The survivorship of total hip replacements in patients operated on at the Royal National Orthopaedic Hospital has been analysed using standard actuarial methods. Between 1963 and 1972 173 metal-on-metal prostheses of various developmental designs were inserted. Between 1969 and 1972 248 prostheses of one design using a metal femoral component and plastic cup were used. The patients were surveyed retrospectively and for each the actual follow-up period was determined as well as the eventual outcome. The criterion of "survival" was that the prosthesis was still in situ and all such prostheses were regarded as "survivors", regardless of whether the patients experienced pain or loss of function. The survivorship was then determined by constructing life tables. The results indicate that for metal-on-metal prostheses the overall probability of survival was only 53 per cent after 11 years and the average annual probability of removal, irrespective of cause, was 5.5 per cent. The results were better for metal-on-plastic prostheses with figures of 88 per cent after eight years and 1.5 per cent respectively. For both prostheses the predominant reason for failure was loosening and the annual rate of removal for loosening increased as the follow-up time increased, suggesting that loosening was a wearing out process. The advantages of the survivorship method of analysis as compared with conventional methods are discussed.

No abstract

No abstract

A series of 81 patients has been reviewed to determine the value of endoprosthetic replacement of the proximal femur and hip in the treatment of bone tumours. Standard statistical methods were used to evaluate the survival of the replacements and the patients. Taking removal of the prosthesis, irrespective of the cause, as the criterion for failure the survival of the replacements was found to be 63 per cent after 10 years. If deaths are regarded as failures, then the survival value falls to 48 per cent. The survival of patients with chondrosarcoma and osteoclastoma treated by endoprosthetic replacement compares favourably with survival after amputation or excision of the tumour.

No abstract

No abstract

At the Royal National Orthopaedic Hospital major replacement of long bones began in 1949, and the first titanium-containing endoprosthesis was inserted in 1964. By now over 250 titanium-containing endoprostheses of various kinds have been inserted. Most of these components were made on a modular basis and included sections of cast cobalt-chromium-molybdenum alloy. In 1972 titanium alloy 318 (Ti-318)(Ti-6Al-4V) was introduced, and this alloy largely replaced the previously used commercially pure titanium. This paper presents our experiences with these endoprostheses, with titanium total hip replacements, and with other titanium devices. Using standard statistical methods, survival curves for the nonremoval of the component were obtained. These curves demonstrated that the performance of upper femoral, lower femoral, and upper tibial endoprostheses was slightly worse than that of standard total hip replacements. This worse performance was a result of five intramedullary stem fractures, but we now think that this problem has been overcome by the introduction of Ti-318. These and other fractures emphasize the importance of good design, good surface finish, and optimum stem or section size. There was no evidence that the combination within a single implant of cobalt-chromium-molybdenum and titanium, commercially pure or alloy, caused corrosion or clinically significant problems. Although blackening of adjacent tissue has been observed, there was no evidence that this was associated with an undesirable tissue response.

The paper compares four alloys in orthopaedic implant use on the basis of their performance in laboratory tests. The alloys compared were cast Co–Cr–Mo, powder metallurgy (PM) Co–Cr–Mo, Ti 318 and Ti 550. Tensile, corrosion fatigue, and corrosion tests were carried out and the effect of heat treatment and of surface treatment was investigated. The corrosion fatigue tests ranked the alloys in the following order of merit (1) Co–Cr–Mo (PM), (2) Ti 550, (3) Ti 318, and (4) cast Co–Cr–Mo. The corrosion tests demonstrated for cast Co–Cr–Mo the effect of passivation, steam sterilization, and texturing, and for Ti 318 the effect of oxidizing, anodizing, and acid etch/shot peening. It was concluded that for joint replacement applications requiring the highest corrosion fatigue strength regardless of cost and neglecting the possible importance of elastic modulus, Co–Cr–Mo (PM) was best. For applications requiring ease of manufacture and allowing a lower corrosion fatigue strength, cast Co–Cr–Mo was the material of choice. For most other applications and in particular where high corrosion fatigue strength at a reasonable cost was required, the Ti alloys offered worthwhile advantages.