The Prevalence of Unanticipated Hamate Hook Abnormalities in Computed Tomography Scans: A Retrospective Study

 Background:It is possible that some hamate hook fractures are not diagnosed or treated, thereby affecting the study of their natural history. Study of the prevalence of incidental hamate hook fractures, nonunions, and other abnormalities on computed tomography (CT) ordered for another reason could document a subset of undiagnosed and untreated hamate hook fractures which might change our understanding about the natural history.Methods: Reports of 2489 hand, wrist, and forearm CT scans for hamate hook abnormalities were searched. We excluded 19 patients with anticipated hamate fractures and 1 patient that had a hamate hook excision. Twenty-eight patients had an unanticipated hamate hook abnormality.Results: There was a significant difference in the prevalence of incidental hamate hook abnormalities by sex but not by age. Among the 28 unexpected hamate hook abnormalities, there were 16 fractures of the base (12 acute, 1 nonunion, and 3 of uncertain age), 5 acute oblique fractures, and 7 tip abnormalities/ossicles. The patient with an incidental nonunion had a CT scan for wrist pain and was diagnosed with gout.All fractures involved a direct blow to the hand (distal radius or scaphoid fracture, or crush injury). The 7 patients with a hamate tip abnormality had a CT scan for a distal radius or metacarpal fracture, crush injury or wrist pain. Five acute fractures were treated operatively with excision and the other 23 fractures were treated nonoperatively.Conclusion: Hamate fractures can be diagnosed incidental to other hand and wrist problems on CT.