Congenital metatarsus varus. A suggestion for a possible mechanism and relation to other foot deformities.

The pathogenesis of metatarsus varus was investigated by a series of dissections of 14 normal feet of stillborn or infants who died during the perinatal period. The deformity could not be produced without the surgical incisions described below. A valgus position of the hindfoot was produced by maximal dorsiflexion of the foot. The deformity of the fore part of the foot could not be produced even by extreme traction on the tibialis anterior tendon even after capsulotomy of the first tarsometatarsal joint. Only extensive capsulotomies in the tarsometatarsal joints distal to the joint of Chopart made it possible to displace the bones into the position analogous to metatarsus varus. It is suggested that metatarsus varus may be a deformity which occurs on a maximally dorsiflexed foot and that the primary mechanism of the forefoot deformity is a subluxation in the fore part of the foot. Secondary contractures of the soft tissues, and adaptive bone changes offer a possible explanation for lack of spontaneous recovery as well as the difficulties encountered in treating late cases.