Summary

In this case-control study assessing CT-based glenoid concavity and version, concavity is a relevant factor for osteochondral, anterior shoulder stability, while glenoid version shows only limited influence.

Abstract

Background

The importance of glenoid concavity and version has been highlighted in several, recent studies. Biomechanically, glenoid concavity was shown to correlate highly with anterior shoulder stability. Loss of concavity as well as reduced glenoid retroversion is associated with a biomechanical loss of anterior stability. With this study, we aimed at assessing the clinical relevance of concavity and version as stabilizing factors. We hypothesized that low glenoid concavity and low retroversion are associated with anterior glenohumeral instability.

Methods

This single-center, retrospective case-control study was performed at our level-I-trauma center. CT scans of n=34 patients suffering from acute, isolated, and first-time anteroinferior glenohumeral dislocation between 2015 and 2021 were included. Patients with glenoid fractures, preexisting glenohumeral pathologies and incomplete CT imaging were excluded. In the control group, n=68 polytrauma patients referred to our hospital were included, who neither showed acute nor chronic glenohumeral pathologies. Both groups were matched age- and gender-specifically in a 2:1 ratio.
Glenoid radius, depth, and concavity according to the bony shoulder stability ratio (BSSR) were measured in both, anterior-posterior (a.p.) and superior-inferior (s.i.) direction. Version was measured by the glenoid vault method.

Results

The instability cohort presented with a lower BSSR(s.i.) compared to the control group (49.8% vs. 56.9%, p=0.001). The BSSR(a.p.) did not differ significantly (30.2% vs. 33.7%, p=0.163). A higher retroversion was seen in the instability cohort (-13.1° vs. -11.4°; p=0.041). Subgroup analyses showed higher BSSR(s.i./a.p.) in ≥60-year-old patients compared to ≤30-year-old patients (for BSSR(s.i.) 61.4% vs. 50.4%; p=0.0002; for BSSR(a.p.) 37.5% vs. 27.3%; p=0.0081). Glenoid version did neither differ age- nor gender-specifically.

Conclusion

Glenoid concavity is a relevant factor for anterior shoulder stability, not only in biomechanical studies, but also in the clinical setting. In contrast to recent biomechanical studies, glenoid version appears to have only limited clinical impact on anterior stability in this study. Regarding the individual treatment of anterior glenohumeral instability, glenoid concavity should be focussed on as an important osteochondral stabilizing factor.