Foot & Ankle

Ankle arthroplasty in the stiff ankle?

One of the great unanswered questions in ankle arthritis is “What are the indications of ankle arthroplasty in patients with a stiff ankle?”. The Foot & Ankle Group in Dallas, Texas (USA) turned their attention to this difficult problem.⁵ The authors note that the two competing approaches (arthroplasty and fusion) have very different effects on the biomechanics of the foot and ankle. Traditionally, ankle arthroplasty has been thought of as a motion-sparing rather than a motion-producing procedure and, as such, has not really been considered an option in ankles that are already stiff. There are obvious potential advantages of ankle arthroplasty over fusion, including sparing of the subtalar joint from arthrosis, and maintenance of more normal gait biomechanics over fusion. However, these benefits are debatable in their magnitude, and should be offset against the downsides of long-term longevity and difficulty of revision. The current study investigates the hypothesis that there would be improvements in parameters of gait with ankle arthroplasty, even in patients with a low degree of pre-operative total sagittal range of motion. The authors conducted a retrospective review of 67 patients who underwent total ankle arthroplasty for end-stage ankle arthritis and in whom over a year’s worth of follow-up data was available. The authors recorded a variety of demographic, surgical, and gait analysis data, with the aim of establishing the determinants of a more normal gait using multivariate analysis. As perhaps would be expected, a greater degree of pre-operative sagittal range of motion was predictive of greater post-operative sagittal range of motion. What is most surprising, however, is that patients with limited pre-operative range of motion experienced a greater overall improvement in range of motion, as well as clinically meaningful absolute improvements in range of motion, and other parameters of gait. The authors conclude that “On one hand, a low preoperative range of motion resulted in a lower absolute postoperative function. On the other hand, patients with stiff ankles preoperatively had a statistically and clinically greater improvement in function as measured by multiple parameters of gait.” It certainly seems to us here at 360 that, based on these results, we may need to think again about the supposition that pre-operative stiffness precludes ankle arthroplasty, as here there are marked benefits to report.