Location of the Glenoid Defect in Shoulders With Recurrent Posterior Glenohumeral Instability

Abstract

Posterior bone defects in the setting of posterior shoulder instability most commonly occur in the posteroinferior quadrant of the glenoid and extend on average from 6:44 to 9:28 (81.5° total degrees of arc) on a clockface model. Posterior bone loss occurs at a mean of 30° off the long axis of the glenoid in a posteroinferior direction, which is historically different from anterior bone loss, which occurs parallel to the long axis of the glenoid. This study serves to highlight the location and orientation of bone loss that one can expect in a patient with recurrent posterior shoulder instability, although additional work is needed to assess why this develops.