Migration of the acetabular socket after total hip replacement determined by roentgen stereophotogrammetry

In order to evaluate the feasibility of a roentgen stereophotogrammetric method for the analysis of the migration pattern of joint prostheses, tantalum balls were implanted into the acetabular socket and the pelvic bone during total hip replacement in four patients with rheumatoid arthritis. During the postoperative period, the migration of the acetabular socket was determined. The observation period varied from 5-24 months. No clinical or radiographic signs of mechanical loosening or infection were noted. All the investigated patients showed a gradual migration of the acetabular socket. The cranial migration measured up to 1.8 mm in 2 years. The migration along the transverse and sagittal axes was less but not constantly directed. The rotatory movements about the three axes varied and measured up to 5.5 degrees in 2 years. The translation and rotation were greatest during the first few months. The results indicate a gradual migration of the acetabular socket in hip arthroplasty in the osteopenic skeleton in rheumatoid arthritis.

roentgen stereophotogrammetry may prove to be a valuable means of analysing the migration of implanted prostheses and detecting prosthetic loosening, thereby increasing the possibility of early and correct diagnosis and therapy.