Treatment of secondary osteoarthritis and rheumatoid arthritis by Bateman hip prosthesis.

The Bateman hip prosthesis was applied in reconstruction of secondary osteoarthritis and rheumatoid arthritis. Forty-five joints that could be followed up for 45-18 months (mean 26 months) were clinically and roentgenographically re-examined. Forty joints (90.0%) were painless. The clinical score improved from the preoperative mean of 44.8 to the postoperative mean of 87. In 34 patients with secondary osteoarthritis, postoperative protrusion of the outer head into the acetabulum reconstructed by excavation of the previous shallow, steep architecture was only 0.8 mm (mean). Postoperative protrusion of the outer head into the acetabulum reconstructed by bone grafting was only 2.0 mm (mean) in 11 patients with rheumatoid arthritis. Roentgenograms revealed the appearance of sclerosis supermedially in the excavated acetabulum 4-6 months after the operation. This sclerotic change expanded in the entire area of contact with the outer head in 36 of 45 joints within about 1 year. Once the sclerosis had spread completely, the outer head stopped protruding into the acetabulum. A computerized simulation experiment with a rigid spring model demonstrated that central displacement of the outer head can be avoided if the continuity between the sclerosis in the articular surface of the reconstructed acetabulum and the lateral wall is restored for transmission and dispersion of the resultant head force toward the lateral wall as in normal hip joints; this verified the clinical findings.