Burden And Rehabilitation Care Of Chronic Ankle Instability In Military Tactical Athletes. A Retrospective Population Study.

Abstract

PURPOSE: To assess estimated population-level burden of Chronic Ankle Instability (CAI) and rehabilitation care patterns in the US military health system from 2000 to 2019. METHODS: The Military Health System Data Repository was used to identify cases with an outpatient diagnosis of lateral ankle sprain (LAS) and associated rehabilitation care in all active-duty service members from 2000 to 2019. Individuals with one care episode were classified as index LAS; two care episodes separated by ≥365 days as “possible CAI;” and cases with ≥3 care episodes (>365 days from index) as CAI. Multinomial logistic regression assessed the effects of sex, time in service, service branch, age at index sprain, and number of deployments on the diagnostic classification. RESULTS: A total of 422,978 military tactical athletes sought care for LAS during the study epoch (22,262 cases annually), with 81.8% of the cases (n = 346,119) classified as having an index LAS, 12.8% (n = 54,133) as possible CAI, and 5.4%, (n = 22,726) as CAI. When pooled, the cases classified as either possible CAI or CAI comprised 18.2% of all lateral ankle injuries (n = 76,859). Several significant factors were associated with injury chronification: female sex (OR: 1.05 to 1.25), age < 30 years (OR: 2.13 to 3.30), >7 years of service (OR: 2.17 to 5.38), and ≥ 2 deployments (OR 1.13 to 1.20). There were no other significant associations. Only 12.3% of individuals with LAS, 24.9% with possible CAI, and 59.0% with CAI were evaluated by a rehabilitation specialist. Rehabilitation care consisted primarily of therapeutic or aquatic exercises (3.5 to 5.1 units/episode), thermal modalities (1.8 to 2.2 units/episode), and functional/sensorimotor re-education interventions (1.6 to 2.2 units per episode). Of those provided rehabilitation care, 71% of index LAS, 68% of possible CAI, and 90% of the CAI group received care beyond 30 days. CONCLUSION: There was a substantial burden of LAS and CAI observed in military tactical athletes, with several salient factors associated with injury chronification. Only a small proportion were provided rehabilitation care. To our knowledge, this is the first study to estimate the epidemiological burden of CAI in the military population.