These studies are intended as a critical contribution to the question, wether the McKee-Farrar (MF) prosthesis, on account of its stronger friction and the consequences of this, as compared to other models, still has its justification or wether these "secundary" manifestations indicate that this prosthesis should be abandoned. Studies on primary and secundary alteration of the surface were carried out on exchanged MF prosthesis with the aid of the grid electron microscope. The signs of wear are clearly visible and can be differenciated from production artefacts. The movement and deposit of abraded particles into the new joint capsule was studied qualitatively and quantitatively with the aid of radioisotopes. All samples showed an increased accumulation of chrome in the tissues as compared to cobalt. There is no indication of significant damage. On the basis of the results of these studies and on account of the favourable personal experience from a surgical and clinical point of view -- particulary with reference to minimal preparation of the acetabulum and ready replacement, the MF prosthesis will continue to hold its place as the standard model for total prosthetic hip joint replacement.

Recently aseptic loosining of the acetabular part in patients with allo-arthroplasty has also become a numerically increasing problem. Different opinions exist regarding the etiology, they range from mechanical to tissue factors. Favourable personal experience with careful handling of the bony acetabulum during surgery appeares to confirm that the size and type of treatment of the acetabular wound during implantation of the acetabular prosthesis are significant factors for the durability of the allo-arthroplasty. A formula which was compiled indicates and clearly shows how the increase in area of the acetabular wound depends on the increase of the acetabular radius. In addition, the laws of cellular reaction from general pathology should be the reason to limit damage to living tissue to the absolutly necessary extent.

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