Kinematics of the first metatarsophalangeal joint in intact and surgically altered cadavers.

The kinematics of the first metatarsophalangeal joint were investigated in five embalmed cadaver feet (three normal, one hallux valgus, one hallux rigidus). Sagittal displacements of the first metatarsal relative to the proximal phalanx were measured during first metatarsophalangeal joint dorsiplantarflexion; first in intact cadavers, then with an intact capsule sans extracapsular soft tissues (hallux amputated at the first metatarsal cuneiform joint), and finally with a double-stem silicone prosthesis inserted. In the intact cadaver, the base of the metatarsal is raised by FMTP dorsiflexion in a manner similar to a cam. However, this effect ceased when the extracapsular soft tissues were removed. Silicone arthroplasty did not restore cam function.