Natural history and treatment of instability of the hip in proximal femoral focal deficiency.

We studied 67 patients with 78 affected femurs to determine the natural history of proximal femoral focal deficiency (PFFD) with respect to hip instability and to establish guidelines for management. Using the classification systems of Aitken and Fixsen and Lloyd-Roberts as applied to a radiograph taken at age 12-15 months, we could accurately predict development of hip instability, defined as formation of a pseudoarthrosis or complete failure of hip development. The pseudoarthrosis occurred either at the cervical or subtrochanteric level of the femur. Cervical instability was difficult to treat operatively, but subtrochanteric instability fused spontaneously in 30% of cases and responded well to operative treatment when necessary. For unilateral failure of hip joint formation, various surgical procedures were used to assist prosthetic fitting, but bilateral cases were treated nonoperatively.