Characteristics of nonunion after arthroscopic ankle arthrodesis: A multi-center retrospective cohort study

Background: Nonunion is a major complication of arthroscopic ankle arthrodesis. However, the characteristics and risk factors of nonunion are not well understood. This retrospective multi-center observational study aimed to clarify the characteristics of nonunion after arthroscopic ankle arthrodesis. Methods We included 154 patients who underwent arthroscopic ankle arthrodesis at one of five institutions. Patients were divided into two groups: union and nonunion, and the groups were compared. Age, sex, body mass index, diabetes, smoking, corticosteroid use, diagnosis, treatment information, treatment protocol, radiographic evaluation, and patient-reported outcomes were recorded and analyzed. Results On radiographs, bony union was observed in 142 ankles (91.0%) but not in 12 ankles (9.0%). Postoperative radiographic tibial bony gap (mm) was significantly larger in the nonunion group (medial = 1.98, center = 1.65, anterior = 2.21, middle = 1.72, posterior = 3.01) (mm) compared to the union group (medial = 1.35, center = 1.13, anterior = 1.28, middle = 1.03, posterior = 2.03) (mm). Furthermore, the visual analog score (VAS) of pain and pain-related self-administered foot evaluation questionnaire (SAFE-Q) subscale score significantly worsened in the nonunion group (VAS = 3.83, SAFE-Q subscale score = 69.8) than in the union group (VAS = 1.35, SAFE-Q subscale score = 76.6). Conclusion A larger radiographic tibiotalar bony gap was observed in the nonunion group. Other measurement outcomes were not associated with nonunion. Additionally, patient-reported outcomes markedly worsened in the nonunion group.