Second generation of metal-on-metal cemented total hip replacements: 12 years of clinical and biological follow-up

Abstract

The second generation of metal-on-metal prostheses appeared at the end of the 1980's as a serious alternative to metal on polyethylene bearing couples. Short-term clinical results were promising; however certain questions remain concerning clinical, radiological and biological aspects. Release of chromium and cobalt from the bearing couple is one of these aspects. The aim of this study is to analyse the results of a series of 97 cemented total hip prostheses comprising a titanium femoral stem and the Metasul ® metal-metal bearing couple. Mean follow-up was nine years (7-12 years). Complications were marked by 12 revisions, out of which two were for recurrent early dislocations, eight for clinical and radiological failure, and two for worrying radiological alterations. During these revisions, we observed a serious infiltration of metal debris four times, leading to an alternative strategy using an alumina-alumina bearing couple. Three more revisions are planned for rapidly evolving radiological alterations. Thirty implants showed radiological signs of preoccupying deterioration on the acetabular side. Eight segmentary femoral osteolysis have been observed. Twelve patients suffer from recurrent subluxation. Concerning the global evolution of metal serum levels, cobalt remains stable after five years. The values are three to four times above those of a non-exposed subject, but largely below toxic ratios. The evolution of serum chromium levels is similar to cobalt. Implantation of two prostheses in one same patient leads to significant increase in serum metal ratios. This series raises questions concerning the reliability of the metal-onmetal bearing couple. Osteolysis is an unsolved problem. Today, cemented fixation is debatable although this series doesn't allow this parameter to be held directly responsible. Nothing points to any shortcomings concerning the taper fixation or the metallurgy of the femoral stem. The study of the serum metal levels seems a good indicator of the impingement situations and the functioning of the bearing couple.

Metal-on-metal: history, state of the art (2010)

“…If the absence of industrial coherence could perhaps explain certain failures [29], the limitations of cementing these types of cups became rapidly apparent [31]. However, the combination of this same type of insert in a metal reinforcement [16] yielded good results.…”