Factors Associated with Nonunion and Infection Following Ankle Arthrodesis using a Large Claims Database

CATEGORY: Ankle; Ankle Arthritis INTRODUCTION/PURPOSE: Complications such as nonunion and infection following ankle arthrodesis can lead to increased patient morbidity and financial burden from repeat operations. Improved knowledge on complication likelihood and associated risk factors can improve patient selection and inform post-ankle arthrodesis surveillance protocols. METHODS: This is a large retrospective, database study with structured query of a national insurance claims database (PearlDiver Technologies) for patients treated with ankle arthrodesis from 2015 through 2019 as identified by ICD-10 codes. Patients with any operation one year prior to or following ankle arthrodesis were excluded from analysis to prevent attributing complications to another operation. Likelihoods of nonunion and infection within one-year and three-years following ankle arthrodesis were analyzed using Kaplan-Meier estimations. Patient characteristics associated with the identified complications following ankle arthrodesis were analyzed using multivariable logistic regression analyses; data included age at time of operation, sex, obesity, smoking record, diabetes, and the Elixhauser Comorbidity Index score. RESULTS: Our query yielded 2,463 patients in the five-year period who underwent ankle arthrodesis. Nonunion occurred in 11% (95% CI, 10-12) of patients within one-year of ankle arthrodesis and 16% (95% CI, 14-17) of patients within three-years. Infection occurred in 3.9% (95% CI, 3.1-4.7) of patients within one-year of ankle arthrodesis and in 6.2% (95% CI, 5.1-7.2) of patients within three-years. Obese patients increased odds of nonunion on multivariable analysis (OR 1.6 [95% CI, 1.3-2.0]; P<0.001). On multivariable analysis, diabetes (OR 1.7 [95% CI, 1.2-2.6]; P=0.010) and each one-unit increase in Elixhauser Comorbidity Index scores (OR 1.1 [95% CI, 1.1-1.2]; P<0.001) contributed to increased odds of infection after ankle arthrodesis. CONCLUSION: Nonunion and infection are common complications following ankle arthrodesis with a three-year probability of 16% and 6%, respectively. Over one-quarter of patients with nonunion post-ankle arthrodesis experience a delay in diagnosis past one- year. The risk of post-ankle arthrodesis nonunion is highest in patients with obesity; the risk of infection is highest in patients with diabetes or an elevated Elixhauser Comorbidity Index score. Although diabetes and its associated 'poor biology' is often viewed as the culprit in an obese diabetic who fails to heal, our research suggests that we should pay more attention to the mechanical and biologic consequences of obesity.