FRACTURES OF THE SESAMOID BONES OF THE THUMB

Stability of the thumb metacarpophalangeal joint is provided by the co llateral ligament proper, the accessory collateral ligament, the proxi mal and distal palmar ligaments, and the palmar plate. The adductor po llicis and flexor pollicis brevis muscles also provide soft tissue sup port and insert on the proximal phalanx of the thumb by way of the ses amoid bones. Fractures of the metacarpophalangeal joint sesamoid bones are uncommon but are often associated with sporting injuries during w hich the joint is acutely hyperextended. Routine anteroposterior and l ateral radiographs may be unremarkable, and oblique views are often ne cessary to document the fracture. We report eight cases of fracture of the thumb metacarpophalangeal joint sesamoid. Seven were isolated ses amoid fractures, and one was associated with a metacarpophalangeal joi nt dislocation. None of the fractures were evident on anteroposterior radiographs, but all were seen in the oblique projection. Six fracture s were treated with splint or cast immobilization for 2 to 3 weeks, an d two were taped. Clinical followup of the seven patients with isolate d sesamoid fracture at 6 to 8 weeks revealed pain-free normal function . One patient could not be reached for followup.