biceps. These patients presentwith a painful catching or snapping sensation duringthrowing. This is related to overloading of the bicepstendon and subsequent avulsion of the superior part ofthe labrum during the follow through. These lesions inthe labrum may be associated with pathology in therotator cuff. Injuries seen in the rotator cuff are oftenpartial tears of the rotator cuff undersurface more pos-teriorly. MR arthrography may reveal these lesions best,as contrast will leak into the labral tears, imbibe intoareas of labral fraying, detect areas of labral separationor detachment, and leak or imbibe into undersurfacerotator cuff injuries.

Posterosuperior subglenoid impingement (see earlier)occurs during the late cocking phase of throwing withabnormal contact between the posterosuperior portionof the glenoid rim and the undersurface of the rotatorcuff, and is thought to occur at the extremes of abduc-tion and external rotation. A triad of findings has beendescribed in association with this lesion (Figs. 99-34 and99-67): injury to the rotator cuff undersurface at thejunction of the infraspinatus and supraspinatus tendons;degenerative tearing of the posterosuperior glenoidlabrum; and subcortical cysts and chondral lesions in theposterosuperior glenoid and humerus due to repetitiveimpaction. There may in addition be an injury to theinferior glenohumeral ligament because it limitsabduction in external rotation of the glenohumeral jointand is therefore under tension in this position.

SLAP Lesions

Snyder et al370-372 introduced this term to define injuriesto the superior portion of the labrum and adjacentbiceps tendon. A superior quadrant labral tear withanterior and posterior components of the tear is labeleda SLAP lesion (superior labrum anterior posterior). Thelesion may be acute or chronic and when acute they mayresult from a fall onto the outstretched arm with theshoulder in abduction and forward flexion. It also mayoccur in athletes repetitively overusing the arm,295,373-375

including baseball, tennis,or volleyball players. The injuryto the superior portion of the glenoid labrum may resultfrom sudden forced abduction of the arm, i.e., excessivetraction related to a sudden pull from the long headof the biceps tendon. The lesion may typically beginposteriorly and then extend anteriorly and terminate at


A B

F I G U R E 99-66

Posterior instability. A, Axial T2-weighted (TR/TE 3100/47 ms) fast spin-echo image with fat suppression. Theposterior glenoid labrum and capsule are torn along the posterior glenoid margin (short arrow). There is a bony defecton the anteromedial aspect of the humeral head consistent with a “reverse Hill-Sachs deformity.” It is associated withmarrow edema (long arrow). B, Sagittal oblique T2-weighted fast spin-echo image with fat suppression, carried outafter intra-articular fluid injection. The superior inferior extent of the labral tear/detachment is seen best in thisprojection, outlined by the fluid signal and joint distension (arrows).

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or before the midglenoid notch. It includes the bicepslabral anchor.

SLAP tears were categorized into four basic typesby Snyder et al.372 Type 1 (10% of SLAP lesions) revealssuperior labral roughening and degeneration. The labrumremains firmly attached to the glenoid. This lesion mayrepresent a degenerative tear of the labrum. Type 2 is themost common lesion (40%) and is a detachment of thisroughened superior portion of the labrum and itsbiceps tendon anchor. Burkhart et al295,374 describedthree distinct categories of type 2 SLAP lesions: anterior,posterior,and combined anteroposterior. Type 3 (30%) isa bucket-handle tear of the superior portion of thelabrum. It does not involve the biceps labral anchor.Type 4 (15%) has in addition to the bucket handle tear asplit tear of the biceps tendon.

Additional types of SLAP lesions have beendescribed.273,373,376,377 Type 5 is a Bankart lesion of theanterior inferior labrum that then extends superiorly toinclude separation of the biceps tendon anchor. Type 6lesions are unstable radial or flap tears that also involveseparation of the biceps anchor. A type 7 lesion consists

of anterior extension of the SLAP lesion to involve themiddle glenohumeral ligament. Type 8 lesions extendposteroinferiorly with extensive detachment of theposterior labrum. A type 9 lesion is a complete con-centric avulsion of the labrum circumferentially aroundthe entire glenoid rim.375

MRI and MR arthography may be used in the detec-tion of SLAP lesions (Figs. 99-68, 99-69, 99-70, and99-71).273,376,378-383 In the study by Cartland et al384 onMRI examination, type 1 lesions exhibited irregularity ofthe labral contour with mildly increased signal intensity.Type 2 lesions may have revealed a globular region ofincreased signal interposed between the superiorlabrum and glenoid margin. Type 3 showed typical linearincreased signal extending to the labral surface. Type 4lesions showed high signal within the superior labrumand extending into the proximal biceps tendon. SLAPlesions may be difficult to detect on conventional MRimaging. The more superior portions of the tear can bedifficult to visualize on axial images. External rotation,as well as coronal oblique images, help define theselesions.382 MR arthrography can be very helpful in


A B

C

F I G U R E 99-67

A, Axial; B, coronal; and C, sagittal oblique T1-weightedimages after intravenous gadolinium injection for intra-venous MR arthrography. The rotator cuff showstendinosis more posteriorly (arrowhead in B). There iscystic change in the humeral head posterosuperiorly(black arrow in A). The labrum imbibes contrast,reflective of degenerative-type tearing (white arrows).Findings are consistent with posterosuperior glenoidimpingement.

