Total replacement of the hip joint.

Total replacement ofthe hipjoint has become a widely accepted procedure in the treatment of arthritis, and the results reported over the last few years confirm that these artificial joints can restore a high level of functional activity that is well maintained. The effects of a successful operation by any of the standard techniques are remarkably similar, the materials are well tolerated and wear is slight. The value of each procedure must therefore be measured by the proportion of patients achieving a satisfactory result, and by the number and nature of the failures. In the absence of a generally accepted method of hip assessment the comparison of results is difficult. The problem is eased, however, by the practice of expressing the outcome, not in terms of clinical improvement but in terms of normal hip function. Most patients treated by an established technique find that the joint is stable, painless, and freely mobile; such a result can be regarded as excellent. Some are left with a little residual discomfort, or minor restriction of movement, or the need for use of a stick ; they can be assessed as good, but lack the full potential of a total joint replacement. Failure may be either partial and correctable by further reconstructive surgery, or total. In 1964 we started using an uncemented metal-to-metal articulation, both parts being made of cobalt-chrome alloy. The development of the prosthesis and the early results have been reported previously in this Journal (Ring 1968) and elsewhere (Ring 1971). Four varieties of femoral component are now in current use, a longer and a shorter with a standard neck angle of 135 degrees, and a similar pair with a valgus angle of 150 degrees (Fig. 1). Each has a head 40 millimetres in diameter. The cups are all the same and interchangeable ; the screw by which the cup is fixed to the pelvis is now tapered. A Leinbach femoral component has occasionally been used in the revision of an osteotomy (Fig. 2), and a femoral component designed for fixation by cement has been introduced to deal with the loose prosthesis (Fig. 3). This paper deals with the results of the first 1,000 replacements, performed over a period of eight years. In no patient was acrylic cement used in the course of a primary operation, and even when the bone was grossly osteoporotic or the acetabulum deficient, a stable articulation was achieved. Although many of the patients have had bilateral replacement, mostly under the same anaesthetic, the results have in general been recorded as numbers of hips treated rather than numbers of patients. We have not reported separately patients whose hips had been treated primarily in other ways before coming to total replacement, because the nature of the earlier operation appears to play little part in the final result. Throughout this study we have found no evidence of any local or systemic change which might be of significance in limiting the use of a cobalt-chrome implant of this type.