Hallux valgus--an acquired deformity of the foot in cerebral palsy.

In this series, acquired hallux valgus deformity occurred in those cerebral palsied children who, when initially seen as prewalkers, had neutral foot alignment and then developed a stance and gait pattern of flexion-adduction at the hips, flexion at the knees, and equinus of the feet, with external torsional effect in the leg below the knee forcing the foot into relative equinovalgus. This resulted in an abducted forefoot manifested primarily as a hallux valgus. The one variation to this premise was the equinovarus heel and adducted forefoot. Here, the resultant thrust was on the lateral border of the foot, and hallux valgus did not occur. In all instances where the response to surgery is incomplete, the foot deformity will develop. Finally, it is noted that a posterior tibial lengthening added to the surgical procedures done for the equinovarus foot has the potential ability in the cerebral palsied child to convert an equinovarus, which does not produce an acquired hallux valgus, into equinovalgus, which does produce this deformity.