Using the "Hill-Sachs interval to glenoid track width ratio" for prediction of recurrent instability after arthroscopic Bankart repair.

INTRODUCTION: The glenoid track concept was used to confirm the engaging Hill-Sachs lesion (HSL) as a risk factor for recurrent instability following arthroscopic Bankart repair (ABR). However, the post-operative condition of soft tissue in vivo was not comparable to that designed in the intact condition in vitro in the original study of the glenoid track concept. Herein, the possibility of engagement may be underestimated.

HYPOTHESIS: A threshold of the Hill-Sachs interval to glenoid track width ratio (H/G ratio) that is related to recurrent instability after ABR could be found, in order to adjust the original glenoid track concept.

PATIENTS AND METHODS: Patients who underwent ABR with minimum 24-months follow-up were reviewed retrospectively. The primary outcome was evaluated with the recurrent instability. The H/G ratio of individual patients was used to calculate the sensitivity, specificity, and a receiver operating characteristic (ROC) curve, which aimed to establish a H/G ratio threshold related to recurrent instability after ABR.

RESULTS: From June 2005 to December 2013, 160 patients with a mean age of 27.7years were enrolled. The mean follow-up period was 77.2 months. The ROC curve indicated that H/G ratio≥0.7 had the sensitivity and specificity of 0.74 and 0.71, respectively, in predicting recurrent instability. On univariate logistic regression analysis, the H/G ratio≥0.7 was a significant predictor of higher risk for recurrent instability (p<0.001).

DISCUSSION: H/G ratio seems to be a reliable parameter for predicting recurrent instability. H/G ratio≥0.7 may be considered as a positive predictor for recurrent instability after ABR.

LEVEL OF EVIDENCE: Level IV: retrospective diagnostic study.