Role of the coracoacromial ligament as restraint after shoulder hemiarthroplasty.

Patients with an irreparable rotator cuff tear and glenohumeral degeneration often are treated with hemiarthroplasty. This procedure has proven effective as long as the coracoacromial ligament remained intact. The ligament reportedly acts as a restraint against anterosuperior dislocation. The purpose of the current study was to test the role of the coracoacromial ligament as an anterosuperior restraint after hemiarthroplasty in shoulders from cadavers with simulated irreparable rotator cuff tears. Six fresh-frozen shoulders were dissected to mimic a massive rotator cuff tear. After a hemiarthroplasty was done, each shoulder was mounted in a fixture, which was attached to a materials testing device. Using this device, the role of the coracoacromial ligament was evaluated by loading the shoulders in various positions and then measuring displacement before and after excision of the ligament. The mean difference in anterosuperior displacement was 3.44 mm. In all shoulders, subjective observation revealed that the humeral head often becomes wedged between the coracoid and the acromion during axial loading after excision of the coracoacromial ligament. Therefore, the coracoacromial ligament should be preserved to enhance the stability of the joint and to preserve the superior fulcrum.