Response to “Letter Regarding: Subtalar Arthrodesis Union Rates With and Without Adjacent Ankle Arthrodesis”

Abstract

We would like to thank Dr Pattisapu and colleagues for their interest in our article on subtalar arthrodesis rates, dependent on the presence of an adjacent ankle arthrodesis or not. 1 This is a retrospective cohort study designed to either confirm or refute our clinical suspicion that patients who had undergone a previous ipsilateral ankle fusion had a higher rate of subtalar nonunion than those patients without an ankle arthrodesis. Clearly, as this was a retrospective study, CT scans were only available for those patients who were symptomatic and had signs of nonunion. From a pragmatic perspective, there is no benefit in performing a CT scan in an asymptomatic patient. Pragmatism prevails in poorer-resourced health care systems across the globe. Therefore, it would be our usual practice to obtain CT scans in patients of concern at a minimum of 6 months postsurgery.Dr Pattisapu and colleagues state that "patients with isolated subtalar fusions are far less likely to have symptoms than those who have combined ankle and subtalar fusions."We have not found this to be the case and therefore disagree that this group would be subject to higher rates of CT scanning, thereby artificially increasing the nonunion rate in patients with ipsilateral ankle and subtalar fusions.It is our usual practice to mobilize all hindfoot and ankle arthrodesis patients at 6 weeks in a removable boot. Although radiographs are obtained at this stage, they are used to ensure that there has been no significant shift or failure of the hardware or construct. We would not expect to see bone union at this stage, and it is not looked for.Ultimately, this study demonstrates that there are higher rates of subtalar nonunion in patients with ipsilateral ankle arthrodesis than those without. We would, therefore, contest Dr Pattisapu's point that we have not added to the debate on ankle arthrodesis vs ankle replacement in patients requiring subtalar fusion, when the literature has shown higher rates of subtalar union in patients with arthroplasty 2 compared to our series of fused ankles.Finally, we would very much like to agree that identifying the rates of subtalar fusion in patients with or without ankle arthrodesis is challenging and we would very much welcome the results of a prospective randomized controlled trial with computed tomography-proven union as an endpoint.