Acromioclavicular Joint Injuries:Diagnosis and Management

AbstractAcromioclavicular joint injuries represent nearly half of all athleticshoulder injuries, often resulting from a fall onto the tip of theshoulder with the arm in adduction. Stability of this joint dependson the integrity of the acromioclavicular ligaments and capsule aswell as the coracoclavicular ligaments and the trapezius anddeltoid muscles. Along with clinical examination for tenderness andinstability, radiographic examination is critical in the evaluation ofacromioclavicular joint injuries. Nonsurgical treatment is indicatedfor type I and II injuries; surgery is almost always recommended fortype IV, V, and VI injuries. Management of type III injuries remainscontroversial, with nonsurgical treatment favored in most instancesand reconstruction of the acromioclavicular joint reserved forsymptomatic instability. Recommended techniques for stabilizationin cases of acute and late symptomatic instability include screwfixation of the coracoid process to the clavicle, coracoacromialligament transfer, and coracoclavicular ligament reconstruction.Biomechanical studies have demonstrated that anatomicacromioclavicular joint reconstruction is the most effectivetreatment for persistent instability.

Acromioclavicular (AC) joint in-juries represent 40% to 50% ofathletic shoulder injuries.1,2 Thetreatment of AC instability has beenan ongoing source of controversy.Long before a three-grade classifica-tion of the injury was developed byTossy et al3 and Allman4 in the 1960sand then expanded by Rockwood in1989,5 surgeons debated the methodand timing of treatment. The greatestsource of dispute has been the issueof nonsurgical management versussurgical reconstruction for completedislocations.In the mid 1970s, most residency

program directors in the UnitedStates recommended surgical treat-ment for type III dislocations (ie, lossof contact between the clavicle andthe acromion).6 However, by the

early 1990s, 135 of 187 surgeonspreferred nonsurgical treatment(72.2%).7 A series of comparativestudies has supported this trend.8-12

Today, the tendency in managementis toward minimal intervention.13

However, surgical management,most commonly in the form of cora-coclavicular (CC) fixation14 and/orligament reconstruction,15,16 is oftenundertaken after consideration of in-dividual patient demands and injurychronicity.

Joint Anatomy andBiomechanics

The AC joint is a diarthrodial jointformed between the lateral end ofthe clavicle and the medial end of the

Ryan Simovitch, MD

Brett Sanders, MD

Mehmet Ozbaydar, MD

Kyle Lavery, BS

Jon J. P. Warner, MD

Dr. Simovitch is Attending Surgeon,Palm Beach Orthopaedic Institute,Palm Beach Gardens, FL.Dr. Sanders is Attending Surgeon,Center for Sports Medicine andOrthopaedics, Chattanooga, TN.Dr. Ozbaydar is International Fellow,Harvard Shoulder Service,Massachusetts General Hospital,Boston, MA. Mr. Lavery is ResearchAssistant, Harvard Shoulder Service,Massachusetts General Hospital.Dr. Warner is Chief, HarvardShoulder Service, MassachusettsGeneral Hospital.

Dr. Warner or a member of hisimmediate family has receivedroyalties from Zimmer, and researchor institutional support from Aircast(DJ), Arthrex, Mitek, Smith &Nephew, and Zimmer. None of thefollowing authors or a member oftheir immediate families hasreceived anything of value from orowns stock in a commercialcompany or institution relateddirectly or indirectly to the subject ofthis article: Dr. Simovitch,Dr. Sanders, Dr. Ozbaydar, andMr. Lavery.

Reprint requests: Dr. Simovitch,Palm Beach Orthopaedic Institute,Suite 500, 3401 PGA Boulevard,Palm Beach Gardens, FL 33410.

J Am Acad Orthop Surg 2009;17:207-219

Copyright 2009 by the AmericanAcademy of Orthopaedic Surgeons.

