A comparative analysis of glenoid morphology in on-track and off-track lesions following anterior shoulder dislocation

Background: Anterior shoulder dislocation is a prevalent clinical issue, with high recurrence rates after initial dislocation. Stability of the shoulder joint is maintained by the interplay of static and dynamic stabilizers, including the glenoid and humeral head morphology. Glenoid morphology has been identified as particularly influential in joint stability, and thus the evaluation of glenoid bone loss is crucial in managing shoulder dislocations. This study aimed to investigate the differences in glenoid morphologies between on-track and off-track lesions postdislocation. Methods: This retrospective case-control study included patients who presented with shoulder dislocation at a level 1 trauma center from 2011 to 2020. Patients with anterior shoulder dislocation, complete computed tomography imaging, visible bone loss, and those aged 18 years or more were included. Radiographic parameters were assessed using a certified picture achieving and communication system workstation. The groups were divided into on-track or off-track lesions and their glenoid version, glenoid concavity, and the morphometrical-based bony shoulder stability ratio (BSSR) were compared. Results: Two hundred twelve patients (70% male and mean age of 50 years) were included and no significant difference was found between the on-track and off-track groups in terms of demographics or injury mechanism. Significant differences were noted in the glenoid defect (1.28 mm vs. 4.67 mm, P = .001), glenoid concavity/depth (1.7 mm vs. 1.3 mm, P = .001), the BSSR (40% vs. 33%, P = .001), and glenoid retroversion (4.4 vs. 2.9°, P = .009). Conclusion: Glenoid morphology has become an increasing focus in the treatment of anterior shoulder dislocation. Patients with an off-track lesion appear to have not only greater glenoid loss and a larger Hill-Sachs but also a flatter glenoid with less retroversion. This also appears to lead to a lower BSSR.