Anterior Shoulder Instability Is Associated With an Underlying Deficiency of the Bony Glenoid Concavity.

Purpose: To determine whether anterior shoulder instability is associated with an inherent deficiency of the bony glenoid concavity, which results in a reduced bony shoulder stability ratio (BSSR).

Methods: In this case-control study, we searched the institutional database for patients treated for unilateral recurrent anterior shoulder instability. We included 30 consecutive patients with atraumatic instability, 30 consecutive patients with traumatic instability, and 36 matched healthy controls, for a total of 96 shoulders.