Factors responsible for the development of avascular necrosis secondary to the treatment of congenital dislocation of the hip.

We present 104 cases of unilateral congenital dislocation of the hip treated with the same regime between 1977 and 1988. The patients had an average age of 12 months (range 4-24). The average age at follow-up was 6 years (range 3-13). The incidence of avascular necrosis was 37%. Avascular necrosis presented most frequently in babies of 7 months at the start of treatment, in Tonnis type IV when an adductor tenotomy was not performed, and after open reductions. The most influential factor was the absence of the femoral head descent at the end of the period of traction. The "effective" prereduction traction and the performance of an adductor tenotomy when necessary were the principle factors in avoiding avascular necrosis.