Fractures of the sesamoid bone of the thumb.

Fracture of thumb sesamoids is a rare injury. We are reporting four cases. In two cases, the fracture involved the ulnar sesamoid and in two others, the radial sesamoid. The right thumb was affected in two patients and the left thumb in the other two. In one patient, arthrography of the metacarpophalangeal joint of the thumb demonstrated contrast leakage from the volar aspect of the joint and confirmed volar plate rupture. All patients were treated conservatively with immobilization. Normal hand function was restored in all four patients. Sesamoid fractures may accompany severe injuries of the fibrous plate. Radiologists and orthopaedists should be aware of the possibility of this fracture in injuries of the thumb. Early recognition of the fracture leads to appropriate treatment and avoids possible instability of the metacarpophalangeal joint.