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This paper describes models of artificial acetabula which are better adapted to the structural conditions of the fixation bed than the prostheses used hitherto. The most important design feature is the increased area of surface contact between the artificial acetabulum and bone by means of stepped anchoring pins, which extend radially into the spongiosa from the surface of the acetabulum. The location and length of these small anchoring pins depends on the bone architecture of the acetabulum.

A four year follow up trial of 109 cases of the Wagner type of prosthetic surface replacement has been undertaken. It has been found that this type of arthroplasty has been associated with a higher rate of loosening that the conventional total hip replacement. This loosening mainly affects the femoral component. The morphological changes which occured below the loosened femoral component did not show typical avascular necrosis due to implantation of the prosthesis. The changes seen were due to mechanical failure of the bone which resulted from previous structural weakness of the femoral head. Hence loosening of the implant occurred mainly in femoral heads which had cysts, partial necrosis or osteoporosis. Loosening of the implant was not definitely related to the position of the hip and occured in both the valgus as well as the biomechanically unfavourable varus position.

After successfully testing the new technique of IBE (intramedullary bone endoscopy) in vitro, we present the first clinical applications of the new endoscopic method. In two selected cases (cement removal in revision joint arthroplasty/complication management after intramedullary loss of a reamer) the technique of IBE was performed in vivo for the first time. Removal of cement under endoscopic guidance and salvage of the lost reamer was easily possible using the special endoscopic tools. With the new technique of IBE, endoscopic intramedullary manipulation is easily possible in vivo.