Skeletal Radiol (1990) 19:109-111

Skeletal Radiology

Magnetic resonance imaging in acute and chronic rotator cuff tears

Graham Buirski, M.B., B.S., M.R.C.P., F.R.C.R.

Department of Radiology, Royal Melbourne Hospital, Melbourne, Australia

Abstract. Magnetic resonance imaging has been assessed in patients with acute rotator cuff tears and normal ra- diographs (9 cases) and those with chronic tears and changes of cuff arthropathy (9 cases). All images were obtained using a low field strength system ( F O N A R 0.3 T). Particular attention was placed on the appear- ances of the tendon and the cuff muscles themselves. Six complete acute tears were clearly identified, but MRI failed to demonstrate two partial tears. Muscle bulk was preserved in all patients in this group. In contrast, all patients with cuff arthropathy had complete tears of the supraspinatus tendon with marked tendon retraction and associated muscle atrophy: these changes precluded primary surgical repair. MRI should be used to assess muscle atrophy preoperatively in those patients with acute tears. When plain radiographs demonstrate cuff arthropathy, the MRI appearances are predictable and primary repair is unlikely to be successful. Further imag- ing is therefore not indicated.

Key words: Magnetic resonance imaging - Acute and chronic rotator cuff tears

Address reprint requests to: Graham Buirski, Department of Radi- ology, Royal Melbourne Hospital, Melbourne, Australia, 3050

Magnetic resonance imaging is proving to be an accurate imaging technique for the assessment of the rotator cuff using both high field [2] and low field strength magnets [1, 4]. Authors have drawn attention to the M R appear- ances of the rotator cuff tendons themselves but little regard has been paid to the cuff muscles proximal to the tendon. In addition, few patients with established chronic rotator cuff insufficiency with associated sec- ondary changes of "cuf f a r thropathy" have been as- sessed. This study was undertaken to compare the rota- tor cuff appearances in patients with both acute and chronic cuff tears with particular reference to the mus- cles as well as the tendons.

Patients and methods

Healthy volunteers were initially studied to obtain the appropriate pulse sequences and surface coil. All studies were performed with the subject in the anatomical position previously described in a normal population group [3].

All scans were performed on a Fonar 0.3 resistive magnet at this institution. Following an axial scout image, the scan positions used are shown diagrammatically in Fig. 1 with both Tl-weighted (TE 28 ms/TR 500 ms with 4 averages) and T2-weighted (TE 56 ms/TR 1500 ms with 2 averages) sequences used as indicated.

Humeral head

Scapula Coronal Coaxial

[~ Qnd T2_ T2. T2.

Fig. 1. Diagrammatic representation of the scan positions used for each sequence to assess the rotator cuff tendons and muscles

�9 1990 International Skeletal Society

110 G. Buirski: MRI in rotator cuff tears

Fig. 2. Double-contrast arthrogram of the right shoulder showing a complete acute tear (arrow) through the supraspinatus tendon (St). Contrast medium is seen extending above the tendon (arrowheads)

Fig. 3, Chronic rotator cuff tear. Double contrast arthrogram demonstrates superior subluxation of the humeral head and loss of congruity of the gleno-humeral joint (arrowheads), Subsequent excavation of the inferior surface of the acromion has occurred (arrow) leading to typical changes of cuff arthropathy. Note the complete absence of soft tissue structures interposed between the humeral head and the acromion

Slice thickness was 5 mm with a 2 mm intervening gap. Field of view was 25 cm and matrix size was 256 x 256. A ring receiving surface coil (diameter 16.5 cm) was placed around the axilla and shoulder to obtain the images. A total of 18 patients were exam- ined, separated into two groups:

Group 1. (9 patients). Partial (3) or complete (6) supraspinatus tears were confirmed by double contrast arthrography (Fig. 2). Plain radiographs in this group were entirely normal.

Group 2. (9 patients). All patients had evidence of "cuff arthropa- thy" on the preliminary radiographs characterised by superior sub-

Fig. 4A. Parallel T2 scan (TE 56 ms/TR 1500 ms) through the same shoulder as in Fig. l. The area of high signal (arrow) in the tendon corresponds precisely to the site of tear on the arthrogram. Note that there is tendon still lying between the humeral head and acromion. (Key: St= Supraspinatus tendon; G=Glenoid ; H = Humeral head; A = Acromion) B A coaxial T2 scan (TE 56 ms/TR 1500 ms) through the cuff muscles fails to show any evidence of atrophy. (Key: S = Supraspinatus; ~ = Infraspinatus ; T = Teres major; Su=Subscapularis; Sp -- Scapular spine; Sb = Scapular blade)

Fig. 5A, Parallel T2 MR scan (TE 56 ms/ TR 1500 ms) through the same shoulder as in Fig, 2. The superior subluxation of the humeral head is clearly demonstrated and the supraspinatus tendon is completely ruptured and retracted medially (see key in Fig. 4A) B Marked atrophy of both supraspinatus and infraspinatus muscles is shown on this coaxial T2 scan (TE 56 ms/TR 1500 ms). The remaining cuff muscles are normal (see key in Fig. 4 B)

luxation of the humeral head with concavity and sclerosis on the inferior surface of the acromion. Arthrograms were available in seven patients showing complete supraspinatus tears with attenua- tion of the tendon (Fig. 3).