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AB

C

F I G U R E 99-68

Superior labrum anterior posterior (SLAP) lesion.A, Axial, and B and C, coronal oblique fast spin-echoimages (B, anterior; C, more posterior) with fat suppres-sion. A continuous tear and detachment is identified inthe superior labrum, anterior and posterior (SLAP type 2)(white arrows in A-C).

F I G U R E 99-69

Superior labrum anterior posterior (SLAP) lesion. Type 3lesion. Coronal oblique T1-weighted MR arthrogram.Contrast extension reveals detachment and milddisplacement of the superior labrum from the glenoid rim(arrow). The biceps tendon insertion remains intact(arrowhead). (Courtesy of Javier Beltran MD, New York.)

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detecting SLAP lesions, including the use of traction insome select situations.385 It will distend out buckle-handle type tears, outline morphologic alterations, andimbibe into areas of degeneration and fraying of thelabrum and biceps tendon. MR arthrography demon-strates the following signs in SLAP lesions386: 1. contrastmaterial may extend superiorly into the glenoid attach-ment of the long head of the biceps tendon (LHBT) on

oblique coronal images; 2. irregularity of the insertion ofthe LHBT on oblique coronal and sagittal images;3. accumulation of contrast material between the labrumand glenoid fossa on axial images; 4. detachment anddisplacement of the superior labrum on oblique sagittaland coronal images; and 5. a fragment of the labrumdisplayed inferiorly between the glenoid fossa and thehumeral head. In addition, as noted later, a paralabral cyst


BA

A B

F I G U R E 99-71

Superior labrum anterior posterior (SLAP) lesion. Type 8 lesion. A, Axial fast spin-echo T2-weighted image (TR/TE3000/55) with fat suppression. B, 2D gradient-echo image (TR/TE 400/22 ms, flip angle 25 degrees). There is a tearof the superior labrum which extends posteroinferiorly (arrows).

F I G U R E 99-70

Superior labrum anterior posterior (SLAP) lesion. Type 4 lesion. A, Axial and B, coronal oblique fast spin-echoimages with fat suppression. A tear is identified in the superior labrum, anterior and posterior (long arrows) extendinginto the proximal biceps tendon (short arrow in B).

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may be frequently associated with these lesions. In onestudy MR arthrography had a sensitivity of 89%, aspecificity of 91%, and an accuracy of 90%.376

Tears of the superior portion of the labrum must bedistinguished from the normal variants of the labrum andits attachments in this region. Among the criteria fordistinguishing these lesions from SLAP tears are thatthese lesions do not extend to involve the superior orposterior labrum beyond the level of the biceps labralanchor and there should be no associated morphologicalterations. In addition they should not extend below thelevel of the equator of the glenoid which may be markedby the coracoid process. Increased distance between thelabrum and the glenoid, an irregular appearance of thelabral margin, or lateral extension of the separation maysuggest a SLAP lesion rather than a normal anatomicvariant.380 As with other tears of the superior labrum,SLAP lesions are frequently associated with rotator cufflesions, particularly partial tears. One study found suchlesions in 42% of cases.376

Paralabral Ganglion Cysts

These are ganglion cysts arising adjacent to the glenoidlabrum387-389 and most commonly associated with alabral tear (see Figs. 99-72 and 99-73). This labral tear isoften a SLAP lesion and the paralabral cyst mostcommonly arises in relation to the posterosuperior com-ponent (Fig. 99-72). It may, however, occur anywhere inthe glenohumeral joint. Pathophysiologically they maybe similar to cysts of this nature elsewhere in the body,such as meniscal cysts or cysts associated with tears ofthe acetabular labrum. In this situation fluid arising fromthe joint extends through the labral tear into thesurrounding soft tissues and leads to ganglion cystformation. Paralabral cysts may be difficult to identifyon MR arthrography unless some form of T2-weightedsequence is performed as direct communication betweena cyst and the joint space rarely occurs (see Fig. 99-46).A posterior or inferior cyst may cause compressionneuropathy of the suprascapular or axillary nerve,respectively. Compression of the suprascapular nerve is


A B

C

F I G U R E 99-72

Paralabral cyst. A, Axial; and B and C, (both posterior)coronal oblique fast spin-echo T2-weighted sequenceswith fat suppression. A large paralabral cyst is identified(long arrows) arising in relation to a posterosuperiorlabral tear (short arrows) and extending into thespinoglenoid notch region.

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usually with extension of the posterior cyst into thespinoglenoid notch. Cysts that cause nerve compressionare usually large (mean size 3.1 cm). Infraspinatus muscleatrophy may be seen (Fig. 99-73). Compression of theaxillary nerve may be an unusual cause of quadrilateralspace syndrome.390 Atrophy of the teres minor musclemay also be seen.

