Clinical Overview
Reviewed by Dr. Jon Warner

The shoulder is the junction of three bones: the humerus (upper arm bone), the clavicle (collarbone), and the scapula (shoulder blade). The ball-like head of the humerus fits into the cup-like end of the scapula (known as the "glenoid" or "shoulder socket"). The head of the humerus may be forced out of the glenoid in a dislocation or can be forced partially out of the glenoid, which is known as a subluxation. Either may cause a Hill-Sachs Defect, a compression fracture in the top of the humerus, caused by the head of the humerus impacting the glenoid when the dislocation occurs. To envision this, imagine a sharp edge impacting a ping-pong ball. The defect can increase the risk of further dislocations by making it easier for the humerus to slide out of the socket.

Causes and Risk Factors
Symptoms

When the upper arm bone is forced out of socket, usually by a direct blow from behind or a fall on an outstretched hand, the humerus may hit the glenoid with great force. This may cause a Hill-Sachs Defect and its most commonly associated problem, a tear of the tissue surrounding the glenoid known as a Bankart Lesion.

Risk Factors

Frequent frontward subluxation or acute dislocation pose the greatest risk for a Hill-Sachs Defect.

Last updated: Jan-01-00