Review Article

April 2009, Vol 17, No 4 207

acromion. This joint has a variableinclination between nearly verticaland 50 of obliquity, where the supe-rior edge of the clavicle is more lat-eral. A fibrocartilaginous disk existsat the AC joint and has been shownto involute with age and disintegrateby age 40 years.17 Innervation of theAC joint is from the lateral pectoral,axillary, and suprascapular nerves.Multiple studies have confirmed thatthe clavicle rotates approximately40 to 45 with full shoulder eleva-tion and abduction.18 However, theclavicle actually only rotates approx-imately 5 to 8 relative to the acro-mion because of synchronous scapu-loclavicular (SC) motion.19 This isthe basis for shoulder elevation re-maining normal after CC arthrodesiswith a lag screw.20

The AC joint has both static anddynamic stabilizers (Figure 1). Thestatic stabilizers include the AC jointcapsule as well as the AC ligamentsthat reinforce the capsule. Biome-chanical investigations have foundthat these structures predominantlycontrol horizontal motion of theclavicle.21 Klimkiewicz et al22 demon-

strated in cadaveric specimens thatthe posterosuperior capsule is essen-tial in preventing excessive posteriortranslation of the clavicle and there-fore that excessive distal clavicle ex-cision can result in increased pos-terior clavicle translation.22 Theposterior and superior AC ligamentscontribute most to the horizontalstability of this joint. Authors of arecent cadaveric study demonstratedthat a distal 1 cm clavicle resectionresults in a 32% increase in posteriortranslation compared with the intactstate.23 A resection

complete AC joint dislocation andinstability, AC dislocations can occurin the context of intra- and extra-articular fractures of the base of thecoracoid process. Such an injury isconsidered equivalent to a CC rup-ture. Epiphyseal separation in chil-dren and young adults, as well asdistal clavicle fractures, can result inthe appearance of AC dislocationon radiographs; these are termedpseudodislocations.20

Classification

The degree of injury to the AC jointis dependent on the amount of en-ergy transferred to the acromion andclavicle and their ligamentous stabi-lizers. Tossy et al3 and Allman4 origi-nally classified AC joint injuries intothree grades. This classification sys-tem was subsequently modified byRockwood into six types (Table 1).5

In type I injury, there is no visibledeformity. There may be some swell-ing and tenderness over the AC joint,but there is no tenderness over theCC interspace. Radiographs appearnormal.In type II injury, the distal clavicle

is unstable horizontally and can bedisplaced anteriorly or posteriorly.

Although there may be vertical insta-bility, it is usually absent or minimal.In contrast to type I injuries, there istenderness overlying the CC inter-space. Radiographically, the AC jointis disrupted and may be widened,with a slight vertical displacementand concomitant increase in the CCinterspace.The distal clavicle is unstable verti-

cally and horizontally in type III in-jury. Radiographically, the AC jointis dislocated, with the acromion dis-placed inferiorly relative to the clavi-cle. There is tenderness in the CCinterspace. Pain is typically more se-vere in type III and higher injuries.The AC joint is reducible by an up-ward force placed on the ipsilateralelbow. Certain injury patternsmimic, but should be distinguishedfrom, type III AC injuries. Thesevariants include Salter-Harris injuriesto the distal clavicular physis result-ing from late closure of this physis(in persons aged 18 to 22 years), andAC dislocations associated with in-tact CC ligaments and a fracture ofthe coracoid process.AC joint dislocation with the clavi-

cle displaced posteriorly into orthrough the trapezius muscle identi-fies a type IV injury. Clinically, the

anterior acromion may be promi-nent. Radiographically, the CC inter-space is increased, and posteriortranslation of the lateral clavicle isseen on an axillary lateral view (Fig-ure 2). The AC joint is irreducible onphysical examination. The SC jointand brachial plexus should be evalu-ated in all AC injuries, but such eval-uation is particularly important intype IV injuries, given the reports ofbipolar clavicular dislocations (eg,synchronous AC and SC disloca-tion).In a type V injury, in addition to

disruption of all of the stabilizing lig-aments (as in a type III or IV injury),the deltoid and trapezius musclesand fascia are more extensively de-tached from the clavicle. Clinically,the clavicle lies subcutaneously. Oc-casionally there is so much inferiordisplacement of the upper extremitythat the patient develops symptomsfrom traction on the brachial plexus.The AC joint is irreducible.The rare type VI injury represents

a high-energy variant that usually oc-curs as a result of hyperabductionand external rotation. The distalclavicle typically comes to rest in asubacromial or subcoracoid position(Figure 3). Because this injury is usu-

