A follow-up study of thirty-six patients with forty dislocated hips, treated by Colonna's capsular arthroplasty at The Hospital for Special Surgery between 1936 and 1964, led to the following conclusions:

1. Regardless of the cause of the dislocation, a majority of well established dislocations of the hip in which the two joint surfaces are markedly disproportionate can be successfully reduced and stable functional joints can be produced by Colonna arthroplasty, provided that the femoral head is spherical and can be pulled down opposite the true acetabulum.

2. Traction, continued for sufficient time to pull the femoral head down to the level of the true acetabulum, is an essential preliminary step. In some instances when the arthroplasty is performed, the femoral head can be mobilized sufficiently by soft-tissue release without preliminary traction. However, preliminary traction should always be employed unless contraindicated. Previous surgical treatment or infection with subsequent scarring may make traction ineffective.

3. Other technical factors (the construction of an adequately deep acetabulum at the proper level or close to it, derotational femoral osteotomy to correct excessive anteversion when present, postoperative immobilization in a plaster spica for not longer than three to six weeks, and early resumption of movement while delaying weight-bearing) are also important in gaining good results.

4. After the initial recovery period of from two to three years, the functional qualities of adequately reconstructed hips remain stable, at least for the years spanned by this study.

5. The indications for capsular arthroplasty as outlined by Colonna can be extended to include bilateral congenital dislocation of the hip; paralytic dislocation secondary to lower motor neuron or root lesions; and certain healed septic dislocations. The age restriction (three to eight years of age) proposed by Colonna can be expanded, partticularly for paralytic dislocation.

6. The subluxated hip fixed in a false acetabulum is the most difficult type to treat by this method and probably constitutes a contraindication to its use.