Acrylic cement stabilized joint replacements.

Summary 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 sulface 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. The reconstruction of neglected congenital dislocations of the hip in adults is a remarkable by-product of the past 2 years of experience with total hip arthroplasty; it now is possible to excise the periarticular tissues, lengthen the lower extremity and transfer the proximal end of the femur from the position of a false to true acetabulum fitted with a high-density polyethylene socket and stainless steel femoral head. John Charnley, the innovator of the prototype of present designs of high-density polyethylene and stainless steel total joint replacement, introduced clean air operating rooms as a supplement to aseptic technic. Reasoning that total joint replacement exposes a large surface area of potentially contaminated tissue and introduces a very large volume of foreign material into the interior of the innominate bone, Charnley devised a special clean air enclosure for his operating room. Later, he added equipment to separate the respired air of the operating room personnel, including the patient, from the room air flowing over the wound. Many designs and improvements in clean air operating rooms have been made in recent years. Statistical evidence, however, for the principle of special clean air operating rooms is as yet incomplete. Also unproved by statistical evidence, and requiring a doubleblind prospective study, are prophylactic antibiotics and local antibiotics in irrigating solutions throughout the operation. All of these measures are nevertheless presently applied by the majority of surgeons in the United States. There are many variations in the technic of total joint arthroplasty. The most important is osteotomy of the greater trochanter for exposure of the acetabulum. Beginners in the field generally are advised to employ the Charnley transtrochanteric route first because it is a necessary measure for deformed hips and for nearly all revision operations. For treatment of primary osteoarthritis, the posterolateral approach without osteotomy of the trochanter provides ample exposure, is relatively bloodless and avoids problems of reattachment and healing of the greater trochanter. Considering the large number of patients currently requesting total joint arthroplasty, complications are relatively few but these may be so serious and wide in variety that specialists in all fields of medicine and surgery are being called on for assistance. Patients generally are referred for medical and surgical survey work for the specific purpose of preoperative examinations for cardiovascular, genitourinary, foci of chronic infection and other areas of anticipated complications. Either systemic or biomechanical (or a combination of the two) complications are the only real source of patient dissatisfaction with total hip arthroplasty. The systemic complications are thromboembolic disease, femoral neuropathy and infection. Biomechanical complications are loosening of the implant at the bone-cement interface, fractures of stems of the femoral prosthesis and wear erosion. The combined biologic and mechanical complications are periarticular ossification, bladder fistula and false aneurysms from spillage of cement through defects in the inner table of the pelvis. Case reports now can be cited to demonstrate that deep infections may originate from a source remote from the wound and sometimes become active several years after the operation. As the life expectancy of patients with total hip arthroplasty increases and as the patients in younger age groups become candidates for this surgical treatment, physicians are bound to encounter increasing numbers of patients with biomechanical complications, such as wear erosion, loosening and stem fractures. Statistics on the results of total hip arthroplasty now are based on a significant number of patients examined by carefully standardized methods over periods of 5–10 years in the United States and 10–12 years in the United Kingdom as well as many other parts of the world. Although there are many different designs of high-density polyethylene-to-metal articulating surfaces for total hip arthroplasty, the results generally are about the same. The results are 75–85% relief from pain, 65–75% improvement in gait and 30–50% significant improvement in range of mobility. The relief from pain is the most remarkable and predictable benefit from the operation. Hip arthroplasties with metal-to-metal articulating surfaces with and without cement fixation have been reported in statistically significant numbers but the percentages of excellent results are somewhat lower. In a series of case reports on 3480 patients investigated under the auspices of the U. S. Food and Drug Administration, the acrylic cement for stabilization of total hip arthroplasty was approved on the basis of 83% very good or excellent results. The series included only 1.6% of posoperative complications. Although the number of cases is not nearly as great as of the hip joint, the principles of total hip arthroplasty have been applied to the knee joint with considerable success in selected cases. The indications are bilateral destructive degenerative disease, e.g., rheumatoid arthritis, ankylosing spondylitis, osteoarthritis with subchondral destruction of bone with varus and valgus deformities in patients on crutches. Total ankle arthroplasty for osteonecrosis or ankylosis, metatarsophalangeal joint arthroplasty for hallux valgus, shoulder joint arthroplasty for extensive destructive lesions of the glenohumoral joint, total elbow arthroplasty for bilateral ankylosis, total wrist arthroplasty for grotesquely deforming rheumatoid arthritis and flexible interphalangeal joint implants for osteoarthritis and rheumatoid arthritis are all now undergoing intensive investigation. Most of the new designs of total joint arthroplasty, other than designs for the hip and knee, are described mainly in manufactures' pamphlets and are only just beginning to appear in surgical journals. Biomechanists and engineers collaborating with manufactures and orthopedic surgeons now are testing new materials for improvements in the long-term wear properties of all kinds of joint surface replacements of the human skeleton. This new field of surgery is growing with extraordinary rapidity yet with unprecedented consideration for the needs of individual disabled patients.