What causes the Hatchet sign in the humeral head on radiographs?
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The Hatchet sign is caused by a circumscribed erosion or depression of the superolateral aspect of the humeral head. It is classically described on radiographs in ankylosing spondylitis, and has also been reported in rheumatoid arthritis and other inflammatory arthropathies. Ongoing enthesitis/synovitis and mechanical joint stress lead to focal bone resorption and erosion, resulting in the characteristic hatchet-shaped deformity of the articular surface.
Why is it called so?
It is called the “Hatchet sign” because the localized erosion creates a distinctive hatchet-shaped contour on the superolateral surface of the humeral head. This sharp angular defect resembles the blade of a hatchet or small axe, distinguishing it from other articular abnormalities.
Pathophysiology
Chronic enthesitis and synovitis at the rotator cuff insertion, combined with repetitive mechanical stress, cause subchondral bone and articular cartilage destruction. As bone resorption progresses, a sharply demarcated defect develops at the superolateral aspect of the humeral head, altering the normally smooth curvature into the characteristic hatchet-like outline. This reflects underlying inflammatory joint disease compromising both anatomy and function.
Alternative names: None
Other associated named signs: Distinguished from the Hill-Sachs defect, a posterolateral humeral head depression from anterior shoulder dislocation, which has a different location and mechanism.
References
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