A Metal/Ultrahigh-Molecular-Weight Polyethylene Cementless Surface Replacement

Abstract

Cementless metal/ultrahigh-molecular-weight polyethylene (UHMWPE) hip replacements that use less than hemispherical acetabular components and a short tapered femoral stem were developed in 1983 by the use of cobalt-chromium alloy and conventional GUR 415 polyethylene sterilized by ethylene oxide. These devices improved the fixation failures seen with cemented, fully hemispherical acetabular cups but encountered wear and osteolysis problems in the medium to long term. More wear-resistant titanium nitride ceramic bearings, developed in 1989, coupled with porous coated, cementless fixation, demonstrated midterm survivorship of 91.8% at 6 years but also developed long-term wear and osteolysis problems associated with conventional polyethylene. Recent advances in wear-resistance with the use of highly crosslinked polyethylene has prompted a renewed examination of the cementless resurfacing concept, allowing bearing exchange and retention of well-fixed resurfacing implants with these improved bearings as well as primary resurfacing hip replacement, using conventional surgical techniques. An anticipated 60%-90% reduction in wear and osteolysis, on the basis of long-term clinical and mechanical simulator data, makes this cementless application a significant alternative to cemented metal-metal resurfacing.