Outcomes of Total Ankle Replacement are Worse in Patients with Ipsilateral Hindfoot Fusion

Abstract

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: Hindfoot (subtalar and/or talonavicular) fusion is a commonly used procedure to treat arthritis and/or deformity. As a result, some patients with ankle arthritis who undergo total ankle replacement (TAR) have a history of prior hindfoot fusion or undergo concomitant hindfoot fusion at the time of TAR. Previous studies have demonstrated hindfoot fusion as a risk factor for failure of TAR and associated with worse clinical outcomes. This study seeks to determine if these findings are reproducible by evaluating clinical and patient-reported outcomes (PROs) of primary TAR with ipsilateral hindfoot fusion at a minimum 2-years follow-up from primary TAR. We hypothesized that TAR patients with ipsilateral hindfoot fusion would have higher rates of revision and worse PROs compared to controls. Methods: A retrospective review of prospectively collected data within an institutional registry was performed. Inclusion criteria for this study were patients undergoing primary TAR (Cadence, Inbone, Invision, Infinity, Salto, Vantage, or Zimmer) between October 2015 and January 2022, with or without prior/concomitant ipsilateral hindfoot fusion, with preoperative and 2-year postoperative PROMIS scores. 400 TARs met inclusion criteria for analysis. Demographic, clinical, patient-reported outcomes, and radiographs were collected. Radiographic complications (including cysts, lucency, subsidence) were recorded. Multivariate linear regression models were used to evaluate the associations of hindfoot fusion, implant type, reoperations (defined as any surgical procedure following primary TAA, including retention of metal implants with polyethylene explant), revisions (defined as exchange of tibial and/or talar components), and demographics with 2-year postoperative PROMIS scores. Finally, proportions of patients meeting PROMIS thresholds for the patient-acceptable symptom state (PASS) at 2-years postoperative was compared between groups via Pearson Chi square tests. Results: Of 400 ankles included, 49 (12.3%) had ipsilateral hindfoot fusion. In multivariate analysis, hindfoot fusion patients had significantly worse 2-year postoperative PROMIS scores in all domains (except depression) versus patients without hindfoot fusion. Preoperative PROMIS domains were predictive of 2-year postoperative PROMIS scores for each respective domain (except pain intensity) (Figure). Hindfoot fusion patients had a significantly higher rate of revision (10.2%) than those without hindfoot fusion (2.6%) (P=0.038). However, reoperations were similar between groups (9.7% versus 12.2%, P=0.460). Additionally, the incidence of radiographic complications was not significantly different between groups (P=0.075). Hindfoot fusion patients were equally as likely to meet PASS thresholds at 2-years postoperatively in all domains except global mental health (P=0.015) and depression (P=0.024). Conclusion: This study demonstrates that TAR patients with ipsilateral hindfoot fusion experience worse pain, function, and physical and mental health postoperatively compared to their counterparts without ipsilateral hindfoot fusion. Although hindfoot fusion may be critical to achieving a stable, neutrally aligned ankle and hindfoot, hindfoot fusion may increase the risk for worse patient-reported TAR outcomes. As indications for TAR continue to expand, it is imperative to understand the role of hindfoot fusion in the survivorship and function of TAR to guide clinical decision making and patient education for establishment of postoperative expectations.