Table 1Characterization of Acromioclavicular Joint Injuries by the Rockwood Classification*

TypeAC

LigamentsCC

LigamentsDeltopectoral

FasciaRadiographic CCDistance Increase

Radiographic ACAppearance

AC JointReducible

I Sprained Intact Intact Normal (1.1 to1.3 cm)

Normal N/A

II Disrupted Sprained Intact

ally the result of high-energy trauma,it is often accompanied by multiplefractures of the clavicle and ribs.

Subcoracoid displacement may be as-sociated with brachial plexus or vas-cular injury.

Diagnosis

Clinical FindingsInjury to the AC joint should be sus-pected in any patient who has shoul-der trauma with pain in the vicinityof the acromion and clavicle. Duringthe clinical examination, the patientshould be in the standing or sittingposition without support for the in-jured arm. The weight of the armpulling downward often makes thedeformity more apparent.On physical examination, findings

related to the severity of the injury,such as local swelling, deformity,abrasion, or bruising, may be noted.The distal end of the clavicle is some-times displaced enough to tent theskin. With AC injury, local tender-ness is present on palpation over theAC joint as well as in the CC inter-space. AC joint palpation providesguidance related to the degree anddirection of the displacement of theclavicle compared with the acro-mion. The clavicle should also becarefully palpated to detect possiblefractures. Disruption of the deltotra-pezial fascia should be noted ifpresent. Passive and active motion ofthe shoulder produces focal pain atthe injured AC joint. This pain is of-ten accentuated by abduction andcross-body adduction. The OBrienactive compression test for pain overthe AC joint may be helpful.28

The AC joint should next be as-sessed for stability. Evaluation of sta-bility is difficult in the acute phasebecause of patient discomfort andguarding. In the subacute phase, af-ter partial resolution of pain, hori-zontal and vertical instability can bedetected. Because an AC joint injuryoccurs by inferior displacement ofthe scapula, determining whether theAC joint is reducible is done by sta-bilizing the clavicle with one handand placing an upward force underthe ipsilateral elbow with the other

Three-dimensional computed tomography scan demonstrating thesubcoracoid variant of a type VI acromioclavicular dislocation.

Figure 3

A 33-year-old man presented with shoulder pain and an abrasion over thesuperior portion of the shoulder following a fall from a motorcycle.A, Anteroposterior radiograph with a 10 to 15 cephalic tilt demonstrating anincrease in the coracoclavicular interspace distance (*). B, Axillary lateralradiograph demonstrating posterior displacement (posteriorly directed arrow),thereby distinguishing this as a type IV injury. The acromion (A) and theclavicle (C) are outlined.

Figure 2

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hand. A type III AC joint injury canbe differentiated from a type IV or Vjoint injury based on whether the ACjoint dislocation can be reduced (Ta-ble 1). Once the AC joint is reducedwith this maneuver, the examiner cangrasp with the index finger andthumb the midshaft of the clavicleand attempt to translate it anteriorlyand posteriorly to assess horizontalstability.The sternoclavicular joint should al-

ways be examined for an associated an-terior dislocation. The neurologic sta-tus of the affected extremity should beevaluated in all AC injuries to rule outa brachial plexus injury.

Radiographic EvaluationStandardized radiographs are essen-tial to diagnose and classify AC jointinjuries. Routine radiographs for ACjoint evaluation include a true an-teroposterior and an axillary lateralview of the shoulder, as well asZanca views (10 to 15 cephalic tilt)taken with the patient in an uprightposition without support of the in-jured arm. Ideally, comparison viewsof the uninjured shoulder should beobtained to provide normative infor-mation with regard to the CC dis-tance and relative posterior displace-ment of the distal clavicle.Stress views of the AC joint have

been described to differentiate be-tween type II and type III injuries.However, the weighted stress viewsare costly and uncomfortable for thepatient; also, they rarely provide newinformation to help diagnose an un-stable injury. Thus, they are nolonger routinely used.Coracoid process fractures should

always be suspected when radio-graphs reveal AC dislocation in thepresence of a normal CC distance(1.1 to 1.3 cm). When the coracoidfracture is not obvious on the axil-lary view, the Stryker notch view willalmost always demonstrate it.

