Summary

An inferiorly-based Hill-Sachs lesion represents a higher risk lesion as compared to superiorly-based lesions for recurrent instability following Bankart repair.

Abstract

Background

The on-track/off-track concept for shoulder instability primarily describes the medial-lateral rotational relationship between an engaging Hill-Sachs lesion and a Bankart defect. Though clinically more protective, on-track lesions retain some risk for failure following primary arthroscopic Bankart repair. While some of this risk can be explained by the “near-track” concept, the role of the superior-inferior position of the Hill-Sachs lesion has never been studied in the context of failure of primary Bankart repair. This study aims to identify the relationship between the superior-inferior position of a Hill-Sachs lesion and risk for failure following primary arthroscopic bankart repair. Our hypothesis is that inferiorly-based Hill-Sachs lesions may engage with the arm in neutral and thus be higher risk for failure following primary Bankart repair.

Methods

We performed a retrospective analysis of 201 individuals with on track lesions who underwent primary arthroscopic Bankart repair between 2007 and 2019 who have minimum 2 year follow-up. Patients with failure were defined as those who sustained a dislocation or subluxation after the index procedure. A pre-operative sagittal MRI cut showing the maximum Hill-Sachs diameter was used for position analysis. Sagittal position of the Hill-Sachs was defined the angle formed by the Hill-Sachs bisecting line through the humeral head center, against the mid-humeral axis on a sagittal MRI cut; An angle of 0 is twelve o’clock on the humeral head, while an angle of 90 is equatorial. We defined a priori four Hill-Sachs quadrants for semi-quantitative analysis, based on physiologic arm positions: Superior (angle < 40), Mid-Superior (40-60), Mid (61-90), and Inferior (>90). Hill-Sachs quadrants were then correlated against failure following primary arthroscopic Bankart repair.

Results

Failure rates following arthroscopic bankart repair as it relates to superior-inferior position of the Hill-Sachs lesion is as follows: No Hill-Sachs (10 of 73, 13.7%), Superior (0 of 7, 0%), mid-superior (6 of 36, 16.7%), Mid (19 of 71, 26.8%), and Inferior (1 of 6, 16.7%). We grouped Hill-Sachs lesions into low grade (No Hill-Sachs, Superior, and Mid-Superior quadrants) and high grade (Mid, and Inferior quadrants). Low grade represented a 13.8% risk of failure, while High grade represented a 26% risk for failure (p=0.034). Receiver Operating Characteristic (ROC) analysis demonstrates a Youden Index of 66 degrees as optimal cut-off for high-risk Hill-Sachs.

Conclusion

The superior-inferior sagittal position of a Hill-Sachs lesion may contribute to risk for failure of primary arthroscopic Bankart repair for on-track lesions. Inferiorly-based Hill-Sachs lesions may risk engagement at lower degrees of arm abduction, and in our study represent nearly double the risk of failure of arthroscopic Bankart repair as compared to superior Hill-Sachs positions.