[Study of loosening and wear of total hip prosthesis. Apropos of a series followed-up over 10 years].

After reviewing 30 cases of patients having had a total hip arthroplasty by the Charnley's technique between 1970 and 1978, the authors study the radiographic parameters of the cup and of the femoral stem, using geometric buildings described by Sutherland. On the acetabulum, the inclinaition angle, the medialisation and the wear of the cup were calculated. The varisation of the stem and its migration were looked for on the femur. The presence of a radiolucent line, prosthesis--bone or cement--bone and the importance of peri-articular calcifications, was also noted. The verticalisation of the cup and its anteversion were a pejorative factor. The medialisation was disquieting only if it was associated with a verticalisation. The wear more than 2 mm was noted only in 5 cases; the radiolucent line was pejorative only if it was type cement--bone; the type cement--cup, rare, was of less bad prognostic. On the femur, the most failing was the varus of the stem which determined a loosening most often when it was present. The disquieting radiolucent line was always type cement--bone and was always associated with a bicortical reaction showing a mobility of the stem. In a last part, the authors studied the wear of expanted cups in polyethylene which was different of the fluage. A distinction between the theoretical wear and the clinical wear was made. Photographs in scanning electron microscopy which permit to describe the different types of wear are presented.