Multidirectional instability of the shoulder: pathophysiology, diagnosis, and management.

Multidirectional instability of the shoulder is a complex entity. Relatively few series of patients with this condition have been reported. Affected patients have global (anterior, inferior, and posterior) excessive laxity of the glenohumeral joint capsule and a rotator interval capsule defect. The onset of symptoms is frequently related to atraumatic events. The chief complaint is more often related to pain than to instability per se. Symptoms are mostly experienced within the midrange of glenohumeral motion. Because the contralateral shoulder is often equally lax and asymptomatic, it appears that factors in addition to excessive capsular laxity play a pathophysiologic role. These factors may include subtle losses of strength and/or neuromotor coordination of the rotator cuff and scapular stabilizing muscles, defective proprioceptive responses, and the absence of a limited joint volume. Most patients can be successfully treated nonoperatively with a specific exercise program. If a 6-month trial of nonoperative management fails, the patient is a candidate for surgical reconstruction. The most time-honored procedure is an open inferior capsular shift, which corrects excessive global laxity of the capsule and the rotator interval defect.