Glenoid Labrum Articular Disruption

Another recently described lesion occurs in athletes andhas been described at arthroscopy.391 The GLAD lesion(glenoid labrum articular disruption) is a tear of thesuperficial anterior inferior labrum and also involvesarticular cartilage (Fig. 99-74). It results from a forcedadduction across the chest from an abducted andexternally rotated position. The labral tear is an inferiorflap-type tear. It is not associated with glenohumeralinstability. In addition, there is fibrillation and erosion ofthe articular cartilage in the anteroinferior quadrant ofthe glenoid fossa. These lesions may be visible on MRIand MR arthrography may improve the sensitivity tothese lesions.392,393

Glenohumeral Internal RotationDeficit in Abduction

This refers to the concept proposed by Burkart andMorgan295,374,394 that reflects the fact that many of theproblems associated with shoulder disability in olderthrowing athletes is due to contracture and thickening ofthe posterior inferior capsule, which results in aglenohumeral internal rotation deficit in abduction

(GIRD). This is associated with secondary hyper-external rotation. Other associated lesions include theposterior peel back lesion of the glenoid labrumfrom the biceps tendon insertion to the posterior supe-rior labrum,324,394,395 SLAP type 2 lesions, and dead armsyndrome.374 Shear and torsional forces result ininjury to the posterosuperior aspect of the rotator cuff.Although lesions similar to those described in posteriorsuperior glenoid impingement are seen, the posteriorinferior capsular lesion rather than the act of subglenoidimpingement is considered to be the underlying cause.The anterior capsular stretching, often seen in olderthrowing athletes, is also considered to be secondary tothe posterior capsular contracture. These lesions,including the presence of posterior capsular thickening,may be best outlined with MRI arthrography (Fig.99-75).

POSTOPERATIVE SHOULDER

Imaging the postoperative shoulder is challenging bothfrom an imaging point of view and a technical point ofview.396-405 Certain technical factors must be taken intoconsideration. Postoperative artifact is problematic inimaging the postoperative patient. This includes ferro-magnetic screws or staples. Small metal shavings fromthe use of a burr during acromioplasty may yield con-siderable artifact. The use of gradient-echo sequencesshould be minimized and fast spin-echo imaging isuseful to minimize the degree of magnetic susceptibilityartifact. Additionally, fat saturation may be incompleteand fast spin-echo inversion recovery sequences may bemore useful. MR arthrography can be a useful tool tohelp image postoperative patients more successfully.


A B

F I G U R E 99-73

Paralabral cyst. Infraspinatus atrophy. A, Axial fast spin-echo T2-weighted sequence and B, coronal oblique fastspin-echo T2-weighted sequence with fat suppression. A paralabral cyst is identified (short arrows) which extends intothe spinoglenoid notch region. Note the atrophy of the infraspinatus muscle (long arrows in A).

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Impingement and Rotator Cuff Disease

Subacromial Decompressionwithout Rotator Cuff Repair

Surgical Technique

The first category of postoperative patients is those whohave had a prior acromioplasty for impingement with anintact rotator cuff and no rotator cuff repair. Thisprocedure may be done open,via an anterolateral deltoidsplitting incision, or via arthroscopy. The anteroinferioracromion is removed, from the acromioclavicular joint tothe deltoid insertion, removing that portion anterior tothe clavicle. Most often the subdeltoid bursa is alsoresected as well as a variable part of the coracoacromialligament. The acromioclavicular joint and the distal2.5 cm of the clavicle may also be removed.

MRI Findings

MRI findings associated with acromioplasty include aflattened acromial undersurface, nonvisualization of theanterior one third of the acromion, and decreasedmarrow signal in the remaining distal acromion due tomarrow fibrosis. Low signal due to artifacts from smallmetal fragments are often present, related to burring ofthe acromion. Removal of the subacromial bursa andsubdeltoid fat pad results in the absence of thesestructures on postoperative studies, and most often asmall amount of fluid signal on images with T2contrast. If the acromioclavicular joint has been excised,scar tissue may be the most prominent finding (Fig.99-76).397,400,403,405

Causes of persistent pain after subacromial decom-pression include inadequate acromioplasty and residualosteoarthrosis of the acromioclavicular joint (Fig. 99-77).Sagittal oblique MR images evaluate the adequacy of thedecompression and any persistent impingement due toinsufficient acromion resection or the persistence of alarge subacromial spur. Large osteophytes projectingfrom the acromioclavicular joint may be seen on coronaland sagittal images. After acromioplasty, there may beprogression of rotator cuff disease, including the inter-val development of a rotator cuff tear, partial or com-plete (Fig. 99-77). Unrecognized partial tears or smallcomplete tears may extend. Progression may occur ifthe acromioplasty and decompression are inadequate,with persistent subacromial roughening.397,400,403,405

In the setting of interval development of a cuff tear orextension and/or progression of existing cuff pathology,such as tendinosis, the integrity of the cuff is moredifficult to determine in the postoperative situation. MRIremains sensitive but less specific than MRI withoutprior surgery. Criteria include a definite region of dis-continuity in the cuff, accompanied by fluid signal onimages with T2 contrast, STIR or T2*-weighted gradient-echo sequences, or when contrast extravasation is seenthrough the cuff defect at MR arthrography (see Fig.99-77).397,400,403,405

Rotator Cuff Repair or Debridement

Surgical Technique

The second category involves patients who have had aprior rotator cuff repair. In patients with partial-thicknesstears, treatment depends on the area, depth, and severity


A B

F I G U R E 99-74

Glenoid labrum articular disruption (GLAD) lesion. A and B, Axial 2D gradient-echo images. There is a tear of theanterior inferior labrum (arrow in B). It is associated with an osteochondral-like lesion of the inferior anterior marginof the glenoid articular surface (arrow in A). The capsuloligamentous structures are intact.

