<Li> polyethylene (originally Teflon), acetabular component, both of which were fixed to the bone using </Li> <Li> PMMA (acrylic) bone cement </Li> <P> The replacement joint, which was known as the Low Friction Arthroplasty, was lubricated with synovial fluid . The small femoral head (⁄ in (22.2 mm)) was chosen for Charnley's belief that it would have lower friction against the acetabular component and thus wear out the acetabulum more slowly . Unfortunately, the smaller head dislocated more easily . Alternative designs with larger heads such as the Mueller prosthesis were proposed . Stability was improved, but acetabular wear and subsequent failure rates were increased with these designs . The Teflon acetabular components of Charnley's early designs failed within a year or two of implantation . This prompted a search for a more suitable material . A German salesman showed a polyethylene gear sample to Charnley's machinist, sparking the idea to use this material for the acetabular component . The ultra high molecular weight polyethylene or UHMWPE acetabular component was introduced in 1962 . Charnley's other major contribution was to use polymethylmethacrylate (PMMA) bone cement to attach the two components to the bone . For over two decades, the Charnley Low Friction Arthroplasty, and derivative designs were the most used systems in the world . It formed the basis for all modern hip implants . </P> <P> The Exeter hip stem was developed in the United Kingdom during the same time as the Charnley device . Its development occurred following a collaboration between Orthopaedic Surgeon Robin Ling and University of Exeter engineer Clive Lee and it was first implanted at the Princess Elizabeth Orthopaedic Hospital in Exeter in 1970 . The Exeter Hip is a cemented device, but with a slightly different stem geometry . Both designs have shown excellent long - term durability when properly placed and are still widely used in slightly modified versions . </P>

When was the first total hip replacement done