A Hill-Sachs lesion is an impaction fracture—a dent or divot in the bone—located on the humeral head, the “ball” of the shoulder joint. This injury is a direct consequence of an anterior shoulder dislocation. When the upper arm bone is forcefully pushed out of its socket, the lesion results from the impact of the bones. Its presence often indicates a higher risk of future shoulder instability and recurrent dislocations.
How a Hill-Sachs Lesion Forms
The formation of this lesion occurs during a traumatic anterior shoulder dislocation. The shoulder joint consists of the humeral head and the glenoid, the shallow socket on the shoulder blade. When the humerus dislocates forward, the softer bone of the humeral head is driven forcefully against the sharp, bony front edge of the glenoid socket.
This powerful impact causes a compression fracture, creating a distinct indentation or defect in the bone. The lesion is consistently found on the posterolateral portion of the humeral head. This characteristic divot weakens the integrity of the “ball” portion of the joint.
The presence of this defect is a significant factor in shoulder instability because it compromises the smooth, spherical shape of the humeral head. When the arm is moved into certain positions, this bony defect can catch or “engage” on the anterior glenoid rim. This engagement makes the shoulder highly susceptible to re-dislocation, reinforcing the connection between the lesion and chronic instability.
Diagnosing and Assessing Severity
The diagnostic process begins with standard plain film radiography (X-rays), which can reveal the dislocation and sometimes the lesion itself. To accurately visualize the defect, specialized X-ray views are often required, such as the Stryker notch view. This specific projection positions the arm to highlight the posterior-lateral surface of the humeral head, making the lesion more visible.
Advanced imaging is necessary to fully assess the lesion’s size, depth, and three-dimensional characteristics. A Computed Tomography (CT) scan provides detailed cross-sectional images that are considered the gold standard for measuring bone loss. Magnetic Resonance Imaging (MRI) is also frequently used, as it shows the bony defect and evaluates associated soft tissue injuries, such as tears in the labrum or rotator cuff.
The assessment of severity centers on two factors: the size of the lesion and whether it is “engaging.” An engaging lesion is one that physically contacts the glenoid rim when the arm is placed in a typical position of instability, causing the joint to subluxate or dislocate. Lesions that involve more than 20% of the humeral head’s articular surface are generally considered large and are at a greater risk of engagement. This distinction guides the subsequent treatment strategy.
Management and Treatment Options
Treatment for a Hill-Sachs lesion is determined primarily by its size, the degree of shoulder instability, and whether the lesion is engaging. For small, non-engaging defects, or in cases of a first-time dislocation, non-surgical management is typically the preferred approach. This conservative treatment focuses on a structured physical therapy program.
Physical therapy aims to strengthen the muscles surrounding the shoulder, particularly the rotator cuff and scapular stabilizers, to provide dynamic stability to the joint. The goal is to compensate for the bony defect by enhancing muscle control and improving proprioception, which is the body’s sense of joint position. This rehabilitation allows the patient to return to normal activities without recurrent instability.
Surgical intervention is required for large lesions, those that are engaging, or when non-surgical treatment has failed to prevent recurrent dislocations. The surgical strategy depends on whether the defect is addressed on the humeral head (the ball) or the glenoid (the socket). One common arthroscopic procedure to treat the humeral defect is the Remplissage procedure.
In the Remplissage procedure, the surgeon anchors the posterior capsule and a portion of the infraspinatus tendon directly into the bony divot on the humeral head. This effectively fills the defect, preventing it from catching on the glenoid rim during arm movement and stabilizing the joint. Alternatively, especially when there is significant bone loss on the glenoid side, a Latarjet procedure may be performed. This involves transferring a piece of bone from the shoulder blade to the front of the glenoid socket, which restores the socket’s size and converts the lesion from an engaging one to a non-engaging one.