A Theoretical Model of the Effect of Bone Defects on Anterior Shoulder Instability

INTRODUCTION: The presence of either a Hill-Sachs or a bony Bankart lesion has been indicated as a possible cause of subluxation and anterior shoulder dislocation. Anterior dislocation accounts for approximately 98% of all shoulder dislocations. 2 Common treatments include soft tissue repair, bone grafting, and total shoulder replacement. It has been reported that there is a possibility of recurrent instability even after an arthroscopic or open procedure, with an incidence of 8-18%. Often, during the initial procedure, bony defects are left untreated due to a greater inclination towards soft tissue repair. Our aim was to investigate the influence of lesion size of isolated and combined Hill-Sachs and bony Bankart lesions on the shoulder's stability. Previous studies have investigated effects solely due to isolated bone lesions on the shoulder's instability. 5 This computational study investigated the effect of both bony Bankart and Hill-Sachs lesions in the glenohumeral joint on the shoulder's stability. We hypothesized that by increasing the size of isolated humeral and glenoid lesions, the stability of the joint would decrease. In addition, we expected that the presence of the glenoid and humeral head lesion together would demonstrate more instability than isolated lesions.