Early loosening of revision hip arthroplasty. A roentgen stereophotogrammetric analysis.

The primary migration of 15 and 22 cemented acetabular and femoral prosthetic components was recorded in 23 patients operated because of type I (minimal endosteal bone loss) and type II (thinning of bone, enlargement of femoral canal and acetabulum) mechanical loosening. Roentgen stereophotogrammetric analysis was used to measure the three-dimensional displacements of the center of the acetabulum and the femoral head. All but 1 of the acetabular and 1 of 15 revised femoral stem prostheses migrated within 2 years after the operation, whereas 5 of 7 revised femoral surface arthroplasties were stable. Femoral components with type II loosening migrated, on average, 1.5 mm (range, 0.6-3.0 mm) during the first postoperative year, compared with 0.7 mm (range, 0.3-1.1 mm) in patients with type I loosening (P less than .02). Increased bone loss of the acetabulum (type II), the quality of the bone-cement interface as judged from radiographs, and the presence of perforation of the femoral cortex did not significantly influence the rate of migration in this group. Compared with previously presented studies of cemented primary hip prostheses, cemented revisions seem not only to migrate more frequently but also at a higher rate. Poor primary fixation is probably one important cause of the high frequency of clinical failures in these patients.