Metal on Metal Hip Resurfacing: Current Indications and Results

Abstract

Hip resurfacing is a viable option in young patients suffering from an arthritic hip joint that is not amenable to joint preservation procedures. It offers an advantage over traditional hip replacement in terms of bone stock preservation. If the need arises, this preserves the option of performing a total hip replacement with sufficient bone stock in the proximal femur. The large diameter bearing surfaces articulate with low wear and extreme stability and minimal risk of dislocation. Recently concerns have also been raised about the occurrence of pseudotumors which are adverse tissue reactions to metal debris leading to significant soft tissue destruction. Although these lesions are relatively uncommon, they are often associated with malpositioned components (high abduction angle) and/or poorly designed acetabular components. Both excessive abduction and/or low arc of cover of the acetabular component predispose the bearing to edge loading and excessive wear with increased risk of soft tissue destruction. The current designs of hip resurfacing implants offer the option of using either a cemented or an uncemented femoral component mated with an uncemented acetabular component. The bearing surfaces are made of a cobalt-chrome alloy where a high carbon content is required for optimal wear properties.