Treatment

NonsurgicalNonsurgical treatment is uniformlyrecommended for type I and type IIinjuries. Although multiple methodsfor clavicle reduction and immobili-zation have been described, most au-thors suggest a period of immobiliza-tion in a simple sling or shoulderimmobilizer to remove stress fromthe injured CC and/or AC liga-ments.14,29 Generally, type I injuriescan be treated by use of a simplesling for 7 to 10 days or until painsubsides. Type II injuries may requireimmobilization for as long as 2weeks for resolution of symptoms.Once the shoulder pain has subsided,an early and gradual rehabilitationprogram is instituted, with the focuson passive- and active-assisted rangeof motion (ROM). After symmetricand painless shoulder ROM isachieved, an isometric strengtheningprogram is begun. This is followedby isotonic strengthening with agradual escalation of strengtheningand endurance. Contact sports andheavy lifting should be avoided for 2to 3 months to allow for ligamenthealing and avoid converting an in-complete injury to a complete typeIII injury.Most studies support nonsurgical

treatment of type III injuries, al-though this is controversial. Nonsur-gical treatment is well accepted, butmid- and long-term outcomes shouldnot be ignored. Several studies havedemonstrated persistent disability inpatients treated nonsurgically. Berg-feld et al30 evaluated United StatesNaval Academy midshipmen andfound that 30% of patients with typeI and 42% of patients with type IIinjuries reported minor symptomssuch as clicking and pain with push-ups and dips. An additional 9% and23% of patients with type I and IIinjuries, respectively, reported severe

persistent pain and limitation of ac-tivities. Mouhsine et al31 reportedsimilar results. Of patients with typeI and II AC injuries treated nonsurgi-cally, 27% developed chronic ACsymptoms at a mean of 26 monthsafter injury and susequently requiredsurgical intervention. Of the patientswho chose later surgery, a significantproportion had activity-related painand residual anteroposterior instabil-ity.Bannister et al9 conducted a ran-

domized, prospective, controlledtrial comparing acute surgical treat-ment of Rockwood type III and VAC joint dislocations using a CCscrew versus 2 weeks of immobiliza-tion in a sling. The same rehabilita-tion protocol was used in bothgroups. Patients were stratified ac-cording to the severity of AC jointdisplacement. Patients with AC dis-placement

come rates whether managed nonsur-gically or surgically. Patients treatednonsurgically returned to work andpreinjury activities sooner and hadmore nearly normal strength andROM at follow-up. Patients treatedsurgically had a higher complicationrate. However, there was no stan-dardization of surgical techniqueor nonsurgical treatment methodamong the studies reviewed. Wojtysand Nelson33 reviewed 22 patientswith type III AC dislocations. Theydetermined that laborers and athletescan recover adequate strength andendurance with nonsurgical treat-ment of type III injuries despite aslight decrease in both measures.However, they expressed concernthat the decrease in endurance andstrength, despite not being statisti-cally significant, coupled with persis-tent pain and soreness, may be worthconsidering in developing a treat-ment plan for patients who dependon high levels of shoulder strength orendurance for a job or sport. Multi-ple other studies have demonstratedsuccessful short- and mid-term clini-cal outcomes in patients with type IIIinjuries treated nonsurgically.34-36

Proper and adequate rehabilitationmay be critical to successful nonsur-gical treatment of type III AC inju-ries. Glick et al37 evaluated 35 unre-

duced AC dislocations that weretreated nonsurgically in a profes-sional and competitive recreationalathletic population. None of the pa-tients was disabled. In addition, noneof the patients who had a supervisedrehabilitation program had reportsof pain. These authors concludedthat the predominant reason for per-sistent pain and disability after atype III AC injury treated nonsurgi-cally was inadequate rehabilitation.This conclusion is supported by theassertion by Gurd38 that the shouldercan function normally despite an ab-sent clavicle as long as the shouldergirdle muscles are strengthened andmaintained. Thus, a structured activerehabilitation program that focuseson gaining strength of shoulder gir-dle muscles, including the deltoid,trapezius, sternocleidomastoid, andsubclavius, as well as the rotator cuffand periscapular stabilizers, is indi-cated for patients who are treatednonsurgically.Although there is no conclusive ev-

