Letter Regarding: Subtalar Arthrodesis Union Rates With and Without Adjacent Ankle Arthrodesis

Abstract

We enjoyed reading the article by Jennison et al regarding the rate of subtalar fusion following ankle arthrodesis. 2 However, we have some questions and concerns regarding the methods and conclusions of this study:The authors inconsistently obtained computed tomography (CT) scans to assess for nonunion. The authors noted that they obtained CT scans on patients with inconclusive clinical and radiologic assessment. The authors do not mention how many CTs were obtained and do not describe when advanced imaging was obtained.Without CT scans to document successful unions, it is impossible to meaningfully compare the 2 groups. Patients with isolated subtalar fusions are far less likely to have symptoms than those who have combined ankle and subtalar fusions. Therefore, patients in the combined fusion group would have been sent for a CT in greater numbers, given that one of the indications for a CT was continued symptoms. CT studies would have further elucidated the nature of suspected nonunions, that is, which suspected nonunions had achieved partial or full nonunions or symptomatic unions. 3,4 The authors' radiographic assessment of union and progression to weightbearing both appear premature. The authors progressed their patient's weightbearing status postoperatively solely based on their assessment of radiographic union on anteroposterior and lateral radiographs at 6 weeks. Six weeks postoperation is an early time point to assess radiographic union. Davies et al 1 waited 12 weeks postoperatively to progress weightbearing and assess union via radiographs.The authors finish their study arguing for ankle replacement over ankle arthrodesis. The authors write, "This information may also inform the debate currently occurring regarding preservation of ankle joint motion with replacement rather than arthrodesis for end-stage ankle arthritis." We feel that the authors' data do not support this. The study does not evaluate subtalar fusion rates following ankle replacement vs fusion, and the authors lack clear CT imaging, which would clarify their "nonunions."Identifying the rate of subtalar nonunions in patients with prior ankle fusions presents a challenging clinical question. Further research with consistent CT studies is needed to answer this fully.