Traumatic dislocations of the first metatarsophalangeal joint.

The mechanics, anatomy, and pathomechanics of traumatic dorsal dislocation of the first metatarsophalangeal joint are discussed. There are two basic types of dislocations. In Type I, dislocation of the hallux with the sesamoids occurs without disrupting the sesamoid mass. Such cases are usually irreducible on closed reduction, the metatarsal head being incarcerated by the conjoined tendons with their intact sesamoids. In Type II, there is either associated disruption of the intersesamoid ligament (Type IIA) or a transverse fracture of one of the sesamoids (Type IIB). In Type II, the sesamoid disruption usually permits closed reduction.