Variations in Hook of Hamate Morphology: A Cadaveric Analysis

Purpose The hook of the hamate is an anatomical structure that separates the ulnar border of the carpal tunnel from Guyon’s canal and serves as a landmark for surgeons. The hook of the hamate is also subject to fracture from injury. We hypothesize that there are variations in the hook of the hamate in the general population. Methods One thousand pairs of hamates (2,000 hamates) from the Hamann-Todd Collection at the Cleveland Natural History Museum were analyzed. The height of the hook of the hamate and the total height of the hamate bone were measured using digital calipers. The hook height ratio was defined as the hook height divided by the total height of the hamate. Statistical analysis was performed using unpaired Student’s t test to determine differences in sex and race. Results The mean hook height was 9.8 ± 1.4 mm (range, 2.5–15.9 mm), whereas the mean hook height ratio was 0.42 ± 0.04 (range, 0.15–0.56). There was a 3.1% (62/2,000) incidence of abnormally small hooks, which we classified as hypoplastic and aplastic. Of the hypoplastic hooks, 55% (24/44) were bilateral, whereas 44% (8/18) of the aplastic hooks were bilateral. The incidence of variation in size in the hook of the hamate was highest in white females (9.3%) and lowest in black males (1.4%). Conclusions Abnormalities in hook of hamate anatomy are common in the general population, especially in white females. Clinical relevance Knowledge of anatomic variation in the hook of the hamate may provide additional insight into surgeons’ palpation of bony anatomy, interpretation of imaging studies, and use of the hook as a landmark during surgery.