Years ago I had to choose between an ankle fusion and an ankle replacement. The implants used in the replacement were fairly new and unpredictable. So I went with the fusion. I've always wondered if I made the right choice. What's the status of ankle replacement these days?
Years ago, surgeons asked the question: joint replacement has worked for the hip, knee, shoulder, and hand -- why not for the ankle? It could spare ankle motion and would certainly be better than a fusion with no motion. But early attempts failed. The ankle is just so much more complex in its biomechanical design than even the shoulder.
So it was back to the drawing board. And now there's a second-generation of implants that seem to have better results. Second-generation refers to the new and improved designs that have replaced those first implants. The studies available are somewhat limited, but it looks like there are fewer problems and a lower rate of failures with the newer ankle prosthetics.
The modern implant design tries to reproduce sliding, gliding, and rotational movements present in the natural ankle. By experimenting with different coatings sprayed on the implant, researchers have found materials that preserve bone and foster improved bone growth around the implant. With better ingrowth, cement is no longer needed to hold the implant in place. That helps eliminate problems caused by the use of cement.
Improved polyethylene (plastic) parts have also improved movement between the parts and reduced overall wear on the implant. That means they are less likely to break or shift causing a partial or complete joint dislocation.
Implants are expected to last at least five years. Some studies show fair-to-good survival rates at 10 years. Slow healing and fracture of the ankle bone are the two main problems that develop. There's evidence to suggest that these problems are less common as the surgeon's level of experience increases.
Sometimes the implant migrates (moves) or sinks down into the bone (called subsidence). That doesn't always mean the implant is a failure. Many patients still report great improvement over their pre-operative state of severe pain and loss of function. They can move their ankle through a greater arc of motion. And they can walk with a normal or near-normal gait pattern. Some even participate in sports.
There are a few studies comparing the long-term results of fusion versus joint replacement. It's a little bit like comparing apples to oranges. Reasons for failure or the need for revision surgery differ. But the rate of amputation for a failed procedure has been less (one per cent) in patients with ankle replacement compared with five per cent of patients with ankle fusion. All other things being equal, it looks like the results are fairly equal between these two treatment options.
Praveen Yalamanchili, et al. Total Ankle Arthroplasty: A Modern Perspective. In Current Orthopaedic Practice. March/April 2009. Vol. 20. No. 2. Pp. 106-110.
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