Understanding the Injury Mechanism in Hamate Hook Fractures by Investigating Fracture Morphologies: A Case Series Study.

Background: Many studies have described hamate hook fractures resulting from direct force from sporting tools. However, several authors have reported fractures that did not occur during swing-related activities. This study aimed to understand the injury mechanism of fractures by investigating their morphologies.

Methods: We selected patients with hamate hook fractures and collected data on computed tomography scans, injury causes, and how athletes handled sporting tools.

Results: We investigated 50 patients, and the study cohort included 32 patients who sustained injuries during sports: 24 during baseball (group A) and 8 during other sports (group B). Sixteen patients sustained injuries from falls (group C), and 2 had their hands crushed while using an industrial press machine (group D). In group A, most patients had a fracture line starting from the middle section of the radial side, accompanied by osteosclerotic changes in their lower hand. In group B, most patients had fracture morphologies similar to those of most patients in group A. The main morphology of fractures in group C was a transverse fracture at the base. Two patients in group D had minimal fragments at the tip of the hooks.

Conclusions: Our results question the theory that most hamate hook fractures in athletes are caused by direct force exerted on the palm because the fracture morphology was different from that of patients injured by acute trauma from direct force. Instead, these fractures likely stem from an indirect mechanism involving repetitive force generated by the tendons and muscles acting on the hook.