Glenoid index: a new risk factor for recurrence of glenohumeral instability after arthroscopic Bankart repair

BACKGROUND: The glenoid index (GI) (glenoid height to width ratio) has been shown to be a risk factor for instability in young healthy athletes. Nevertheless, whether the altered GI is a risk factor for recurrence after a Bankart repair remains unknown. METHODS: Between 2014 and 2018, 148 patients ≥ 18 years old with anterior glenohumeral instability underwent a primary arthroscopic Bankart repair in our institution. We assessed return to sports, functional outcomes, and complications. We evaluate the association between the altered GI and the probabilities of recurrence in the postoperative period. Intraclass correlation coefficient was used to determine interobserver reliability. RESULTS: The mean age at the time of surgery was 25.6 years old (19 to 29), and the mean follow-up was 53.3 months (29 to 89). The 95 shoulders who met the inclusion criteria were divided into 2 cohorts, 47 shoulders had a GI ≤ 1.58 (group A) and 48 had a GI > 1.58 (group B). At the final follow-up, 5 shoulders in group A (10.6%) and 17 shoulders in group B (35.4%) suffered a recurrence of instability. Those patients with a GI > 1.58 had a hazard ratio of 3.86 (95% confidence interval: 1.42-10.48) (P = .004) compared with those with a GI ≤ 1.58 of suffering a recurrence. When correlating GI measurements between raters, we observed an intraclass correlation coefficient of 0.76 (95% confidence interval: 0.63-0.84), these results fall under the qualitative definition of good interobserver agreement. CONCLUSION: In young active patients with an arthroscopic Bankart repair, an increased GI was associated with a significantly higher rate of postoperative recurrences. Specifically, those subjects with a GI > 1.58 had 3.86 times the risk of recurrence than those subjects with a GI ≤ 1.58.