Aseptic loosening of cement-anchored total hip replacements.

The special conditions contributing to the loosening of 61 hip prostheses were studied and compared with 325 clinical and roentgenologically intact total hip replacements. The loosening rate rose sharply after the 6th postoperative year. One third of the artificial joints examined showed signs of loosening after the 9th year. The average loosening rate was 15.8% after 5.8 years. The condition of the bony bed apparently plays an important role, both qualitatively and quantitatively, in the success of the implant. The operative procedure is of equal importance. Deep fraising of the acetabulum, removal of insufficient amounts of cancellous bone from the proximal femur and inadequate embedding of the prosthesis stem, implantation of the stem in varus, and the use of long-neck femoral head prostheses are all factors which increase the risk of loosening. Ultimately, it is the sum of these loosening factors including the biological reaction of the tissue to the biomechanical and biochemically active foreign body which, depending on the period of influence, leads to prosthesis loosening. It is imperative that the patient's lifestyle be adjusted accordingly since external weight-bearing stress also affects durability of the prosthesis.