A study has been made of 129 patients with congenital dislocation of the hip, with the object of determining the causes of failure in the treatment of this condition.

The cases were divided into the following three groups:

1. Prenatal dislocations, where the dislocation is present at birth;

2. Postnatal dislocations, where the patient presents a predislocation at birth, which slowly progresses during the first year of life until it becomes a well-established dislocation when the patient begins to walk. The bilabiation of the acetabular roof shown on the roentgenogram is characteristic of most of these cases.

3. Doubtful cases, where both the primary and secondary acetabula are well developed, but where the roentgenogram shows them to be separated by a bony ridge. In these cases, it was impossible to determine how and when the dislocation took place.

Treatment in the prenatal cases generally resulted in failure. Putti's abduction splint is indicated only during the predislocation stage of the postnatal dislocations.

The anteversion of the femoral neck plays an important rôle in the maldevelopment of the hip after immobilization.

Two types of lesions indicative of the changes that take place in the femoral head after reduction are cystic atrophy and fragmentation. A flat or an irregular head may result from such lesions. Osteosclerosis and cystic atrophy may be observed in the acetabular roof.

An evaluation is made of the type of dislocation, and of the results obtained with different treatments.

The causes of failure in the treatment were studied at the time of reduction, during the period of immobilization, and after immobilization. Except for the prenatal dislocations, which have a poor prognosis under any treatment, the main causes of failure were found in: (1) the epiphysitis of the femoral head, (2) the tendency toward subluxation, which occurs at the beginning of the walking exercises, and (3) the osteosclerosis of the acetabular roof.

To improve the treatment, the author proposes to limit the period of immobilization in a plaster cast to from five to six months, this to be followed by a prolonged period of functional after-treatment, controlled with an abduction bar. The abduction bar was devised with the object of avoiding adduction and outward rotation of the hips, but allowing them free motion in other directions.