099.qxd 17/6/05 12:56 PM Page 3260

of tendon involvement. Treatment may vary fromdebridement of frayed tissue in more superficial partialtears, to completely excising the area of the partialdefect and repairing the defect as if it were a small full-thickness defect. Repairs of high-grade partial- orfull-thickness tears are either a side-to-side or tendon-to-bone repair and may be accompanied by decom-pression. This may be done arthroscopically, open, orwith a combined approach.

MRI Findings

MRI findings following cuff repair (Fig. 99-78) includedistortion of the soft tissues adjacent to the cuff and

nonvisualization of the subdeltoid fat/bursa and fluid inthe region of the subdeltoid bursa. Soft-tissue metal orsuture artifacts occur due to nonabsorbable sutures andsuture anchors, especially if ferromagnetic sutureanchors are used.Granulation tissue surrounding suturesmay result in intermediate or high signal on images withT2 contrast in the peritendinous tissues. A surgicaltrough in the humeral head is present with tendon-to-bone repairs. Intermediate signal within the rotator cuffsubstance may be present due to granulation tissue. Mildsuperior subluxation of the humeral head may occur dueto capsular tightening, scarring, cuff atrophy, orbursectomy. Mild marrow edema in the humeral headmay be seen.397,400,403,405


A B

C D

F I G U R E 99-75

Glenohumeral internal rotation deficit (GIRD). A, Axial T1-weighted MR arthrogram. Note the thickened postcapsule at the site of insertion into the glenoid (arrow). B, Coronal oblique T1-weighted MR arthrogram in the samepatient as in A. Note the alterations in the posterior rotator cuff (long arrow), the degenerative-type tear ofthe posterior superior labrum (short arrow), and the cystic changes in the humeral head (arrowhead). C, AxialT1-weighted MR arthrogram in a different patient. Note the thickened posterior capsule, similar to that in A (arrow).D, Axial T1-weighted MR arthrogram in the same patient as in C. Note the superior labrum anterior posterior(SLAP) type 2 tear of the superior labrum (arrows).

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Fluid signal on T2-weighted images seen within arecurrent rotator cuff tendon defect or nonvisualizationof a portion of the cuff are the more reliable indicatorsof full-thickness tears in the postoperative patient, withcomplete absence of the tendon the most specificfinding. In the postoperative situation there may be ahigher incidence of low signal tears due to chronicgranulation tissue. Secondary signs such as muscleatrophy and tendon retraction may be helpful (Fig.99-79). MR arthrography can document leakage ofcontrast through a cuff defect directly, and the cufftissues and tendon edges may be better delineated withthis technique (Fig. 99-80). The location of the musculo-tendinous junction is not a reliable sign after surgerybecause its position may change if the cuff is mobilizedduring surgery.397,400,403,405

The criteria for a recurrent partial tear is fluid signalon images with T2-weighted contrast replacing a portionof the tendon.Small recurrent full-thickness tears may beunderestimated as partial tears. MR arthrography mayhelp to resolve these difficulties.397,400,403,405

Deltoid Detachment

Postoperative detachment of the deltoid from itsinsertion to the acromion may occur.On MRI images, thepresence of deltoid detachment can be identified by

retraction of the deltoid from the acromion with fluidfilling the defect.397,406,407 If the detachment is chronic,atrophy will be present.

Biceps Tendon Rupture

MRI is accurate in the diagnosis of biceps tendonrupture in patients after surgery. This is diagnosed bylack of visualization of the biceps tendon in the inter-tubercular groove.

Shoulder Instability

Surgical Approach

The surgical treatment of patients with anteriorinstability has involved different approaches. Mostcommonly a direct repair of the labral and capsularlesions is done, usually a Bankart-type repair, or lesscommonly staple capsulorraphy. Other types of repairare those that tighten the capsule indirectly, usuallythrough manipulation of the subscapularis, most com-monly the Putti Platt or Magnusson-Stack procedure, andthose that involve movement of the coracoid process,most commonly the Bristow procedure.


A

B

C

F I G U R E 99-76

Status post acromioplasty, distal clavicle excision.A, Coronal oblique proton-density–weighted image. Theanterior portion of the acromion has been removed(arrow). Also note the low signal post-surgical artifact.B, Sagittal oblique proton-density–weighted image. Theextent of the decompression is often best seen in thisposition. The anterior acromion, acromioclavicular joint,and distal clavicle have been excised (arrow). C, CoronalT2-weighted image. Increased signal or fluid is oftenidentified in the subdeltoid bursal region post decom-pression, due to accompanying resection or debride-ment of the bursa. The bursal surface of the tendon isthin, likely post debridement (short arrow). There has beenan acromioplasty and distal clavicle excision (long arrow).

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A

B

C

F I G U R E 99-77

Postacromioplasty pain. A, Coronal oblique T2-weightedfast spin-echo sequence with fat saturation. There ispersistent acromioclavicular joint arthritis with marginaledema (long arrow). A small undersurface partial tear isalso seen (short arrow). B, Coronal oblique T1-weightedMR arthrogram. The patient has had an acromioplasty.There is an intermediate-grade undersurface partialthickness tear (arrow). C, Coronal oblique, fast inversion-recovery sequence in another patient. The patient hashad an anterior acromioplasty. There has been intervaldevelopment of a full-thickness tear of the supraspinatustendon, anterodistally (arrow).

A B

F I G U R E 99-78

Postoperative shoulder. Rotator cuff repair. A and B, Coronal oblique proton-density–weighted images. There hasbeen a tendon-to-bone repair (short arrows). Note the bone trough for the sutures (arrowhead in B). There has beenan acromioplasty (long arrow in A).

