[Replacement of prostheses of the hip].

In view of the widespread insertion of total hip prostheses, in recent years loosening of such prostheses requiring operative revision has become increasingly frequent. Simultaneous bone resorption defects in the acetabulum and the femur pose a particular problem. Attrition of the polyethylene obviously plays an important part in this process, its effects becoming apparent after 15-20 years. When a total prosthesis is replaced every effort should be made to reproduce the normal anatomical situation as nearly as possible. In particular, the bone defects should not be filled up with massive implants or with bone cement, but should be reconstructed with bone transplants. Mechanical protection in the form of internal fixation is necessary for the larger bone transplants; if this is not provided they may not take properly. When there are defects in the acetabulum corticospongious bone chips taken from femoral heads are used in the vast majority of cases. For larger defects in the femur, large allogeneic transplants of cortical bone taken from cadavers and applied to the defects in the form of a cuff following sterilization with gamma irradiation have given very positive results in recent years.