Preoperative Instability Episodes as a Predictor of Recurrence After Arthroscopic Bankart Repair

Background: Previous literature has demonstrated that an increased number of preoperative anterior shoulder instability episodes is associated with recurrent anterior shoulder instability after arthroscopic Bankart repair (ABR). However, a threshold for the number of preoperative instability episodes that increases the risk of recurrent anterior shoulder instability is not well established. Purpose: To establish a threshold value for the number of preoperative instability episodes that predicts recurrent anterior shoulder instability after ABR and to compare glenoid bone loss, the Hill-Sachs interval, and the distance to dislocation between patients who have surpassed the threshold and those who have not. Study Design: Retrospective cohort study; Level of evidence, 3. Methods: This retrospective review included consecutive patients with “on-track” Hill-Sachs lesions who underwent primary ABR for anterior shoulder instability at a single institution between 2007 and 2019. Patients with an unknown number of preoperative instability episodes, >20% glenoid bone loss, <2 years’ follow-up, or age >40 or <14 years were excluded. Logistic regression assessed associations between preoperative anterior shoulder instability episodes and recurrent anterior shoulder instability after ABR, defined as a recurrent subluxation or dislocation. Receiver operating characteristic analysis determined the optimal threshold of preoperative anterior shoulder instability episodes to predict recurrent anterior shoulder instability. Significance was set as P < .050. Results: A total of 151 patients (mean age, 20 ± 5 years; mean follow-up, 6.0 ± 3.1 years) were included, of whom 28 (19%) experienced recurrent anterior shoulder instability. Multiple thresholds showed increased odds of recurrent anterior shoulder instability: ≥2 preoperative anterior shoulder instability events (odds ratio [OR], 9.70 [95% CI, 2.63-35.70]; P = .001), ≥3 events (OR, 3.47 [95% CI, 1.37-8.80]; P = .009), and ≥4 events (OR, 3.08 [95% CI, 1.17-8.08]; P = .023). Receiver operating characteristic analysis revealed that ≥2 preoperative anterior shoulder instability events was the strongest predictor of recurrent anterior shoulder instability (area under the curve = 0.72). Conclusion: A threshold of ≥2 preoperative anterior shoulder instability episodes best predicted recurrent anterior shoulder instability after ABR. Stratification beyond 1 versus ≥2 preoperative anterior shoulder instability episodes did not increase predictive ability. This finding may help surgeons to counsel patients and consider earlier surgical stabilization in those who have sustained anterior shoulder instability episodes.