Shoulder Resources

Acromioclavicular and sternoclavicular injuries (R)(M) Acromioclavicular and sternoclavicular injuries (R)(M)


Anatomy
The AC joint is lined by hyaline cartilage with a fibrocartilage articular disc, which degenerates early in life. The acromial part of the joint is convex and the clavicular part is concave. The acromioclavicular joint is stabilized by the acromioclavicular capsular ligaments (which act as primary restraints to posterior movement) and the coraco-clavicular ligaments which act as the primary restraint to superior and anterior motion. The superior part of the AC ligament is stronger than the inferior. The conoid ligament is stronger than the trapezoid ligament. Motion at the AC joint is only around 5-8 degrees. Acromioclavicular joint disruption.

Aetiology
Fall onto point of shoulder. The clavicle rests on the first rib which prevents downwards displacement of the clavicle but allows separation of the acromion.

Imaging
The AC joint can be highlighted by taking the shot with a 10-degree cephalad tilt and using 50% of the voltage of a standard radiograph because of the paucity of soft tissue covering the region.

Classification (Rockwood)
Type I Sprain of joint capsule
Type II Disruption of joint capsule with preservation of coraco-clavicular ligs. This results in anteroposterior instability.
Type III Disruption of joint capsule and coraco-clavicular ligaments
Type IV Posterior displacement of clavicle through trapezius
Type V Complete disruption of soft tissue from clavicle with displacement of the clavicle more than 2 widths superiorly
Type VI Subcoracoid displacement of the clavicle

Treatment
Types I and II: observe
Types IV, V and VI: repair. Multiple methods using Bosworth screws, mersilene tape
Type III: controversial.
Report on natural history of type III dislocations in AJSM showed that 80% of Type III dislocations were satisfied with a non-operative course. A distinct advantage of surgical over nonsurgical treatment has never been demonstrated. A recent meta-analysis showed patient satisfaction in 88% of surgically treated lesions and 87% of non-surgically treated. Pain, ROM and strength were all similar. Wound or skin breakdown in 6% of surgically treated cases vs. only 1% of nonsurgically treated cases; however deformity in 3% of surgically treated cases vs. 37% of nonsurgically treated cases.

Significantly longer return to work in surgically treated cases. Should probably fix in labourers, athletes and other high demand patients. At the Campbell clinic all Grade III injuries are treated nonoperatively with late reconstruction if necessary. (10th Ed.) Chronic injuries may require transfer of CA ligament into the medullary canal of the resected end of the distal clavicle (modified Weaver-Dunn procedure). This is supported by a coracoclavicular suture.

Acromioclavicular arthritis
Radiographic changes of primary ACJ arthritis occur in around 50% of patients, but most are asymptomatic. Symptomatic posttraumatic ACJ arthritis is more common, and seen in 8-42% of patients with Gd II – III ACJ disruption. Presents with localized tenderness, pain with crossed body adduction and positive O'Brien test. Pain at the end of abduction is also a sign of AC arthritis. Impingement symptoms are also common as the osteophytes narrow the subacromial space. Imaging demonstrates joint space narrowing and osteophytes. The normal joint in young patients is around 2-3mm wide, but by the age of 60 may only be 0.5mm wide. MRI is very sensitive, but very nonspecific with around 75% of all asymptomatic volunteers having evidence of arthritis on MRI scans.

Diagnosis may be confirmed with injection of local anaesthetic into joint. A further injection into the subacromial space may help to diagnose co-existing RC pathology. Treatment is with local anaesthetic and steroid injections. Activity modification is also beneficial; sometimes just changing the width of grip when doing bench presses and avoiding pushups may be enough. If these fail, the operative approach is resection of the distal clavicle, either open or arthroscopically. Gurd and Mumford first reported on resection of the distal clavicle. The arthroscopic resection may be indirect, via the subacromial space, or direct, via instruments introduced directly into the joint – this may be particularly useful in cases of osteolysis where the joint space is widened. The amount that should be resected is controversial, but the average figure is around 1cm.

The arm should be placed in a position of cross body adduction at the end of the procedure to ensure there is no abutment. Some authorities feel that abutment can be avoided with as little as 4mm of resection. The results are good to excellent in 62-100% of open procedures and 83-100% arthroscopic procedures. The return to work is sooner in arthroscopic patients. Complications of resection include persistent pain, either through misdiagnosis or inadequate resection, and instability of the ACJ. Instability may be less after arthroscopic debridement as the superior ACJ ligaments are not violated; this decreases the risk of posterior instability. Note: there is a very high rate of co-existing glenohumeral pathology – an arthroscopic study found 213 of 218 patients with a painful AC joint had concomitant pathologic lesions in the shoulder.

Distal clavicle osteolysis
This is common in weight lifters. Consists of osteopenia and cystic changes in distal clavicle, in response to the high compressive loads that are generated across the AC joint. There is often widening of the ACJ, of more than 5-6mm. Often responds to activity modification. Occasionally requires distal clavicle resection.

Sternoclavicular instability
This is classified as anterior or posterior. Patients with anterior dislocation present with a palpable clavicular head, that becomes more prominent as the arm is abducted and elevated. Posterior dislocations have a hollow lateral to the sternum, and may be associated with dysphagia, dyspnoea and upper extremity paraesthesias. XR taken with 40 degrees of cephalic tilt (serendipity view) may better show the direction of displacement. The lesion is seen best with CT scanning. Treatment may include an attempt at closed reduction through traction on the extended arm. If this fails, an anterior dislocation should be accepted. A posterior dislocation may need ORIF; one can try using towel clip forceps first. Most dislocations are stable after reduction, but if not nonabsorbable sutures should be used. Consider having a cardiothoracic surgeon present in the theatre for posterior dislocations.

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