Dislocation of the first metatarsophalangeal joint with fracture of fibular sesamoid. A case report.

Dorsal dislocations of the first metatarsophalangeal joint are classified by Jahss into two types. In Type 1, the hallux with the intact intersesamoid ligament dislocates dorsally over the metatarsal head. Such cases in the literature have been irreducible by closed manipulation. In Type 2 the hallux is dislocated dorsally with rupture of the intersesamoid ligament, resulting in wide separation of the sesamoids (Type 2A) or a transverse fracture of one or both sesamoids (Type 2B). The importance in classifying these injuries allows one to predict whether closed reduction will be successful as in Type 2. The patient reported had a fracture of the fibular sesamoid in addition to dislocation of the hallux. The clinical findings were consistent with Type 1 injury, including an intact intersesamoid ligament, but the radiographs showed, in addition to the dislocation, that there was a fracture of the fibular sesamoid. Reduction was achieved surgically through a dorsal approach. Although such injuries have been unreported previously, Type 1 injuries may be associated with a fracture of the fibular sesamoid but without rupture of intersesamoid ligament, so the injury reported is classified as Type 1A.