Motorcyclist's thumb: carpometacarpal injuries of the thumb sustained in motorcycle crashes.

UNLABELLED: The purpose of this study was to investigate motorcycle crash thumb injury patterns. We hypothesized that ulnar collateral ligament injuries at the thumb metacarpophalangeal joint would be most common and there would be a side predilection due to the clutch and brake positions. Motorcyclist admissions following injury between 2002 and 2013 were reviewed, and phalangeal and metacarpal injuries treated acutely identified. Demographics, injury, and treatment characteristics were recorded. Association between laterality and injury type was assessed. Of 128 patients, 59 underwent acute treatment for thumb injuries. Eleven patients sustained thumb ulnar collateral ligament injuries; 27 sustained thumb carpometacarpal injuries. Most carpometacarpal injuries were fracture-dislocations (19/27). Thumb carpometacarpal injuries had no overall side predilection; ulnar collateral ligament injuries occurred more on the right. Carpometacarpal fractures and dislocations are the most frequent motorcycle crash thumb injury, probably due to the mechanics of gripping handlebars and the high-energy force directed into the palm and against the metacarpal base. LEVEL OF EVIDENCE: Level IV.