The Fate of Delayed Unions After Isolated Ankle Fusion

Abstract

Category: Ankle Arthritis Introduction/Purpose: Despite advancements in surgical techniques, implants, and biologics, nonunion remains the most common major complication of ankle arthrodesis. While previous studies have reported delayed union or nonunion rates, few have elaborated on the clinical course of patients experiencing delayed union. We sought to better understand the trajectory of patients with delayed union by determining the rate of clinical success and failure and whether the extent of fusion on computed tomography (CT) was associated with outcomes. Methods: Delayed union was defined as incomplete ( < 75%) fusion seen on CT scan between 2 and 6 months postoperative. A total of 36 patients met inclusion criteria: isolated tibiotalar arthrodesis with delayed union. Patient-reported outcomes were obtained and patients were asked about satisfaction with their fusion. Success was defined as patients who were not revised and reported satisfaction with the procedure. Failure was defined as patients who progressed to revision or reported being not satisfied. Fusion was assessed by measuring the percent of osseous bridging across the joint on CT scan. The extent of bony bridging was categorized as absent (0%-24%), minimal (25%-49%), or moderate (50%-74%). Results: We determined the clinical outcome in 28 of the 36 eligible patients (78%) with mean follow-up of 5.6 years (range, 1.3 to 10.2 years). The majority (71%) of patients failed. A mean of 3.9 months (standard deviation, 1) elapsed between time of surgery and CT scan. Patients with minimal or moderate fusion on CT were more likely to succeed clinically than those with ‘absent’ fusion (X2 = 4.215, p = 0.040). Of those with absent ( < 25%) fusion, 11 of 12 (92%) failed. In patients with minimal or moderate fusion, 9 of 16 (56%) failed. Conclusion: We found that 71% of patients with a delayed union at roughly 4 months after ankle fusion required revision or were not satisfied. Patients with less than 25% osseous bridging on CT had an even lower rate of clinical success. These findings may help surgeons in counseling and managing patients experiencing a delayed union after ankle fusion.