Acrylic cement stabilized joint replacements

Abstract

Surgical management of osteoarthritis, aseptic necrosis and rheumatoid arthritis has been revolutionized by the introduction of acrylic cement-stabilized joint surface replacement. Although single joint surface replacements have been employed extensively for more than half a century, total surface replacement operations with a wear-resistant high-density polyethylene and noncorrosive stainless steel stabilized by acrylic cement were introduced only a little more than 12 years ago. This evolved with Charnley's discovery of the high level of bone tolerance for acrylic cement. Acrylic cement made it possible mechanically to bond artificial joint surfaces to the bone ends and produce an insensitive Charcot-like functioning joint. A barium sulfate additive makes the cement radiopaque for visualizing the bone-cement interface. Barium sulfate additive also lowers the polymerization temperature and opens the polymer for influx of interstitial fluids. Antibiotics have also been added to the cement for prevention and treatment of infection of the surrounding tissues. In aged individuals with cardiovascular disease, the absorption of the acrylic monomer depresses cardiac output and produces hypotension for 2-5 minutes after impaction of acrylic cement into spongy bone. The hypotension has been minimized by cautious fluid replacement and maintenance of adequate blood volume before, during and after the operation. Approximately 30,000 total hip arthroplasties are performed in the United States annually in patients older than 50 years of age with fractured femoral head replacements, bilateral rheumatoid arthritis, old neglected congenital dislocations of the hip or osteonecrosis with and without osteoarthritis. The pain relief is more complete and the functional improvement more predictable than in any other previously recommended surgical operation for the purpose. For this reason, total hip arthroplasty has almost completely supplanted mold-arthroplasty, osteotomy, capsulotomy (hanging hip) and resection of the femoral head. Hemiarthroplasty in the form of femoral head replacement still is the procedure of choice in patients with fractures of the neck of the femur and a normal acetabular articular cartilage, irrespective of age. As a countermeasure against loosening of the prosthesis in patients with osteoporosis and a hollow proximal end of the femur, the stem can be stabilized with acrylic cement. A standard replaceable femoral head for subsequent conversion of femoral head replacement to total hip arthroplasty is an important consideration and presently is under investigation in several medical centers.(ABSTRACT TRUNCATED AT 400 WORDS)