Acetabular reaction to the Bateman bipolar prosthesis.

The Bateman bipolar prosthesis has been used by the authors since 1974. The purpose of this study is to determine whether the implant functions as a bipolar device or as a unipolar hemiarthroplasty, which may cause damage to the acetabulum. Of 478 hips replaced from 1973 to 1983, 19 with acetabular changes were randomly selected to evaluate the response of the prosthesis. From the 11 cases with protrusio at the time of surgery, six showed thickening of the acetabular wall, while no changes were observed during ten years follow-up study in the five remaining cases; in one case, the wall gave way, and a revision was necessary. In five patients with subchondral cysts, the cysts tended to gradually disappear. Three patients showed sclerosis in the subchondral acetabular bone, which also decreased gradually. Previous facts suggest the acetabulum tolerates the implant well even with some damage at the time of surgery. Whether this depends on the amount of movement and friction occurring between the head and the insert is still undetermined.