idence of it in the literature, a rela-tive indication for AC surgical stabi-lization after an acute type III injurymay be young age or a job or sportthat places high demands on theshoulder. In addition, chronic symp-toms of instability and pain follow-ing a type III AC dislocation may

warrant delayed surgical reconstruc-tion. Recent reports of successfulnonsurgical treatment of type III ACinjuries in professional baseball play-ers have challenged the relative in-dication of sport or job type in se-lecting a management protocol.39

Despite the success of nonsurgicaltreatment, late symptomatic sequelaecan develop. Occasionally, distalclavicle osteolysis or a painful ACdisk injury, akin to a knee meniscaltear, occurs acutely, or AC arthritisdevelops over time. When sympto-matic, these conditions can betreated by steroid injection or distalclavicle resection with intra-articulardisk excision, as described by Mum-ford,40 combined with a ligamentousreconstruction to establish stability.

SurgicalThe case can be made for surgicalmanagement of some acute type IIIAC joint dislocations. However,acute type IV, V, and VI AC joint dis-locations all require surgical inter-vention, although there is no consen-sus on which technique to use.Surgical techniques can be catego-rized into three main groups (Table2), although all have the goal of ob-taining and retaining anatomic ACjoint reduction.

Table 2Surgical Techniques for the Management of Acromioclavicular Joint Dislocation

Technique Method Features

Primary acromioclavicular jointfixation

Kirschner wires, hook-plate Limited dissectionRisk of pin migrationReserved for acute injury

Fixation between the coracoidprocess and clavicle

CC screw, suture loop Screw requires staged removalSuture loop can be inserted arthroscopicallyReserved for acute injuriesSuture loop can cut through the clavicle or coracoid base

Dynamic muscle transfer Coracoid transfer Abandoned due to inferior long-term resultsLigament reconstruction Autogenous hamstring, anterior

tibialis allograft, CA ligamenttransfer

Attempts to anatomically reestablish CC ligament anatomyProvides biologic scaffold for revascularizationAppropriate for acute and chronic reconstructions

CA = coracoacromial, CC = coracoclavicular

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Primary Fixation of theAcromioclavicular JointHistorically, primary fixation of theAC joint consisted of pin fixation us-ing either smooth or threadedKirschner wires after a closed oropen reduction. However, thismethod has been abandoned, giventhe rare but catastrophic occurrenceof pin migration; the pins have beenfound in the heart, lungs, and greatvessels.41,42

An alternative technique com-monly used in Europe is the hook-plate. After open reduction of theAC joint, the lateral end of the plateis inserted deep to the acromion andlevered down on the clavicle to re-duce the joint. It is secured to theclavicle with bicortical screws. Somesurgeons combine hook-plate fixa-tion with ligament reconstruction,43

while others use the hook-platealone.44 The plate is removed at 8weeks. This technique has been suc-cessful in treating AC dislocationsand distal clavicle fractures.43 Sim etal,44 however, reported that 8 of 16patients experienced complications(one bent plate, one plate disloca-tion, six infections).

Fixation Between the CoracoidProcess and ClavicleBosworth45 popularized the use of ascrew for CC fixation. The use ofscrews and suture loops has been de-scribed alone and in combinationwith ligament reconstruction. Rock-wood et al20 recommended that a CCscrew (Figure 4) be combined withligament reconstruction in acutecases of AC dislocation. Through re-cent arthroscopic advances, CC fixa-tion can now be accomplished byless invasive means.Placement of synthetic loops be-

tween the coracoid process and clavi-cle have been described by severalauthors, most often in combinationwith a form of CC ligament recon-struction. The main advantage of

this technique is that it does not re-quire staged removal as do CCscrews. Absorbable and nonabsorb-able materials can be used. Morrisonand Lemos46 demonstrated the im-portance of accurate positioning of asynthetic loop to allow for the mostanatomic reduction possible. Poten-tial complications of this techniqueinclude suture cutout. Good resultshave been reported with 6-mm poly-tetrafluoroethylene surgical tape as asecondary fixation combined withcoracoacromial (CA) ligament trans-fer.46 However, cases of asepticforeign-body reaction and clavicleosteolysis that resulted in failurehave been reported.47,48

