Department of Orthopaedics, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.

An anatomic study was designed to test the hypothesis that the articular surface of the glenoid fossa and labrum produces a composite socket of significant depth. Measurements were obtained from 25 anatomic specimen shoulders. The glenoid articular surface and labrum combine to create a socket that is approximately 9 mm deep in the superoinferior (SI) direction and 5 mm deep in the anteroposterior (AP) direction. The circular, pliable, fibrous labrum contributes approximately 50% of the total depth of the socket. Detachment of the labrum anteriorly, as in a Bankart lesion, may reduce the depth of the socket in the AP direction from approximately 5.0 to 2.4 mm. These anatomic observations provide some evidence that the socket may be an important factor in shoulder stability. Further in vivo kinematic studies of shoulders will be needed to better define the stabilizing role of the glenoid-labral socket.