Increased Calcaneal Pitch and Subtalar Instability are Predictors Associated with Surgical Reconstruction for Patients who Develop Chronic Lateral Ankle Instability

Abstract

Category: Ankle; Sports Introduction/Purpose: Most acute lateral ankle sprains are treated non-operatively, however, up to 20% of acute sprains (LAS) develop Chronic Lateral Ankle Instability (CLAI) requiring surgical reconstruction. CLAI risk factors have not been analyzed in the context of a multifactorial system. This study aims to identify a model to identify patients who are at increased risk for CLAI after acute lateral ankle sprains utilizing clinical and radiographic findings, in order to identify patients who may benefit from early surgical intervention (LAR). Methods: This retrospective study identified 78 patients who presented with acute lateral ankle sprains and 50 patients with CLAI who underwent lateral ankle reconstruction (LAR), diagnosed 2010-2020. Patients’ clinical exam findings and radiographic data were collected from direct clinical notes evaluation from a single Orthopedic Foot and Ankle surgeon's records. Descriptive statistics were utilized to determine difference, with a regression model used to determine risk factor significance. Results: A clinical diagnosis of subtalar instability (SI) was made in 32% of CLAI patients as compared to 2.5% (p=0.0001) of acute sprains. Assessment of calcaneal pitch (CP) yielded a significant difference between CLAI [µ:30.7, Median: 30.9] and acute sprains [µ=25.8, p< 0.0001, Median=25.8]. Correlation analysis yielded a predictive model for CLAI; -10.618 + 0.328CP + 3.33SI, indicating both increased calcaneal pitch [OR: 1.388 (95% CI: 1.185-1.625)] and subtalar instability [OR: 27.931 (95% CI: 4.235 – 184.210)] are significant predictors of CLAI. The sensitivity of this model is 62.5% and specificity is 83.3%, with both variables demonstrating a significance (P < 0.001 for both variables). Conclusion: These data indicate subtalar instability and increased calcaneal pitch angle are predictors of CLAI development and a higher risk of requiring LAR after LAS. These predictors can aid clinicians in determining ideal candidates for more aggressive non- operative treatment and those who may necessitate earlier surgical lateral ankle reconstruction. Identification of these patients will assist the clinician in management, counseling, treatment, and evaluation after LAS and after developing more chronic symptoms. Future prospective studies are needed to further characterize these risk factors as indicators for failure of and optimal non- operative management as well as patients who may qualify for early LAR.