The diagnosis and treatment of anterior instability in the throwing athlete

Abstract

In the overhand or throwing athlete, the shoulder is extremely vulnerable to injury due to the repetitive, high-energy forces. When these stresses are applied at a rate that exceeds that of tissue repair, progressive damage to the shoulder's stabilizing structures can occur. With continued throwing, the static restraints become progressively attenuated, allowing anterior glenohumeral subluxation. Initially, the dynamic stabilizers can compensate for this mild instability with increased muscle activity. Prolonged activity, however, may lead to fatigue. Over time, these compensatory mechanisms can become overloaded. The humeral head then may subluxate anteriorly, where it contacts with the coracoacromial arch, ultimately leading to subacromial impingement. Posterosuperior glenoid impingement may also occur as anterior humeral translation allows the undersurface of the tendinous portions of the supraspinatus and infraspinatus to impinge along the posterosuperior border of the glenoid rim. Fortunately, conservative management is effective in most chronic overuse injuries and includes an initial period of relative rest (avoidance of throwing), oral nonsteroidal antiinflammatory medication, a physical therapy program structured to provide local modalities to reduce inflammation, and a strengthening program for the rotator cuff and scapular rotators. For those athletes with continued symptoms, surgical intervention may become necessary. The appropriate surgical treatment depends on the diagnosis. In the young throwing athlete with shoulder pain, it is essential to recognize that instability or occult subluxation, rather than impingement, is the primary underlying pathology. The anterior capsulolabral reconstruction addresses the problem of instability by correcting the capsular redundancy or labral damage or both. When performed in the manner described, muscle attachments and proprioceptive muscle fibers are not disturbed and full shoulder range of motion can quickly be achieved. This most recent surgical technique and postoperative rehabilitation program has resulted in a significant improvement in the ability to correct instability in those athletes who have failed a prolonged course of conservative care. Prevention of these injuries may be attained, it is hoped, through continued research into the basic biomechanics and the pathoanatomy associated with overhand sports. In addition, further modifications of existing surgical techniques and refinement of rehabilitation programs may continue to more predictably and successfully return these athletes to their prior competitive level.