Background: Subtalar arthrodesis is the surgical procedure commonly performed to treat subtalar arthritis. Subtalar arthrodesis may have a higher nonunion rate if there is a preexisting adjacent joint arthrodesis. The aim of this retrospective cohort study was to compare the subtalar arthrodesis union rate of patients with native tibiotalar joints to that of patients with prior tibiotalar arthrodesis. The secondary aim was to assess risk factors for nonunion. Methods: A retrospective cohort study of consecutive patients that underwent a subtalar arthrodesis in a single center between 2010 and 2020. The primary outcome of union was determined based on bridging callus on radiographs and clinical symptoms. If there was uncertainty, then a nonweightbearing CT was acquired. Chi-squared test and Mann-Whitney tests compared differences in demographics and risk factors for nonunion between groups. A logistical regression model was performed to determine risk factors for nonunion. Results: Eighteen patients had an adjacent ankle arthrodesis and 53 patients did not. The successful subtalar arthrodesis union rate in those with a preexisting ankle joint arthrodesis (44.4%) was approximately half that in those without an ankle joint arthrodesis (86.8%) ( P < .001). On multivariate logistic regression, an adjacent ankle arthrodesis was the only significant risk factor for nonunion. The odds ratio of nonunion of the subtalar joint with an adjacent ankle arthrodesis present was 4.90 (95% CI 1.02-23.56) compared to a subtalar arthrodesis with a native ankle joint. In addition, 9.4% of patients without an ankle arthrodesis underwent a revision subtalar arthrodesis compared with 44.4% of those with an adjacent ankle arthrodesis ( P = .001). Conclusion: In our study, we found that patients undergoing a subtalar arthrodesis with an adjacent ankle arthrodesis have a significantly increased risk of nonunion compared with those undergoing a subtalar arthrodesis with a native ankle. Patients with a previously fused ankle need counseling about the high risk of nonunion and potential additional surgery.

Background: Total talus replacements are a surgical treatment for talar avascular necrosis (AVN) replacing the entire talus. The potential for total talus replacements has increased with the advent of patient-specific implants using 3D printing based on computed tomographic scanning of the ipsilateral or contralateral talus. The primary aim of this review is to summarize the literature on total talus replacements, providing a historical survey, indications, controversies, complications, survival, and functional outcomes. Methods: A systematic review was performed. Articles with survival of total talus replacements were included. Basic percentages and a critical review of the literature was performed. Results: Nine articles with 115 patients were included. The mean age ranged from 27.6 to 72 years, but with 5 studies having a mean age of <50 years. Mean follow-up ranged from 12.8 to 152 months. The most common indication was avascular necrosis in 67 patients (58%). Five studies used customized implants and 4 studies used 3D printing. Four studies used ceramic prostheses, 3 cobalt chromium, 1 stainless steel, and 1 titanium with ceramic surface. Three studies involved a talus replacement in conjunction with an ankle replacement. Postoperative complications ranged from 0% to 33%. Of 24 functional outcomes scores, 66.7% demonstrated significant improvement. Conclusion: Total talus replacements are a promising alternative to tibiotalocalcaneal fusion for patients with avascular necrosis of the talus; however, further studies are required to ensure reliable outcomes prior to widespread adoption of this technology. Level of Evidence: Level IV, review of case series.

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.