Subtalar Arthrodesis Union Rates With and Without Adjacent Ankle Arthrodesis

Background: The tibiotalar arthrodesis for end-stage ankle osteoarthritis is a surgical procedure that leads to a modification of the kinematics of the adjacent joints and may result in the development of secondary osteoarthritic degeneration of the subtalar joint. It has previously been observed that subtalar arthrodesis in this context shows a lower fusion rate than isolated subtalar arthrodesis. This retrospective study reports the results of subtalar joint arthrodesis with previous ipsilateral tibiotalar arthrodesis and suggests some factors that may compromise the fusion of the joint. Methods: Between September 2010 and October 2021, 15 arthrodeses of the subtalar joint with screw fixation were performed in 14 patients, with a fusion of the ipsilateral tibiotalar joint. Fourteen of 15 cases used an open sinus tarsi approach, 13 were augmented with iliac crest bone graft, and 11 had supplemental demineralized bone matrix (DBM). The outcome variables were fusion rate, time to fusion, and revision rate. Fusion was assessed by radiographs and computed tomography scan. Results: Twelve of the 15 subtalar arthrodeses (80%) fused at the first attempt with an average fusion time of 4.7 months. Conclusion: In this limited retrospective case series, compared to the fusion rate of isolated subtalar arthrodesis reported in the literature, the rate of subtalar fusion in the presence of an ipsilateral tibiotalar arthrodesis was found to be lower. Level of Evidence: Level IV, retrospective case series.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Subtalar Arthrodesis in Patients With Prior Tibiotalar Arthrodesis for Posttraumatic Osteoarthritis

Theunissen

Birch

Reymond³

et al. 2023

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confidence: 96%

“…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…”

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confidence: 99%

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

Davies¹,

Jennison²,

Dalgleish³

et al. 2023

Self Cite

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.

“…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:…”

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confidence: 98%

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

Pattisapu¹,

Michalski²,

Pfeffer³

2023

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.