Contribution of passive bulk tissues and deltoid to static inferior glenohumeral stability.

The relative stabilizing effect of the passive bulk tissues and deltoid to inferior humeral displacement was studied. The humeral head center relative to the glenoid center was determined by a magnetic tracking device in 10 shoulder specimens for the bulk tissue study and in 13 for the deltoid study. Twelve static recordings were obtained per specimen: (1) with and without a 1.5 kg load, (2) with the humerus adducted hanging freely and abducted 90° in neutral rotation, and (3) in three stages of dissection: with all tissues intact, after removal of the tissues superficial to the deltoid, and after removal of the deltoid. In both humeral adduction and abduction, the passive bulk tissues and deltoid did not provide significant stability to the shoulder joint.