Association Between Anterior Glenohumeral Instability and Glenoid Anteversion/inclination:An MRI-based study at the Agha Khan University and Kenyatta National Hospitals

Abstract

Background: The shoulder joint complex is made up of several articulations. The main articulation is the glenohumeral joint which works in concert with the acromioclavicular (ACJ), sternoclavicular (SCJ) and the scapulothoracic joints. The glenohumeral articulation has the most mobility in the body and is anatomically classified as a diarthrodial, multiaxial joint (1). The joint stabilizers, both dynamic and static allow for significant mobility of the joint in different planes predisposing the joint to instability and dislocations. Studies have shed more light on the pathological components having a bearing on shoulder instability among them bony and soft tissue contributions, and patient factors. The contribution of glenoid morphology to glenohumeral stability and the biomechanical factors that lead to humeral head impaction has been the subject of research (2). Multiple studies have shown increased glenoid retroversion as a contributor to posterior shoulder instability (2)(3)(4) but few studies report glenoid architecture as a contributing factor to anterior glenohumeral instability, despite it being the most common form of instability in the glenohumeral joint. Study objective: This study sought to find out the correlation between anterior glenohumeral instability and glenoid anteversion/inclination Study design: A retrospective, case-control study was carried out. Study setting: The study was carried out at the departments of radiology and imaging at Agha Khan University (AKUH) and Kenyatta National Hospitals (KNH). Methodology: Shoulder Magnetic Resonance Imaging (MRI) scans for patients between 18 to 45 years with anterior shoulder instability were used in the study and compared against a control consisting of shoulder MRIs of patients with other shoulder pathologies but having no incidences of dislocation e.g.., frozen shoulder, chronic shoulder pain. A structured data collection tool was used to collect the data Data processing: Data was analysed with Statistical Package for the Social Sciences (SPSS) version 26 and presented in summary as percentages and frequencies for categorical data, and as median with interquartile range or means with standard deviation for continuous data. Results: The mean age for the participants was 32.0 (SD 9.0) years. The mean age for the cases was 29.0 (SD 8.7) years, while for the controls was 34.6 (SD 8.5) years. The glenoid was anteverted in 40% and 35.6% of cases and controls respectively (p = 1.00) and retroverted in 60% and 64.4% of cases and controls respectively (p =0.666). Most of the glenoids were superiorly inclined (91.1% and 93.3% for cases and controls respectively. The mean glenoid version was 1.04 o retroversion (range -9.7 o to 16.3 o) or for the cases and 2.26 o retroversion (range -8.5 o to 21.5 o) for the controls. The mean inclination on the other hand was 10.51 o Superior (range -4.6 o to 29.7 o) for the cases and 10.80 o (range -2.6 o to 29.3 o) for the controls. The differences in the glenoid version and inclination between the cases and controls were not statistically significant (p = 0.288 and p = 0.489 for glenoid version and inclination respectively). Conclusion: Glenoid alignment doesn’t seem to be a risk factor for anterior glenohumeral instability.