Hill-Sachs defects are a posterolateral humeral head depression fracture, resulting from the impaction with the anterior glenoid rim, and indicative of an anterior glenohumeral dislocation. It is often associated with a Bankart lesion of the glenoid.

A Hill-Sachs defect is the terminology of preference over other terms, such as Hill-Sachs lesions, and Hill-Sachs fractures 14.  

Repeat dislocations lead to larger defects, which can result in an "engaging" Hill-Sachs defect, which engages the anterior glenoid when the shoulder is abducted and externally rotated 4 (see article: on-track and off-track shoulder lesions for further discussion) 10.

Anterior glenohumeral dislocation will lead to impaction of the posterolateral humeral head and anterior glenoid rim. Repeat dislocations can lead to further bony defects in both the humeral head and glenoid and the engaging Hill–Sachs defect is associated with decreased glenoid bone stock, glenoid rim fracture, and chronic instability 14. Bankart lesions are up to 11x more common in patients with a Hill-Sachs defect, with increasing incidence with increasing size 8. 

When a Hill-Sachs defect is identified, careful assessment of the anterior glenoid should be undertaken to assess for a Bankart lesion.

wedge shape defect in the posterolateral aspect of the humeral head

best appreciated on AP internal rotation view

smaller defects can be difficult to identify

on abduction-internal rotation views, the physiological depression at humeral head-neck junction should not be mistaken for Hill-Sachs defect and is evident 2 cm from superior humeral head margin 15

loss of the normal circular shape in the posterolateral region of the superior humeral head on axial images

MRI and CT will show smaller defects

anatomic shape can be preserved but the presence of bone marrow edema in the posterolateral humeral head indicates an acute injury

normal flattening of the posterolateral humeral head caudal to the level of coracoid should not be misinterpreted as a Hill-Sachs defect 2,4 (sometimes termed pseudo-Hill-Sachs defect)

The bony defect itself often does not require treatment, however, the associated glenohumeral instability and coexistent anterior labral injuries often do require surgical repair.

The bony defect can be treated with bone grafting or placement of soft tissue within the defect, but this is generally reserved for large, engaging defects 6,7. Capsulotendinosis and filling of the Hill-Sachs defect can be performed via open (Connolly procedure) or arthroscopic (remplissage) approaches 6,7. 

It was first described in 1940 by American radiologists Harold Arthur Hill (1901-1973) and Maurice David Sachs (1909–1987) 3,11,12. The "engaging" Hill-Sachs was described by Burkhart and De Beer in 2000 10. 

hatchet sign of ankylosing spondylitis

humeral head pseudolesion

in patients with a Hill-Sachs defect but without an anterior labral tear, particular attention should be made to assessing for potential humeral avulsion of the glenohumeral ligament (HAGL) 16