Coracoid Process TransferTransfer of the coracoid process wasfirst described by Dewar and Bar-rington.49 It has been used for thetreatment of acute and chronic inju-ries, with better results in youngerpatients. However, reports of resid-ual joint aching led to the proce-

dures being abandoned because ofpoor long-term outcomes.50

Ligament ReconstructionWeaver and Dunn15 first describedthe use of the native CA ligament toreestablish AC joint stability (Figure5). This technique has since beenmodified to include resection of thedistal clavicle to avoid late degenera-tive changes at the AC joint. The CAligament is detached from the deepsurface of the acromion with orwithout a chip of bone and is thentransferred to the clavicle. This con-struct can be augmented with a su-ture loop that provides protectionwhile the reconstructed ligamentheals. Recently, Lafosse et al51 de-scribed an all-arthroscopic techniquefor CA ligament transfer in the set-ting of acute or chronic AC disloca-tions.An alternative technique for liga-

ment reconstruction is the use of asemitendinosus tendon autograft.This technique is combined with re-

A, Intraoperative photograph demonstrating percutaneous placement of acoracoclavicular (CC) screw under fluoroscopic guidance. The screw isplaced to reduce the CC interspace and anchor the clavicle to the coracoidprocess during soft-tissue healing, as demonstrated in an intraoperativeanteroposterior radiograph (B).

Figure 4

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section of the distal clavicle. Joneset al52 described the use of a loopedsemitendinosus graft around thecoracoid process and clavicle in a re-vision AC joint reconstruction. Maz-zocca et al16 modified this technique,incorporating a doubled semitendi-nosus graft inserted in a coracoidbone tunnel and secured in two sepa-rate clavicle bone tunnels. Interfer-ence screws were used to approxi-mate the anatomic location of thetrapezoid ligaments. Biomechanicaltesting of this construct has been fa-vorable. We have used anterior tibia-lis tendon allograft in reconstruction(Figure 6). Good clinical results havebeen achieved using hamstring ten-dons to reconstruct high-grade ACseparations.53 However, future stud-ies must examine the extent to whichtwo drill holes weaken the clavicleand how tunnel expansion54 influ-ences the biomechanical and clinicaloutcomes of this treatment.We favor the use of a doubled

semitendinosus autograft or tibialisanterior allograft looped around the

The modified Weaver-Dunn procedure. The coracoacromial ligament (A) istransferred to the clavicle to substitute for the ruptured coracoclavicularligaments. A suture loop (B) can be used for augmentation.

Figure 5

Intraoperative photographs of a procedure to anatomically reconstruct the coracoclavicular ligaments through bonetunnels in the clavicle (C) using a semitendinosus allograft. A, A suture passer is passed from medial to lateral aroundthe coracoid tip (*) and used to retrieve the anterior tibialis allograft around the coracoid process. B, The graft ends arepulled through two bone tunnels (arrows) in the clavicle to approximate the pull of the conoid and trapezoid ligaments.

Figure 6

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coracoid process or potted in a cora-coid bone socket. The graft is fixedwith interference screws through twoseparate clavicle bone tunnels thatapproximate the normal anatomiclocation and orientation of the CCligaments. We believe that this bestreplicates the injured anatomy. Bio-mechanical studies have demon-strated the superiority of this con-struct. We routinely resect the distalclavicle at the index operation. How-ever, recent interest in the additionalAC stability conferred by not resectingthe distal clavicle and the clinical ram-ifications of doing so may be compel-ling. A possible shift in the treatmentparadigm awaits further prospectiveclinical and well-designed biomechan-ical trials.