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A

B

C

F I G U R E 99-79

Recurrent rotator cuff tear. Coronal oblique A, proton-density– and B, T2-weighted fast spin-echo sequencewith fat saturation. There is a recurrent full-thicknesstear (long arrows). The tendon is retracted medially withthin edges. Note the site of repair (short arrows). There ispersistent subacromial spur formation and acromoclav-icular joint osteoarthritis. C, Sagittal oblique T1-weightedimages. Note the muscle atrophy and fat infiltration(arrows).

F I G U R E 99-80

Coronal oblique T1-weighted MR arthrogram. A mod-erate size recurrent tear of the supraspinatus tendon isidentified (arrow). Depiction of the tear size and status ofthe tendon edges is aided by MR arthrography.

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Normal Postoperative MRI Findings

The artifacts from surgery impair visualization, includingmetal and suture artifacts, especially screw fixation ofthe coracoid in the Bristow procedure, or the placementof suture anchors, staples, or tacks. Scarring fromthe incisions as well as suture repair may impairvisualization. In Bankart repairs (Fig. 99-81) evennonferromagnetic suture anchors may be apparentwithin the glenoid neck. If transglenoid sutures areplaced, channels will be seen traversing the glenoidneck and scapula. In addition the suture knot placedposteriorly, i.e., tied over fascia, may show somesurrounding intermediate or high signal on images withT2-type contrast due to hyperemic granulation tissue. Inpatients with anatomic repairs, such as the Bankartrepair, there should be an anatomic position andmorphology of the labrum and capsule post repair. Inprocedures that do not directly repair the labral andcapsular lesions, as noted earlier, the abnormality fromthese lesions remains.396,397,408

Recurrent Lesions

Causes of recurrent instability (Fig. 99-82) includeinadequate or incorrect procedures and the uncoveringof missed anterior or posterior instability with isolatedtreatment of one. An overtight repair can lead either todegenerative change or may precipitate instability inthe other direction. This may be more common inprocedures such as the Putti Platt or Magnusson-Stack,which may also result in loss of external rotation. Inferior

capsular shifts or other types of capsular plications canalso be overtightened. Signs of an overtightened inferiorcapsular shift include loss of the axillary pouch andsubtle posterior subluxation of the humeral head relativeto the glenoid. Degenerative arthritis may also occur ifthere is persistent instability from inadequate repair.Misplaced or detached staples, tacks or anchors (Fig.99-83) from labral and capsular repairs or misplacedscrews or coracoid nonunion in a Bristow proceduremay also cause joint derangement. If left unrecognized itmay lead to degenerative changes as well.

In patients after repair of the labrum and capsule thepostoperative labrum may be thickened and irregulardue to scar tissue or suture material, but should notbe detached. Signal alterations may be present post-operatively and high signal on images with T2 contrastmay be present in the earlier postoperative periods dueto hyperemic granulation tissue.399 As such, outliningthe labrum and capsule with intra-articular contrastis the best means of discerning recurrent tears anddetachments, by outlining any surface irregularitiesand revealing any contrast extension into or beneaththe labrum.401,409 Failed Bankart repairs may showpersistence or recurrence of the detached labrumand capsule. This may occur due to breakdown of thefixation from suture breakage, anchor device pullout,or failure of the reapproximated labral and capsulartissues. The repaired labrum may also become blunted,attenuated, or fragmented.

Postoperatively the joint capsule may appear thick-ened and nodular. Measurements of capsular thickeninghave been described for adhesive capsulitis,410 andcan be measured best in the axillary recess on MR


A B

F I G U R E 99-81

Post Bankart repair. A, Axial turbo spin-echo T2-weighted image. Note the artifact from the suture anchor in theanterior inferior glenoid (short arrow). Low signal from scarring of the labroligamentous tissue is noted after surgery(long arrows). B, Sagittal oblique fast spin-echo proton-density–weighted image in another patient. Post-surgicalartifact outlines the sites of fixation in the anterior glenoid (arrows).

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arthrography as a band of low signal adjacent to thehyperintense signal of contrast medially, and the hyper-intense signal of the fat stripe laterally on T1-weightedimages. A measurement of 4 mm indicates adhesivecapsulitis and one of 2 to 4 mm is considered consistentwith the thickening expected after Bankart repair. Theglenohumeral ligaments may also appear thickened andnodular post repair. In patients with recurrent instabilitythe repaired capsule may become stretched andredundant. These changes are best identified by MRarthrography. Rand401 indicates that an anterior capsularwidth/posterior capsular width ratio of less than 1 onMR arthrography may predict a good outcome post sur-gery,particularly if a capsulorraphy,open or arthroscopic,has been done. The glenohumeral ligaments, if abnormal,may appear thin, elongated, irregular, and discontinuous.

