Reliability of the Instability Severity Index Score as a Predictor of Recurrence after Arthroscopic Anterior Capsulolabral Reconstruction: A Multicenter Retrospective Study

BACKGROUND: Although the instability severity index score (ISIS) is widely used to predict recurrence after arthroscopic anterior instability surgery, its reliability, especially on the weightings and cutoff values, is questionable. The goal of the current retrospective study was to investigate recurrence after arthroscopic capsulolabral reconstruction to evaluate whether each domain of the ISIS has the appropriate predictive power for recurrence by using logistic regression analyses with odds ratios (ORs). METHODS: This study included 120 consecutive patients who underwent arthroscopic capsulolabral reconstruction between 2004 and 2016. We retrospectively reviewed patients' preoperative history and radiographs, postoperative recurrence or sensation of instability, and risk factors related to the ISIS. The mean postoperative follow-up was 27.6 months (range, 12 to 96 months; median, 21 months). Twenty-six patients with recurrence or positive apprehension were classified as the recurrence group; 94 patients without any symptoms were classified as the non-recurrence group. Logistic regression analyses with ORs were used to verify the utility of each domain of the ISIS for predicting recurrence. RESULTS: The mean ISIS did not differ significantly between the recurrence and non-recurrence groups (4.3 ± 1.8 vs. 3.4 ± 2.1 points; p = 0.063). Among the domains of ISIS, factors related to bone defects, the presence of a Hill-Sachs lesion and glenoid bone loss had the lowest ORs (0.77 and 0.38, respectively). CONCLUSIONS: Not all ISIS domains accurately predicted recurrence after arthroscopic capsulolabral reconstruction. The ISIS may not be a proper reference for determining Latarjet procedure in patients with anterior shoulder instability.