Distal Clavicle ResectionThere has been some interest in pri-mary or delayed excision of the dis-tal clavicle (ie, Mumford procedure)in a symptomatic AC joint after dis-location. Although there has beensuccess with this technique doneopen as well as arthroscopically, itmust be reserved for patients inwhom the CC ligaments are intactand there is no concomitant instabil-ity. When horizontal or vertical in-stability exists, results are compro-mised because this technique doesnot address instability and may ac-centuate it.23,24,55

BiomechanicalConsiderations

The goal of AC joint reconstruction,when indicated, is to achieve an ana-tomic reconstruction that best re-stores both the restraint to vertical aswell as anteroposterior translation ofthe clavicle at the AC joint. Multiplestudies have examined the biome-chanical results of various recon-structive techniques (Table 3), andseveral conclusions can be drawn

from them.16,56-63 A study by Jariet al56 suggests that surgical tech-niques that preserve the articulatingsurface of the clavicle at the AC jointlead to lower joint contact forces andare preferred.CA ligament transfer, which has

long been the most popular methodfor treating complete chronic AC dis-locations, has just 25% of thestrength of the intact CC complexand allows far greater primary andcoupled translation than does the in-tact AC joint.63 Augmentation of thisrepair/reconstruction with varioussuture loops and suture anchors canincrease the construct strength andultimate load to failure while reduc-ing primary and coupled translation.However, these constructs are biome-chanically inferior to the native in-tact AC and CC capsuloligamentousunit. Screw fixation may also be con-sidered. Although the bicorticalRockwood screw has the highest ten-sile strength and stiffness with thelowest elasticity, these propertiesmay also be responsible for its highcomplication rate, including screwbreakage and pullout.56

In a recent study of 42 cadaveric spec-imens, Mazzocca et al16 compared thestability conferred by three AC joint re-construction techniques: CA ligamenttransfer and distal clavicle resectionwith suture loop augmentation, ana-tomic reconstruction with a double-bundled semitendinosus graft insertedinto a coracoid bone socket, and ar-throscopic reconstruction with sutureand titanium screws (ie, suture loopand CC screw fixation). Only the an-atomic CC reconstruction with tendongraft and suture augmentation pro-vided anterior, posterior, and superiorstability not statistically different fromthe intact state. The authors also rec-ognized that a graft offers the advan-tage of a scaffold for revascularizationcompared with the arthroscopic sutureloop, which does not and which can fa-

tigue and fail over time with cyclicloading.Costic et al57 demonstrated that the

dislocated clavicle can lose up to40% of its stiffness, which suggeststhat previous biomechanical modelsmay be flawed, depending on howthe clavicle and scapula were pottedfor testing.

Complications

Complications can occur as a result ofnonsurgical and surgical treatment ofAC joint dislocations. The most com-mon complications associated withnonsurgical treatment are developmentof late arthrosis and persistent instabil-ity. Distal clavicle osteolysis also hasbeen described.Complications following surgical

treatment of AC joint dislocations arerelated to the technique chosen. Hard-ware failure and migration resulting ininjury to the great vessels have been de-scribed. In addition, aseptic foreign-body reaction or infection may occurafter the use of implants and syntheticsuture. Depending on the choice oftechnique for surgical reconstruction,early or late fracture of the coracoidprocess or clavicle has been reported.In addition, any technique that passesa graft or synthetic material medial tothe coracoid process poses a potentialrisk to the brachial plexus and axillaryartery. Although reconstructive successis clinically predicated on alleviatingpain and establishing AC stability, per-sistent pain and recurrent instabilityhave been reported with all of the de-scribed techniques.

PostoperativeRehabilitation

After CC fixation with a metallicscrew or suture construct for acuteAC injuries, the shoulder is immobi-lized in a simple sling and cold ther-apy device. At 2 weeks, active and

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Table 3Biomechanical Comparison of Acromioclavicular Joint Reconstruction Techniques

Study Methodology Results

Mazzoccaet al16

Biomechanical testing of 42 cadav-eric shoulders for vertical and APtranslation of the AC joint afterthree reconstructive techniques:modified Weaver-Dunn proce-dure, arthroscopic suture fixation,and anatomic CC reconstructionwith semitendinosus graft

All three techniques establish comparable vertical stability and load to failureAnatomic CC reconstruction that reconstructs both conoid and trapezoid liga-

ments allows the least AP translation of the three techniques and best ap-proximates the intact state

Jari et al56 Biomechanical comparison of theCA ligament transfer, CC sling,and Rockwood screw

Compared with the intact AC joint state, anterior, posterior, and superior trans-lation increased 110%, 100%, and 360%, respectively, after the CA ligamenttransfer. With the CC sling, anterior translation increased by 110% and poste-rior translation by 330%.

