Case Vignette

Is It The Shoulder Joint Or The Acromioclavicular Joint?

The shoulder joint is formed by the upper end of the arm bone (the humerus) and a socket (the glenoid) on the outer edge of the shoulder blade (the scapula). It is the humeral head which articulates with the glenoid process.


The acromioclavicular joint is nearby, but separate. It is formed by the outer end of the collar bone (the clavicle) and the inner aspect of the acromion (part of the shoulder blade but well above the socket).


So What is the Issue Here?

The shoulder girdle itself works synchronously but the two joints do remain separate. The acromioclavicular joint not uncommonly develops degenerative changes as patients age.

Plaintiffs can be injured and sustain ongoing problems referable to the shoulder joint or glenohumeral joint itself. This may involve the rotator cuff, the labrum around the glenoid, the glenoid itself or even the humeral head. Specific therapeutic regimens may be required, functional losses may result and compensation could be due.

It should be appreciated however that the acromioclavicular joint is not necessarily involved in the process.

It is the Operative Loss

During the course of an operative management programme for the glenohumeral or shoulder joint, some upper limb surgeons will also ablate the acromioclavicular joint by removing the outer end of the clavicle.

That supplemental procedure (the acromioclavicular joint excision) is not necessarily linked with the original injury and is therefore not of a compensable nature. The AMA 5 Guides however ascribe some considerable importance to the acromioclavicular joint. The excision of the outer end of the clavicle, thereby ablating the acromioclavicular joint, yields a loss of 10% of upper extremity function or a loss of 6% of whole person function. You could refer to Table 16-27 on page 506 and Table 16-3 on page 439 to check my calculations.

This is a significant impairment but it is not necessarily due to the subject accident. Apportionment of blame will be necessary.