Results

T h e s u p r a s p i n a t u s t e n d o n was m o s t c lear ly iden t i f i ed in the pa ra l l e l s e q u e n c e (Fig . 1). O c c a s i o n a l l y , c o r o n a l scans s h o w e d the t e n d o n to be t t e r a d v a n t a g e . N o j o i n t

G. Buirski: MRI in rotator cuff tears 11

effusion or any other pathology was demonstrated in any patient.

Group 1

Age range was 44-66 years and the male to female ratio was 8 : 1. Low intensity soft tissue structures were inter- posed between the superior aspect of the humeral head and the inferior surface of the acromion. The supraspin- atus tendon could be clearly identified, but other adja- cent structures (capsule, synovium, and subacromial bursa) could not be differentiated.

A focal area of high signal was seen in the supraspin- atus tendon in six patients particularly on the T2- weighted images (Fig. 4A). In two patients with partial tears, the tendon appeared normal, while in the last case the tendon contained multiple areas of high signal.

The coaxial scans through the rotator cuff muscles themselves, showed that all muscles were normal with no evidence of excessive fatty replacement of the normal muscle fibres (Fig. 4 B).

Group 2

Age range was 47-59 years and the male to female ratio was 7:1. Normal soft tissue structures between the supe- rior surface of the humeral head and the inferior surface of the acromion were absent. This was always associated with slight superior subluxation of the humeral head in keeping with the plain radiographic findings.

Similar findings were seen in all patients. The su- praspinatus tendon was completely ruptured and could not be identified in its normal position. The musculoten- dinous junction and proximal portion of the tendon were retracted medially from the margin of the glenoid la- brum (Fig. 5 A). There was no significant increase in sig- nal intensity from the tendon on T2-weighted images.

Coaxial scans through the rotator cuff muscles of the scapula showed varying degrees of fatty replacement presumed to represent atrophy of the supraspinatus and, to a lesser extent, the infraspinatus muscles (Fig. 5 B). In one patient, marked atrophy of the subscapularis muscle was also noted.

Discussion

The accurate identification of acute rotator cuff tears by a low field strength system [4] is supported in this study where six of the nine patients were abnormal. However, two patients with partial tears at arthrography had normal MRI findings in this study. Seeger et al. [4] have also failed to detect partial tears and this there- fore may be a potential pitfall in the use of the low field strength system. In one patient in group I a diffuse abnormality was seen throughout the tendon sheath: this probably represented widespread haemorrhage and degeneration within the tendon.

Patients with chronic rotator cuff tears and cuff ar- thropathy (group 2) have not been previously assessed using MRI. All have characteristic findings: humeral heads are superiorly subluxated secondary to marked tendon retraction and there is significant muscle atrophy of the supraspinatus and to a lesser extent other cuff muscles. The degree of tendon retraction appears greater on the MR images when compared to the arthrogram. Seeger et al. [4] quote a similar example of a patient with a complete tear but the plain radiographic findings in the patients studied were not discussed and scanning, particularly for muscle bulk, was not part of their proto- col.

The presence of muscle atrophy and tendon retrac- tion are of surgical importance: three patients underwent surgery for primary repair of the tendon, but this was not possible due to the retraction and atrophy. In none of these group 2 patients was atrophy demonstrated clin- ically. Conservative treatment, such as physiotherapy, might also be unrewarding in these cases.

Although numbers in this study are small, it appears that in patients with cuff arthropathy, not only are the arthrographic findings of the cuff mechanism predictable but so are the MRI appearances. Once arthropathic changes have occurred, further investigation and imag- ing would seem unnecessary as primary repair will not be possible. Undoubtedly, there will be some patients in whom cuff tears are chronic with associated atrophy but where radiographic changes of cuff ar thropathy have not yet developed. In these cases MR imaging of the muscles should be performed prior to definitive treat- ment. Prospective clinical studies are still required to determine the importance of atrophy in these latter cases.

Patients in whom plain radiographs are normal will require imaging of the rotator cuff in order to exclude tears from other causes of impingement syndrome [4]. Ideally, MRI should be the primary investigation of choice [2] but when there is lack of accessibility to scan- ners or if MRI is normal (e.g., in some partial tears) then arthrography will still be required. MRI should follow arthrography in (a) the preoperative assessment of tendon position and muscle atrophy and (b) to ex- clude intrasubstance tears when the arthrogram is nor- mal.

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cuff impingement syndrome: MR imaging. Radiology 166 : 211 2. Kneeland JB, Middleton WD, Carrera GF, Zeuge RC, Jesman-

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3. Seeger LL, Ruszkowski JT, Basset LW, Kay SP, Kahmann RD, Ellman H (1987) MR imaging of the normal shoulder: Anatomic correlation. AJR 148 : 83

4. Seeger LL, Gold RH, Bassett LW, Ellman H (1988) Shoulder impingment syndrome - MR findings in 53 shoulders. AJR 150: 343