OTHER DISORDERS

Occult Fractures

Occult fractures of the proximal humerus often involvethe greater tuberosity and occur as a result of injuriessuch as seizures, glenohumeral dislocations, and forcedabduction. Mason et al170 described the MRI findings ofoccult greater tuberosity fractures in 12 patients inwhom plain films failed to demonstrate minimallydisplaced fractures. All patients had partial tears ortendinosis of the rotator cuff,but none had full thicknesstears. These authors postulate that the presence of afracture precludes a full-thickness tear of the cuff.Conversely, Zanneti et al411 found nondisplaced greatertuberosity fractures in 9 of 24 patients following acute

substantial trauma to the shoulder associated withcomplete tears of the supraspinatus, infraspinatus, andsubscapularis tendons.411

MRI demonstrates the fracture line as a low signalirregular area surrounded by bone marrow edema (Fig.99-84). Clinically, these patients present with symptomsthat simulate rotator cuff tears.


A B

F I G U R E 99-82

Post Bankart repair. Recurrent lesion. A and B, MR arthrogram. Axial T1-weighted images with fat suppression(B is inferior to A). The anterior inferior labrum is detached (white arrow in A). Note is also made of early gleno-humeral joint degenerative change. Note the small osteophytes projecting from the humeral head in A (black arrows).There is bone loss along the inferior glenoid (arrow in B). A Hill-Sachs lesion is present (arrowhead in A).

F I G U R E 99-83

Displaced anchor. Sagittal oblique T1-weighted MR arthrogram with fatsuppression. Note the displaced suture anchor (arrow) from a prior Bankartrepair (arrowhead) in the posterior inferior joint recess.

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Muscle Injuries

Muscle contusions, hematomas, and ruptures mayinvolve the muscles of the shoulder girdle, not only therotator cuff muscles such as the subscapularis, but alsothe surrounding musculature such as the deltoid,trapezius,or pectoralis muscles.412-414 Muscle hematomasmay have high signal intensity on both T1- andT2-weighted images (Fig. 99-85). Complete rupture ofthe muscles of the shoulder girdle such as the deltoid,pectoralis, or triceps are relatively uncommon lesions.

Evaluation of pectoralis major ruptures with MRI (Fig.99-85) has been described.415-418 This occurs mostcommonly in weightlifters.Fat-saturated T2-weighted fastspin-echo sequences in the axial plane with surface coilsare the most useful in diagnosing this lesion and itsextent. Surgical repair of these lesions is difficult but itis likely that MRI can be very helpful if surgery iscontemplated, to assess the extent, type, and pattern ofrupture, and determine the status of the torn muscle andtendon edges.


A B

F I G U R E 99-84

Occult greater tuberosity fracture. A, Coronal oblique proton-density image and B, T2-weighted image. A linearregion of low signal represents the fracture line (curved black arrows). There is adjacent marrow edema. There isevidence of injury (strain or contusion) to the cuff and fluid in the bursa (white arrows), but no cuff tear.

A B

P

H

F I G U R E 99-85

Pectoralis major rupture. A, Axial T1-weighted image. In the acute phase the muscle rupture is manifested by andobscured by a focal hematoma. Note the high signal mass (arrows). B, Axial T2-weighted fast spin-echo image withfat saturation. The retracted torn pectoralis muscle and tendon are now evident (arrows). H, humerus; P, pectoralismajor muscle.

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Inflammatory and DegenerativeJoint Processes

Many forms of inflammatory and degenerative jointprocesses involve the shoulder. These include rheuma-toid arthritis, ankylosing spondylitis, other seronegativespondyloarthropathies, and degenerative arthritis.419-423

Involvement of the shoulder is not uncommon inrheumatoid arthritis and its variants, particularly in long-standing disease. Osseous erosions occur predominantlyon the humeral side of the joint. The acromioclavicularjoint is also often involved.197 Inflammatory arthritis mayalso affect the surrounding bursae, muscles, and rotatorcuff tendons.388,424,425 Although loss of articular cartilageand osseous erosions may be observed with conven-tional radiography, they may be visualized at an earlierstage with MRI and their extent may be better assessed.Soft-tissue changes, including rotator cuff atrophy andtears, inflammation of the subacromial bursa, ruptures ofthe biceps tendon, and synovial cysts can also beidentified with MRI.419,421,425,426 MRI can be used tofollow patients to assess the response to medical therapy.Intravenous gadolinium injection is useful in differen-tiating a joint effusion from acutely inflamed synovium(Fig. 99-86).426

In septic arthritis MRI may be particularly useful inestablishing an early diagnosis and determining theextent of the disease. This is important as septic arthritisin the shoulder in adults rarely responds well to treat-ment. Early joint aspiration still needs to be performedfor definitive diagnosis and to obtain fluid for culture.Tears of the rotator cuff may be associated with septic

arthritis of the shoulder and can be documented onMR images. This is likely related to erosion of the infe-rior aspect of the tendon by inflamed synovium. Thepresence of a cuff tear may be more responsible for apoor functional result after treatment than damage tothe articular cartilage. MRI may also be helpful indocumenting extra-articular spread of infection, such ascavities that may communicate with the joint space.When osteomyelitis develops, MRI407 will show marrowedema on short TR/TE, fast spin-echo T2-weightedimages with fat suppression, or STIR images.

Degenerative arthritis in the absence of prior trauma,or an underlying systemic disorder, is uncommon in theshoulder (see Fig.99-86).Changes observed include jointspace narrowing, sclerosis of the subchondral bone andcyst formation that involves the glenoid and humeralhead. Osteophytes may be seen at the circumference ofthe glenoid fossa, along the inferior aspect of thehumeral head and adjacent to the bicipital groove.MRI israrely required to assess patients for this clinical problemalone,but may on occasion be found on imaging patientswith shoulder pain suspected of other disorders.Degenerative joint disease of the acromioclavicular jointis very common, particularly in older patients. It maycontribute to rotator cuff disease and shoulder impinge-ment, but may also be a source of shoulder pain.Ganglion cysts may develop in relation to this joint.

