Anterior shoulder instability modifies glenoid subchondral bone density

Subchondral bone mineralization is used as a morphologic marker for individual stress distribution of joints and therefore may help to distinguish variations of glenohumeral contact. Therefore, an in vivo analysis was done to evaluate glenoid stress distribution in anterior glenohumeral instability by computed tomography osteoabsorptiometry. Patients with recurrent anterior glenohumeral dislocation, seven of posttraumatic and six of atraumatic origin, and an intact rotator cuff were grouped retrospectively and compared with healthy, age-matched shoulder specimens from cadavers (n = 13). Glenoid subchondral bone mineralization, including those in all patients with anterior glenohumeral instability, indicated a more anterior and inferior stress distribution compared with stable shoulders. The position of the anterior glenoid density maximum had shifted anteriorly and inferiorly whereas the position of the posterior maximum had shifted anteriorly. Analyzing results on the basis of cause, in posttraumatic instabilities, the shift of the anterior maximum mainly was anterior and in atraumatic instabilities, it mainly was inferior. Individual glenoid stress distribution in anterior glenohumeral instability can be assessed objectively by computed tomography osteoabsorptiometry. The shift of the density maxima corresponded with anterior and inferior directions of humeral head displacement, whereas the degree of changes varied according to the cause of glenohumeral instability.