Avulsion fracture of the metacarpophalangeal joint of the finger.

Six patients with avulsion fractures of the metacarpophalangeal joints of the fingers are reported. Operation was performed in all cases. Judging from the operative findings, the radiological assessment of fragment shape is helpful in treatment. Surgery is recommended when the fragment is triangular or rectangular in shape because the fracture involves the articular surface. Conservative treatment is effective if the fragment is round because the articular surface of the joint is not involved in this type of fracture. The avulsed fragment often overlaps the metacarpal head and a collateral ligament injury is likely to be misdiagnosed. It is important to suspect this injury and assess the shape of the whole fragment for a good functional result.