Fig. 7. Boxer's fracture. When the metacarpal head impacts a hard surface, the resulting fracture allows it to displace palmarly (1.). If the displacement is greater than can be compensated by normal joint motion, extensor tendon imbalance will result in a proximal interphalangeal joint extensor lag and eventually flexion contracture of this joint (2.). Open injuries sustained in this fashion such as the clenched fist bite wound may be difficult to assess because soft tissues shift after injury (3,4.).