CHICAGO — On balance, the news about joint replacement innovations for people with rheumatoid arthritis is good.
New lumbar artificial disks, new ankle implants, customized patient instrumentation, and computer-assisted surgical planning offer options that patients with RA-destroyed joints lacked even a decade ago. The unfortunate flip sides of these advances are aggressive and sometimes misleading direct-to-consumer marketing, and occasional unfavorable biological responses to even the newest implant materials.
The field of orthopedic surgery has benefited from “a lot of great science,” said presenter Dr. William Bugbee, an orthopedic surgeon with the Scripps Institute in La Jolla, Calif. Robust innovation has lead to “constant introduction of new technology.”
In the half century since British orthopedic surgeon Sir John Charnley pioneered modern total hip replacement, joint replacement has become one of the most common and successful interventions for arthritis, said Dr. Bugbee. Joint-specific arthroplasty is now available for hips, knees, shoulders, ankles, elbows, the small joints of the feet and hands, and the lumbar and cervical spines.
Spinal disk replacement is now an alternative to spinal fusion, although its efficacy is unproven, said Dr. Bugbee. The objective is to preserve motion, particularly in the cervical spine; for every level that is fused, the patient loses about 15% of motion. The levels above and below also come under greater stress and tend to degenerate.
Shoulder arthroplasties are often performed on patients with RA. The functional outcomes are acceptable and provide pain relief, but fall short of restoring normal shoulder function, said Dr. Bugbee. “Few people can play tennis” following shoulder arthroplasty, he said. The results depend on the integrity of the rotator cuff. A recent innovation is the reverse shoulder arthroplasty, which accommodates a deficient rotator cuff to allow better function of the shoulder after replacement.
Ankle arthroplasty remains the most common operation for arthritis, and is another area of new design. It presents a particular design challenge because the biological ankle has only 9 cm2 of joint surface and the cartilage is 1 mm thick. The joint requires congruity and endures high contact stress. There are multiple new implant designs.
Arthroplasties of the hip and/or knee have become common and successful surgical interventions for arthritis, and the need for them is growing with the population. It has been estimated that by 2030, the U.S. population will need 2.3 million knee replacements per year. “There's not enough manpower to do all that work,” said Dr. Bugbee. Technical skill is the single most important factor in success.
The appropriate patient age for joint replacement now ranges from the 40s through the 90s said Dr. Bugbee. Although the intervention was originally conceived to relieve pain for elderly, low-demand patients, it is now expected to bring both pain relief and functional improvement. But it is not without risk: Dr. Bugbee estimated that 90-day mortality after surgery is less than 1%, but deep vein thrombosis occurs in 10%-40% of cases. Dislocation rates are 0%-10% because of larger ball and socket joints. Dr. Bugbee estimated that infection occurs in 0.3%-3% of operations.
There are also functional limitations after joint replacement. “A good hip replacement is tantamount to a normal joint,” said Dr. Bugbee. “Unfortunately, the knee is not the same. It is a much more complex joint.”
One area of concern is biological response to implant materials. Microscopic wear debris can be shed by the articulating surfaces. The polyethylene plastic in some implants can cause a granulomatous response, and an osteolytic response in the bone. In metal-on-metal joints, a tiny amount of wear debris may cause severe early osteoarthritis. Ceramic-to-ceramic hip joints have a wear rate about 50 times less than that of conventional polyethylene joints, but they may squeak.
Direct-to-consumer advertising campaigns have promoted minimally invasive surgery, but smaller incisions are not correlated with better outcome, said Dr. Bugbee. They may even have a higher complication rate.
“The next innovation is so-called customized patient instrumentation,” said Dr. Bugbee. The surgery can actually be computer modeled in advance, and can incorporate instruments that are custom built to fit the individual patient's joints. The surgery is then more accelerated and more precise.
Moderator Dr. John J. Cush of Baylor University Medical Center in Dallas, asked, “When patients have bilateral knees, or right and left knees, one of the things I've noticed over the years [is that] they'll always say, ‘My right (or my left) is the best one.’ They always have an ipsilateral evaluation and a preference. Is there a good reason for that?”
“No. I've seen the same thing. I cannot for the life of me figure it out,” said Dr. Bugbee.
http://www.rheumatologynews.com/article/S1541-9800(10)70306-9/fulltextGood stuffI wonder if the preference to right or left after bilateral replacements is due to the patient being right or left side strong?