Other synovial processes, such as pigmentedvillonodular synovitis (PVNS) or synovial osteochon-dromatosis, may be visualized with MRI. The shoulder isthe fourth most common site of involvement of PVNS,but is still a rare site of involvement.427,428 On MRI,nodules and villous projections of synovium which


A B

F I G U R E 99-86

Osteoarthritis. Intravenous gadolinium, synovitis. A, Coronal oblique T2-weighted image. Severe joint spacenarrowing, subchondral sclerosis, and osteophytes are present. There is a massive subdeltoid bursal effusion.B, Coronal oblique T1-weighted image after intravenous gadolinium injection with fat saturation. Areas ofenhancement in the joint and bursa represent acutely inflamed synovium superimposed on the degenerative process(arrows).

099.qxd 17/6/05 12:56 PM Page 3268

contain hemosiderin are seen as areas of intermediatesignal intensity on all pulse sequences. There is usually alarge joint effusion and periarticular cysts may develop.Cystic erosions may be evident as well-defined areas oflow signal intensity on short TR/TE images and increasedsignal intensity on long TR/TE images. Hemosiderindeposition is more apparent on gradient-echo sequencesbecause of increased susceptibility effects.

Idiopathic synovial osteochondromatosis (SOC) is achronic, progressive, monoarticular disorder causedby metaplasia of the synovial membrane, with the for-mation of numerous cartilaginous intra-articular nodules.Shoulder involvement is less common than that of thehip and knee.429 MRI can be helpful in verifyingthe diagnosis and can demonstrate the nodules, even ifthese are not calcified.430-432 Calcified nodules appearas areas of low intensity on short TR/TE, proton-density–weighted, and long TR/TE images (Fig. 99-87).Nodules that do not calcify should have a high signal onlong TR/TE images due to the abundant water content ofhyaline cartilage, with interspersed areas of low signaldue to fibrous tissue between the cartilage nodules. Thesurrounding tissue may include areas of inflamed and/orhyperplastic synovium and reactive fluid.

Osteocartilaginous loose bodies are usually fragmentsof bone and cartilage that may be sheared off the glenoidor humeral head, often secondary to osteochondralfractures. Other causes of loose bodies include osteo-arthritis and neuropathic disease. Osteocartilaginousloose bodies may occur in the joint of patients withrecurrent shoulder dislocations. These may result fromHill-Sachs lesions or may be fragments from fractures ofthe glenoid rim. Clinically, they may cause recurrenteffusions, a locking or grating sensation, as well as adecreased range of motion. More commonly, they fallinto the inferior capsular recess and do not produce any

significant problem. In general, MRI is not the procedureof choice to identify loose bodies. When encountered,densely calcified loose bodies on MRI appear as lowsignal intensity structures.When ossified they may be ofhigh-to-intermediate signal with a low signal intensityrim due to the presence of mature marrow elementswithin.MRI arthrography may be helpful to outline someof these lesions by distending the joint and by improvingoverall contrast resolution.

Osteochondral Lesions

Osteochondral lesions of the shoulder are rare. Differentnames and descriptions have been used by differentauthors to describe a group of lesions that involve thearticular surface of the glenoid fossa, including osteo-chondritis dissecans (OCD),433 subchondral avascularnecrosis,434 juxta-articular bone cyst or post-traumaticsubchondral cyst,435 and glenoid articular rim divot(GARD).370,371,436 These lesions may be related to acutetrauma and are often associated with glenohumeralinstability, labral tears, and intra-articular loose bodies(Fig. 99-88).433 Cystic changes in the subchondral boneof the glenoid fossa are the most frequent feature.Occasionally, loose bodies are found. Careful attention tothe articular surface of the glenoid may reveal thepresence of a chondral or osteochondral defect.

The glenoid articular rim divot (GARD) has beendescribed based on arthroscopic findings.370,371 MRIexamination in these patients may reveal the chondraldefect as well as a cartilaginous loose fragment in a jointrecess. A similar entity was reported by Chan et al437 inwhich multiloculated subchondral cysts are present inthe posterior superior quadrant of the glenoid fossa.These authors used the same acronym,GARD, to indicate


A B

F I G U R E 99-87

Synovial osteochondromatosis. A, Coronal oblique T2-weighted fast spin-echo image with fat saturation andB, axial gradient-echo image. Numerous small and large calcified nodules appear as areas of low signal intensity.

099.qxd 17/6/05 12:56 PM Page 3269

glenoid articular rim disruption. The specific location ofthese lesions is thought to be related to a develop-mentally weak area of the glenoid fossa at an area ofjunction between the ossification centers of the glenoid.These osteochondral lesions are often detected in thethrowing athlete.

