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Alternative Bearing Surfaces for Replacement Hip Joints

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My view:

All artificial hip joints create wear particles:

  • Metal-on-plastic joints were developed to overcome issues seen with metal-on-metal pre-1960’s.
  • Metal-on-metal was revived in the last 10 – 20 years because of the osteolysis problems caused by the plastic wear particles and because the harder surfaces, in theory, would last longer in younger patients who are going to have the hip implants for longer.

In my view there has been a big disconnect between surgeons, materials scientists, and medical implant manufacturers who have almost blindly figured that “it is metal, it is hard, it must work”, without approaching it in a unified way – the academic pride of the surgeons and the blithe greed of the medical device management have, in my view, plainly ignored the scientific facts:

  • all metals will corrode in a warm salty solution (our tissue) – hello …

Summary from the Article

The articulating joints of hip prostheses generate wear debris, and accumulation of wear particles in the local tissues can result in osteolysis, which may ultimately require replacement of the prosthesis. The purpose of new hip bearing materials is to extend implant life by substantially decreasing the amount of wear debris generated thus greatly reducing, or even eliminating, the incidence of osteolysis.

In past decades, surgeons focused on achieving excellent implant fixation during total Hip Arthroplasty (THA) because good initial fixation generally was considered to be a reliable predictor of the future performance of a device. In the 1990’s, it became clear that polyethylene wear debris generated with time by the articulating bearing surface of a hip implant was associated with the occurrence of osteolysis, often leading to reoperation and possibly shortening the useful life of an implant [12,14,17,20]. As average life expectancy continues to increase and younger and more active patients have THAs, limiting the amount of wear debris could help extend the average life expectancy of an implant [4,5,19]. Bearing combinations include polymeric, ceramic, metallic, and carbon fiber PEEK materials. These materials are categorized as hard or soft, with polymers classified as soft and ceramic and metallic materials classified as hard. Advances in the existing class of hard/soft bearings have been made also. Each bearing combination has strengths and potential weaknesses; however, all of these new bearing combinations exhibit wear that is reduced compared to the wear of earlier hip bearings.


M. Manley and K. Sutton (Download paper here)

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