Primary recognition and treatment of congenital dislocation of the hip.

The pathology associated with congenital dislocation of the hip has been reviewed. The pathophysiology as it affects the development of the hip under treatment makes a strong case for the avoidance of the "frog leg" position with fixed flexion and abduction of the hips in the plaster cast. It is apparent that tightness of the iliopsoas muscle and the underlying capsule makes that flexed abduction position necessary to hold the hip in position. The "frog leg" position is seriously implicated in the development of aseptic necrosis, not only of the dislocated hip but of the normal hip as well. The results seen in patients with surgical division of the iliopsoas tendon and capsular contracture, followed by leg immobilization in a functional position of extension at the hip accompanied by slight abduction and internal rotation, indicate the virtual elimination of the necessity for secondary reconstruction procedures on the hip at a later date. This appears to be the more conservative approach to treatment in children under age two. A period of one to three months in a splint that flexes and abducts the leg but permits changing positons may be tried before the obstruction is relieved. For children with lax capsule and iliopsoas, reduction may be possible by this route. For most the hip will be pressed in slightly improving the x-ray picture--but with the obstruction still before the femoral head. The seating of the femoral head must be exact. If it is not, imperfection in the development of the hip arises and may lead to later malfunction. Obstructions to perfect seating of the femoral head in the acetabulum must be overcome.