New Treatment on the Horizon for Ankle ArthritisLittle by little orthopedic surgeons are finding better ways to treat ankle arthritis besides just fusing the joint. In this report, the use of a new technique called distraction arthroplasty for ankle arthritis is presented. It is one more step in the direction of preserving joint motion, especially in young patients.
Distraction arthroplasty is done by using an external frame with rods that stretch the ankle apart. The frame looks like a circular cage around the ankle and lower leg. A thin wire is placed through the joint and acts as a guide wire until the device is fully in place. Then the wire is removed.
The patient ends up with a cage that has two rings (one at the top, one at the bottom) and two rods in between the top and bottom rings. The rods are lengthened a little bit at a time pulling the joint apart. The joint only separates a tiny amount (up to three millimeters which is about one tenth of an inch).
What's the theory behind how this works? Scientists working in the lab have found that chondrocytes (cartilage cells) damaged by trauma can actually recover or produce new cells.
By distracting or separating the joint, pressure is changed in the joint. The patient is allowed to walk on the leg and put weight on the foot. Being on and off the foot creates an intermittent (comes and goes) hydrostatic (fluid) pressure. Chondrocytes seem to respond to this effect and form new, healthy cells.
Who would have thought that stretching a joint while at the same time putting weight on the leg would improve cartilage? But that's what's happening. There's actually a bit more to the procedure. Before applying the distraction device, the surgeon must clean out the joint, repair any damage done to the ligaments or other soft tissues, and restore normal ankle joint alignment.
There's no sense in stimulating new chondrocytes that are just going to get chewed up and destroyed. Abnormal joint alignment and deformities that aren't corrected cause uneven load bearing surfaces in the joint. Without correction of these problems, the new cartilage will get worn down same as before.
The natural questions to ask are: how well does this work? How long does it take? And who can benefit from this procedure? There aren't a lot of published studies to help answer these questions. What is known so far is based on small studies with only 20 to 24 patients.
Pain is reduced and function improved in the majority of patients. The results seem to hold for up to two years. Long-term results (beyond two years) from most studies done just aren't available yet. There are some patients who end up with additional surgeries and complications like infection. Quite a few patients have continued pain and discomfort.
Patients may not see any improvement at first. But after six months' time, the positive benefits of the procedure become more evident. When compared with patients who just have the cleaning out procedure called debridement, the distraction patients do much better.
The authors say that it's possible the deformity correction would have been enough to yield the positive results attributed to the distraction arthoplasty. It's really hard to tell without two separate groups -- one treated with deformity correction alone and the other with deformity correction and distraction arthroplasty.
That brings us to the question of who can benefit from the distraction arthroplasty procedure? Right now, it looks like younger patients who still have a fairly mobile ankle joint are better candidates than older adults with a stiff joint.
For anyone with ankle arthritis, the options are debridement, deformity correction, fusion, joint replacement, and now distraction arthroplasty. It's not always clear which approach to take. More studies comparing treatment results among the various options are needed. Identifying which treatment works best for patients will take some time but will be worth the wait.
Matt Harrison and Douglas Beaman. Treatment of Ankle Arthritis with Distraction Arthroplasty. In Current Orthopaedic Practice. May/June 2010. Vol. 21. No. 3. Pp. 229-232.
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