Primary translation was reduced with the Rockwood screw. A significant de-crease in posterior translation was noted (60%) compared with the intactjoint. Similar findings were noted for coupled translations (ie, AP).

The Rockwood screw was the most rigid construct and was found to experi-ence forces 30% and 170% greater than the intact AC joint in response toanterior and posterior loads, respectively.

Costic et al57 Biomechanical comparison of anintact AC joint with anatomic re-construction using a semitendi-nosus graft

Stiffness and ultimate load to failure of the intact CC ligament state was signifi-cantly greater than for the anatomic reconstruction complex (P 0.05)

Stiffness of the anatomic reconstruction complex (23.4 N/mm) was 40% of thestiffness of the intact CC complex (60.8 N/mm)

Anatomic reconstruction complex had clinically insignificant elongation (

passive ROM is initiated and re-stricted to beneath the shoulder level.Doing so allows the patient to beginactivities of daily living while avoid-ing lifting anything heavier than 5pounds. Once the screw is removedat 2 to 3 months, full active andpassive ROM is encouraged, withstrengthening limited to light resis-tance for 6 to 8 weeks. Once fullROM and strength are obtained, re-turn to athletic competition is per-mitted.After AC joint reconstructionwith an

autogenous or allograft ligament recon-struction (eg, semitendinosus graft,modified Weaver-Dunn), the arm ismaintained in a simple sling. At 2weeks, pendulum exercises are initiated,followed by light activities of daily liv-ing at 4 weeks. With further graft mat-uration at approximately 8 weeks, ac-tive and passive ROM is encouragedwith a therapist, and light resistance canbe initiated after 3 months. Once fullROMand strength are obtained, returnto athletic competition ormanual laboris permitted.

Summary

Significant recent advances havebeen made in the approach to AC

joint injury. There is a consensus thattype I and II AC joint injuries shouldbe treated nonsurgically, while acutetype IV, V, and VI injuries should betreated surgically. The correct algo-rithm for treating type III injuries isnot known; most studies do notshow a significant difference in theclinical outcome between nonsurgi-cally and surgically treated patients.Although it has not been sufficientlydemonstrated, it may be that a sub-set of overhead athletes and heavylaborers would benefit from surgicalreconstruction of type III injuries.The idea that adequate rehabilitationis critical to a successful outcome ofnonsurgical treatment of a type IIIinjury is worthy of attention and fur-ther study. It is often the case thatnonsurgical care translates into be-nign neglect, and perhaps inadequaterehabilitation has been responsiblefor some of the failures related tononsurgical treatment.

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Table 3 (continued)Biomechanical Comparison of Acromioclavicular Joint Reconstruction Techniques

Study Methodology Results

Breslow et al61 Biomechanical comparison of su-ture and suture anchors for theloop method of stabilizing thedislocated AC joint

After 10,000 cycles, laxity of the construct with suture loop was 1.32 0.59mm compared with 1.33 0.94 mm for the suture anchor loop. The differ-ences were not statistically significant.

Harris et al62 Biomechanical comparison of ten-sile strength, tensile stiffness,and elongation at failure with fivetechniques in 19 cadavericshoulders: CA transfer, CC slingwith 8-mm polyester vascularprosthesis, 2 CC suture anchors,unicortical Bosworth screw, andbicortical Bosworth screw

CA ligament transfer demonstrated the weakest reconstruction initiallyCC slings had high tensile strength but were very elastic and had the highest

elongation at failure.CC screws provided the highest tensile strength and stiffness as well as least

elasticity, but only with bicortical coracoid purchase

AC = acromioclavicular, AP = anteroposterior, CA = coracoacromial, CC = coracoclavicular

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