Increased Glenoid Index as a Risk Factor for Pediatric and Adolescent Anterior Glenohumeral Dislocation: An MRI-Based, Case-Control Study

BACKGROUND: In adults, anterior glenohumeral instability has been associated with a tall and narrow glenoid morphology, assessed using the glenoid index (GI; glenoid height-to-width ratio) on magnetic resonance imaging (MRI). This morphological association has not been assessed in children and adolescents. PURPOSE/HYPOTHESIS: To examine the association of GI and other MRI measurements of interest supported in studies on adults with anterior glenohumeral dislocation in patients aged ≤19 years. We hypothesized that these patients would have a significantly greater GI (relatively taller and narrower glenoid morphology) compared with healthy controls. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: An institutional radiology database was queried over a 10-year period to identify patients aged ≤19 years who had been diagnosed with radiographically confirmed anterior shoulder dislocation and who underwent glenohumeral magnetic resonance arthrography as well as those without dislocation with normal shoulder arthrogram studies (controls). Patients with bony Bankart lesions were excluded. The following glenohumeral dimensions were measured on shoulder arthrogram: GI, glenoid version, coracohumeral interval, and rotator interval width/depth. Comparative analysis between the 2 groups was performed using the Student t test for each variable, followed by receiver operating characteristic (ROC) analysis to determine discriminative ability when statistically significant. RESULTS: Overall, 55 participants (33 male and 22 female patients; mean age, 15.4 ± 2.1 years) were enrolled; 22 patients were in included in the dislocator group and 33 patients comprised the control group. The mean GI in the dislocator group was significantly greater than the control group (1.55 ± 0.14 vs. 1.38 ± 0.08; P < .001). ROC analysis revealed adequate discrimination of GI in predicting glenohumeral dislocation (area under the curve = 0.88). A GI ≥1.45 was 83% sensitive and 79% specific for predicting dislocation in the study cohort. CONCLUSION: Patients with anterior glenohumeral dislocation had increased GI (taller and narrower glenoid morphology) than controls. This useful MRI measurement may help identify patients at risk for primary or recurrent anterior glenohumeral instability events and may therefore help with guiding treatment and prevention.