Arthritis Today—April 23, 2013
Knee implants in young people with juvenile idiopathic arthritis (JIA) are durable – but don’t last quite as long as implants in older arthritis patients, according to a multicenter study led by researchers at Hospital for Special Surgery (HSS) in New York. Although about 90 percent of knee replacements last 15 to 20 years in adults, about 75 percent of knee implants last that long in patients with JIA. The research was presented recently at the 2013 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS).
JIA is an umbrella term for a group of potentially debilitating conditions affecting the joints in children and adolescents. Although new medications and treatment protocols have improved the prognosis for many JIA patients, surgery is sometimes needed to replace a severely damaged joint. Because joint replacement in the very young is relatively rare, little is known about long-term outcomes.
"Most studies [on joint replacement in JIA patients] have been small with short-term follow-up," says Mark P. Figgie, MD, senior study author and chief of the Surgical Arthritis Service at HSS. "And none have been used to take the next step for these kids, which is to find out what we can do to make things better for them."
To help take that next step, Dr. Figgie and colleagues assessed the longevity of total knee replacement in an international group of patients with JIA. The study included 217 people who had undergone a total of 335 knee replacements at five hospitals between 1979 and 2011. Participants ranged in age from 11 to 58, with an average age of 28 at the time of surgery. The average follow-up was nearly 13 years, with a range of 2 to 33 years.
Results showed that the 10-year survival rate of knee implants among JIA patients was 92.2 percent. The 20-year implant survival rate was a little more than 75 percent. Dr. Figgie, who is also a professor of clinical orthopaedic surgery at Weill Cornell Medical College in New York City, says he is concerned by the numbers because implants in children need to last longer. "When you put a new knee in a 20 year old, it has to last a long time. If our numbers were similar to adults' – a 90 percent implant survival rate at 15 to 20 years – that still wouldn't be great [for kids] because we would still be revising 1 in every 10 knees within 15 to 20 years," he says.
Revision surgeries, in which a failed implant is removed and replaced, are technically challenging and frequently less successful than the original operation.
Dr. Figgie notes that several factors likely affect the longevity of implants in JIA patients.
"I've tried to figure out why these implants failed, and I would say that in the 1980s and '90s, we were treating the worst cases," he says. "Our patients were on a lot of steroids, their bone quality was poor and deformities could be terrible. Many were in a very debilitated state by the time they came to us because no one wanted to operate on a 15- or 16-year-old. Now, there are better drugs and patients are functioning at a much higher level, and they tend to do better."
He adds that the standard implants typically used in young patients pose problems, too. "What I've seen over the years is that standard implants don't fit very well because of unusual deformities in bone shape and size. Arthritis causes the growth plate to grow abnormally, so we tend to custom fit many of the implants [for young patients]. The better the implant fits, the better it should function and the longer it should last. The problem now is that custom implants are much harder to get because of new FDA regulations." And, they are also five or six times more expensive than standard ones.
In addition to implant longevity, the study also looked at function while performing daily activities, such as walking and climbing stairs. Nearly half of participants could walk without restrictions, most could manage stairs and only a small number used a wheelchair.
Dr. Figgie says the purpose of the study was to make people aware of the difficulties inherent in treating JIA patients. "This is a challenging patient population with specific, and, I feel, unmet needs," he explains. "Standard implants may or may not be the best solution, so it's important to look at how well they've survived and functioned. Then we have to figure out why they failed and what we can do in the future to improve them."
This article originally appeared on arthritistoday.com.
Read the news release.
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