HAND INJURIES ARE extremely common in pediatric patients, with 20% to 30% of fractures involving the physis. Displaced distal phalangeal fractures that involve the physis with an associated nailbed laceration are termed Seymour fractures. Because a laceration is often associated with the fracture, technically these are open fractures.

The original description by Seymour included metaphyseal fractures 1 to 2 mm distal to the epiphyseal plate, Salter-Harris I fractures, and SalterHarris II fractures.5 Because the extensor tendon inserts into the epiphysis of the distal phalanx and the flexor digitorum profundus tendon inserts into the metaphysis, Seymour fractures typically result in a flexed posture of the distal phalanx, resembling a mallet finger. However, no tendon disruption is present in these injuries, rather the disruption causing the imbalance between the flexor and the extensor tendons occurs at the level of the fracture, typically about the physis. Isolated extensor tendon ruptures are rare in children because the physeal region is weaker than the insertion of the tendon. Additional reasons for the fracture occurring in this location are the inherent weakness about the physis, the angulation of the diaphysis compared with the epiphysis, and the direction of force at the time of injury.