The distance to dislocation outperforms the instability severity index score in predicting recurrent instability after arthroscopic Bankart repair in a military population.

Abstract

Although risk factors for recurrent instability following arthroscopic Bankart repair (ABR) have been extensively investigated in the general population, research focusing specifically on military cohorts remains scarce. This study aimed to assess the predictive value of the Instability Shoulder Index (ISI) score and distance to dislocation (DTD) for recurrent instability following ABR in a military population. We conducted a retrospective single-center cohort study of military personnel who underwent ABR between 2009 and 2022, with a minimum follow-up of 2 years. Recurrent instability was assessed as the primary outcome. Clinical and radiologic parameters were analyzed. Univariate and multivariate logistic regression analysis identified independent predictors of recurrence, and receiver operating characteristic (ROC) curves were used to quantify predictive performance. A subgroup analysis stratified by age was also performed. A total of 152 patients (147 male) with a mean age of 24.2 ± 4.9 years and a mean follow-up 88.8 ± 40.9 months were included. Recurrent instability occurred in 24 patients (15.8%). Patients with recurrence had comparable ISI score to those without (P = 0.078) but exhibited significantly and shorter DTD (P < 0.001). Multivariate logistic regression analysis identified DTD as an independent predictor of recurrence. The ROC curve showed that the area under the curve (AUC) for DTD was 0.754, with an optimal cutoff value of 5.3 mm. Additionally, the AUC for DTD in patients aged ≤ 20 years and > 20 years were 0.863 and 0.725, respectively. In military personnel, a shorter DTD was predictive of recurrent instability following ABR, and alternative stabilization procedures should be considered when DTD is ≤ 5.3 mm. Furthermore, ISI score had no association with recurrence; however, this analysis was underpowered.