Fixation of total knee replacement : Effects of bone specific drugs and tourniquet use

Knee and hip replacements are among the most common surgical procedures in today's healthcare. Joint replacement is effective for treating pain and disability from osteoarthritis. Although most patients are satisfied with their operation, two percent are reoperated within two years. A common cause for reoperation is aseptic loosening. Almost three thousand reoperations of hip and knee prostheses are performed annually in Sweden. The most common reason for a reoperation is aseptic loosening. Such interventions are technically difficult, associated with poor patient satisfaction, greater risks of complications, and involving larger costs for society. The primary mechanism of aseptic loosening is debated, but it has been convincingly shown that a well-fixed implant in the first two years after the operation is important for the long-term survival of the prosthesis. Even well-integrated prostheses can loosen over time if the fixation is impaired. The use of a tourniquet, to obtain a bloodless field in knee replacement surgery is very common but can have serious side effects. The bloodless field during the operation theoretically creates a blood-free bone bed for cementation, which might lead to better fixation because the bone cement can penetrate into the trabecular bone structure. In this thesis, we show that surgery performed with tourniquet did not improve fixation but may cause more postoperative pain and decreased range of motion (Study I). We also explored using bone specific drugs to improve fixation: parathyroid hormone (Study II) stimulates bone-forming cells (osteoblasts), and denosumab (Study III) inhibits bone-resorbing cells (osteoclasts). We found that patients who received parathyroid hormone after total knee replacement did not experience improved fixation, whereas those treated with denosumab showed enhanced fixation. Similar to denosumab, bisphosphonates—widely used in the treatment of osteoporosis—also inhibit osteoclast function. Study IV is a p