Metal Levels in Cemented Total Hip Arthroplasty

Abstract

In a prospective study, synovial fluid metal levels from stainless steel, cobalt–chromium, and titanium–alloy cemented total hip implants were measured. There were 37 well–fixed and 44 loose hip arthroplasties. Tissue–metal levels were quantitated in the cases revised for loosening. Retrieval analysis for implant wear was performed. Synovial fluid analysis showed a fivefold increase in metal levels of loose compared with well–fixed stainless steel implants. There was a sevenfold increase in metal levels of loose compared with well–fixed cobalt–chromium implants. There was a 21–fold increase in metal levels of loose compared with wellfixed titanium–alloy (Ti–6AI–4V) implants. Tissue–metal levels from revised cobalt–chromium implants averaged 45 µg/g dry tissue weight compared to 4,470 µg/g dry tissue weight from revised titanium–alloy implants, a 100–fold increase. Implant retrieval analysis showed severe burnishing and scratching in all titanium–alloy femoral heads and extensive burnishing and scratching in the majority of the femoral stems. Well–fixed cemented implants have similar low synovial fluid metal levels. However, when loosening of implants occurs, titanium–alloy implants release disproportionate levels of metal into synovial fluid and local tissues compared to stainless steel or cobalt–chromium.