The Capsular Mechanism in Recurrent Dislocation of the Shoulder

Functional lengthening of the capsule and loss of the anterior restraining effect of the capsular mechanism appear to be the primary causes of recurrent dislocation of the shoulder. Separation of the medial attachment of the capsule from the anterior glenoid margin is the most consistent cause of capsular lengthening. Congenital lengthening is probably present more often than is suspected, but interpretation is made difficult by the finding of secondary damage at the glenoid margin. The function of the normal capsule, which allows this usually lax structure to become an effective barrier against anterior projection of the humeral head in external rotation, is referred to as the capsular mechanism. Repair should aim at re-establishment of the capsular mechanism. If there is no medial capsular separation, a modification of Magnuson's procedure is adequate. If there is separation of the capsule, but capsular tissue remains at the glenoid margin, sutures into the soft tissue only need he used. If there is complete loss of soft. tissue from the anterior glenoid margin, the capsule should be anchored directly to the bone. Reattachment of the glenoidal labrum is not necessary, and the presence or absence of this structure does not alter the operative procedure or the success of the repair. Limitation of shoulder motion to prevent dislocation is usually not necessary. Bankart must be credited for focusing attention on the medial attachment of the capsule to the glenoid margin, and for gradual recognition of the correct operative procedure for the majority of cases of dislocation of the shoulder.