Instability severity index score values below 7 do not predict recurrence after arthroscopic Bankart repair

Purpose To evaluate the efficacy of the Instability Severity Index Score (ISIS) in predicting an increased recurrence risk after an arthroscopic Bankart repair. Methods Retrospective review of a cohort of patients operated in three different centres. The inclusion criteria (recurrent anterior instability [dislocation or subluxation] with or without hyperlaxity, arthroscopic Bankart repair) and the exclusion criteria (concomitant rotator cuff lesion, acute first-time dislocation, surgery after a previous anterior stabilization, surgery for an unstable shoulder without true dislocation or subluxation; multidirectional instability) were those used in the study that defined the ISIS score. The medical records and a telephone interview were used to identify the six variables that define the ISIS and identify recurrences. Results One hundred and sixty-three shoulders met the inclusion and exclusion criteria. Of these, 140 subjects (22 females/118 males; mean age 35.5 ± 7.9) with 142 (89.0%) shoulders were available for follow-up after 5.3 (1.1) (range 3.1–7.4) years. There were 20 recurrences (14.1%). The mean (SD) preoperative ISIS was 1.8 (1.6) in the patients without recurrence and 1.8 (1.9) in the patients with recurrence (n.s.). In the 117 subjects with ISIS between 0 and 3 the recurrence rate was 12.8%; in the 25 with ISIS 4 to 6 the rate was 20% (n.s.). Conclusion For subjects with anterior shoulder instability in which an arthroscopic Bankart repair is being considered, the use of the ISIS, when the values obtained are ≤ 6 was not useful to predict an increased recurrence risk in the midterm in this retrospectively evaluated case series. The efficacy of the ISIS score in defining a group of subjects with a preoperative increased risk of recurrence after an arthroscopic Bankart instability repair is limited in lower risk populations (with ISIS scores ≤ 6). Level of evidence Retrospective case series, Level IV.