A study of acetabular development in 148 patients with 185 congenitally
dislocated hips treated by closed reduction from 1940 to 1968 showed that
eight years after reduction the acetabular index was normal (less than 20
degrees) in 49.2 per cent, satisfactory (from 20 to 24 degrees) in 34 per
cent, and poor (more than 24 degrees) in 16.7 per cent. Early treatment led
to the best acetabular development. Significant and continuing improvement
of the acetabular index was observed between two and eight years after
reduction when the femoral head remained concentrically reduced. Failure to
maintain proper reduction and necrosis of the femoral head led to poor
results.