Metal on Metal in Resurfacing Arthroplasty: Risks or Benefits?

Abstract

At the beginning of hip endoprosthetics was the substitution of destroyed cartilage by biologigal or artificial materials. However, successful results were only achieved after the introduction of abrasion-resistant materials in combination with exactly matching differences of diameter (radial clearance) of head and socket. The cobalt-based alloy Vitalliun® which had been introduced into medical therapy by dentists in 1932 was used by Smith-Petersen [1,2] to create the world’s first hemiprosthesis (1937) available on the market. The first total hip replacement was implanted by Wiles in London, who used a metal on metal joint made of stainless steel. In the course of the development of arthroplasty and after the introduction of bone cement, the successful period of THR began. Despite the excellent long-term results achieved for metal on metal prostheses (McKee-Farrar [10], Ring) which have been implanted since the sixties, hard on soft material configurations as specified by Charnley for his Low Friction Arthroplasty have been used at an increasing extent since the mid-seventies. The reasons for this were the excellent initial results obtained from the use of such prostheses. Apart from that, abrasion and loosening of acetabular cups due to equatorial jamming had occurred in some metal on metal prostheses in which the radial clearance provided for had been inappropriate. Moreover, there had been doubts in respect of possible allergic reactions and the possibility of carcinogenic effects of the metal particles at that time already [1]. The triumphant clinical advance of THRs using metal femoral heads and plastic acetabular cups continued until the problem of polyethylene abrasion and the destruction of bone induced by particle debris occurred and required new approaches to be developed [5]. This “particle disease” stopped, either, new attempts of resurfacing arthroplasty using a metal cap which was placed on the preserved bone of the femoral head, and a thin polyethylene cup, which had been rediscovered by Wagner and other authors.