Joint Distraction Surgery for Ankle OA
Repairing, not replacing, joints may be the next step in osteoarthritis care.
Treatment for hips and knees worn down by arthritis is usually straightforward: joint replacement surgery. But surgical solutions for osteoarthritis in the ankle are less clear-cut. Joint distraction arthroplasty (JDA) may offer the best solution.
Traditional repair methods such as fusion – or arthrodesis – require bones in the ankle and leg to be permanently locked together with plates and screws. Pain relief can be dramatic, but it comes at a price: an abnormal gait, potential arthritis in nearby joints and an ankle too immobile for sports or climbing stairs.
The alternative is an artificial joint, similar to a hip or knee implant. Ankle replacement is more complicated though, and requires a high degree of surgical skill. Ankle implants also tend to wear out quickly, making them a poor choice for the younger, more-active patients who often need them.
"Most people with knee arthritis are in their 60s and thinking about retirement, whereas ankle arthritis frequently strikes people in their 40s who need to function and provide for their families," explains Gregory C. Berlet, MD, an orthopaedic surgeon at the Orthopaedic Foot and Ankle Center in Columbus, Ohio.
A Better Option for Younger Patients?
Some doctors advised younger patients to grin and bear it until a better option comes along. But one exists. JDA uses the body's natural repair mechanisms to heal the joint without damaging it.
It involves pulling the joint surfaces slightly apart and holding the bones in place with pins set in an external fixation frame. The theory is that the absence of mechanical stress on the joint combined with changes in intraarticular fluid pressure allows damaged cartilage to repair itself, explains Austin T. Fragomen, MD, director of the Limb Lengthening Clinic at Hospital for Special Surgery (HSS) in New York City.
HSS physicians have used distraction arthroplasty for ankle arthritis for a decade and recently began using it for knees.
Surgeons remove any bone spurs – growths common in ankle arthritis – and drill small holes in the bone (called microfracture) to help stimulate cartilage repair. Then assemble the frame, about six inches in diameter, that encircles the ankle like a halo. It stretches the joint surfaces about 5 millimeters – less than a quarter inch. Stem cells from the patient's bone marrow are used to jumpstart the repair process. Because they can transform into cartilage cells, stem cells are often used in orthopaedic surgeries.
Patients wear the fixation frame, which Dr. Fragomen admits is bulky and apt to "tear the sheets," for about three months then switch to a temporary walking boot. Full recovery takes close to a year. By then, a thin layer of new cartilage has formed, bone swelling is reduced and subchondral cysts – fluid-filled sacs that are common in osteoarthritis – have been absorbed.
Dr. Fragomen says, " The goal is for patients to be able to get out of bed and walk and stand for prolonged periods – to walk the dog or go hiking. And in 75 percent of cases, they can. That the procedure has a 75 percent success rate is supported by five different studies."
It's not known why distraction fails in about a quarter of treated patients. "Some of it is biology; the bone simply doesn’t respond," Dr. Fragomen notes.
It's also not clear who is best suited for the procedure.
"Distraction arthroplasty was developed for young people, but I've had patients over 60 who wanted to try it," Dr. Fragomen says. "And we found that older patients actually scored highest on functional measures. So we try not to exclude too many people who could benefit."
Anyone with a functional range of motion is a candidate, including patients with post-traumatic arthritis, which develops years after a fracture or other injury. Distraction is not an option for people who lack all ankle motion or have advanced inflammatory arthritis.
The most common complication is an easily treated infection at one of the pin sites. Severe pain, Dr. Fragomen says, is rare.
The benefits of distraction arthroplasty last at least 10 years – the amount of time HSS has followed patients. If symptoms recur, the process can be repeated. Or, if ankle implants continue to improve, replacement surgery may eventually become a satisfactory option for younger patients.
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