Avascular Necrosis

This entity results from a significant decrease or loss ofthe blood supply to the affected region. The mostcommon cause is trauma. Other causes such as steroiduse may be implicated. Avascular necrosis may occurin patients receiving high doses of corticosteroids,though it is only one third as common as femoral headavascular necrosis.438,439 The vessels that supply thehumeral head pierce the bony cortex just distal to theanatomic neck. Fractures proximal to this level, mostcommonly involving the anatomic neck, may result inischemic necrosis of the humeral head (Fig. 99-89). TheMRI findings in osteonecrosis of the shoulder appear asfocal subarticular regions of decreased signal intensity(79%) or as a dark signal intensity band surroundingmore normal marrow fat (21%).440 A double line sign,similar to what has been described in the femoral head,may be seen (Fig. 99-89). Chronic osteonecrosis demon-strates an increase in dark fibrosis-like marrow signal,often complicated by fragmentation and collapse of thearticular surface. Areas of infarction in the diaphysealand metadiaphyseal are completely surrounded by areactive interface and may have a more geographic ordoughnut appearance.440 There are central regions of

high signal intensity representing regions of isolatedmarrow fat, surrounded by bands of low signal intensityrepresenting fibrosis and or calcification in subacuteor chronic infarcts, or a subjacent band of high signalintensity representing reactive granulation tissue in moreacute infarcts.

Quadrilateral Space Syndrome

Another entity whose diagnosis on MRI has beenrecently described is the quadrilateral space syndrome.This refers to impingement of the axillary nerve in thequadrilateral space. This is a space bounded by the teresminor muscle superiorly, the long head of tricepsmedially, the teres major inferiorly, and the surgical neckof the humerus laterally. The posterior humeralcircumflex artery and axillary nerve course here andmay be entrapped by fibrous bands in this region.

Proximal humeral and scapular fractures or axillarymass lesions can result in damage or compression of theaxillary nerve. Injury to the nerve may also occur afteranterior dislocation.Entrapment of this nerve can also beproduced by extreme abduction of the arm duringsleep, hypertrophy of the teres minor muscle inparaplegic patients, or by a fibrous band within thequadrilateral space.441,442 In advanced cases, atrophy ofthe deltoid and teres minor muscles can occur. Aparalabral cyst has been noted as a rare cause ofquadrilateral space syndrome.390

The axillary nerve can be visualized on sagittal obliqueMR images. Osseous lesions involving the axillary nervemay be better seen with plain film radiography or CT.


A B

F I G U R E 99-88

Osteochondral lesion (OCD). A, Axial and B, coronal oblique T2-weighted fast spin-echo MR arthrogram with fatsaturation. Note the osteochondral lesion in the anterior inferior glenoid (arrows). There is a loose body in thesubscapularis bursa (arrowhead in A). The labrum is blunted and torn (thin white arrow in A).

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Soft-tissue lesions can be detected with MRI. Selectiveatrophy or edema of the teres minor muscle and lesscommonly the deltoid caused by axillary nerve com-pression may be identified (Fig. 99-90).443,444

Parsonage-Turner Syndrome

Parsonage-Turner syndrome, also referred to as acutebrachial neuritis, is characterized by the sudden onset ofsevere atraumatic pain in the shoulder girdle.445 Thepain typically decreases spontaneously in 1 to 3 weeksand is followed by weakness of at least one of themuscles about the shoulder. The exact etiology has notbeen established but viral and immunologic causes havebeen considered.

Originally the long thoracic nerve was thought to bemost frequently compromised, but suprascapularnerve disease may be more common. The axillary, radial,

and phrenic nerves may also be affected as well asthe entire brachial plexus. Bilateral involvement maybe present.

MRI findings in the acute stage include diffuseincreased signal intensity on T2-weighted images con-sistent with interstitial muscle edema associated withdenervation (Fig. 99-91). The most commonly affectedmuscles are those innervated by the suprascapularnerve, including the supraspinatus and infraspinatus.The deltoid muscle can also be compromised in cases ofaxillary nerve involvement. Later in the course of thedisease, muscle atrophy manifested by decreased musclebulk may be visualized.239,446

This disorder can resemble a variety of other clinicaldiagnoses, but the most confusing differential diagnosisis compressive neuropathy of the suprascapular nerve.447

MRI can exclude suprascapular nerve entrapmentrelated to paralabral ganglions or other impinging masslesions.239,446,448 Rotator cuff pathology can also bereadily excluded using MRI.


A B

C

F I G U R E 99-89

Avascular necrosis (AVN). A, Coronal T1-weighted image.A focal subarticular region of decreased signal intensityis seen (arrow), reflective of AVN. B, Coronal obliqueT1-weighted image. This patient has a fracture of thehumeral neck (white arrow). A dark signal intensity bandsurrounding more normal marrow fat is seen in thehumeral head (curved black arrow) indicating AVN.C, Sagittal oblique T2-weighted image in the same patientas in B. A double line sign, similar to that described inAVN of the femoral head, is seen (curved black arrow).The displaced humeral neck fracture is again noted (whitearrow). (Courtesy of Charles Hecht-Leavitt MD, VirginiaBeach, VA.)

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A B

A B

F I G U R E 99-90

Quadrilateral space syndrome. A, Coronal short tau inversion recovery (STIR) and B, axial T2-weighted fast spin-echo images. Patient sustained an anterior dislocation. Note the Hill-Sachs lesion in B (black arrow). There isdenervation edema in the deltoid and teres minor muscles (white arrows).

F I G U R E 99-91

Parsonage Turner syndrome. A, Axial short tau inversion recovery (STIR) and B, sagittal oblique T2-weighted images.Increased signal intensity consistent with interstitial muscle edema associated with denervation is seen in thesupraspinatus and infraspinatus muscles (arrows).

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