Fractures of the sesamoid bones of the thumb.

Sesamoid fractures of the metacarpophalangeal joint of the thumb may be classified into two types: (1) with palmar plate intact, and (2) with palmar plate ruptured. In type 1, the patient maintains a normal flexion posture of the metacarpophalangeal joint as well as the ability to flex the metacarpophalangeal joint and interphalangeal joint. In type 2, the metacarpophalangeal joint assumes a hyperextension posture and the patient is unable to flex the metacarpophalangeal joint. Three cases are described to illustrate the two types of the injury. An open fracture of a thumb sesamoid associated with laceration of the palmar plate in a child was treated by reapproximating the palmar plate and the fracture fragments with sutures. Two additional closed fractures of the thumb sesamoid were treated by splinting the metacarpophalangeal joint in comfortable flexion for 2 to 3 weeks. Normal hand function was restored in all the three patients.