Abnormalities of the hook of the hamate in patients with carpal tunnel syndrome.

The hook of the hamate is an important landmark in endoscopic carpal tunnel release. We studied the incidence of abnormalities of the hook of the hamate in patients with carpal tunnel syndrome. One hundred thirty-one consecutive patients presenting with carpal tunnel syndrome underwent carpal tunnel radiography. Abnormalities of the hook of the hamate were present in 6 of 131 patients (4.6%). The hook of the hamate was aplastic in 3 of 131 patients (2.3%). A bipartite hook of the hamate was present in 1 patient (0.8%). A nonunion of an old fracture of the hook of the hamate was found in two patients (1.6%). The previously reported incidence of an aplastic hook of the hamate in the general population is 1 of 1,452 (0.06%). The odds ratio revealed a 34-fold increase in the risk of hamate abnormalities in the carpal tunnel population (p < 0.001). Hook of the hamate abnormalities may be more common than previously reported.