Increased Glenoid Index is a Risk Factor for Pediatric Anterior Glenohumeral Dislocation: An MRI-Based Case-Control Study

OBJECTIVES: In the adult population, anterior glenohumeral instability has been associated with a tall and narrow glenoid morphology, assessed using glenoid index (GI). This morphological association has not been assessed in children and adolescents. This study was designed to examine the association of GI with anterior glenohumeral dislocation in patients 19 years old and younger using a case-control study design. METHODS: An institutional radiology database was queried over a 10-year period to identify patients 19 years old and younger who underwent glenohumeral MRI arthrography and were diagnosed with anterior shoulder dislocation (cases) and those without dislocation and normal shoulder arthrogram studies (controls). Those with bony Bankart lesions were excluded. Glenoid index (glenoid height-to-width ratio) was measured by an attending pediatric musculoskeletal radiologist and a fellowship-trained attending orthopedic surgeon. Comparative analysis between the two groups was performed using Student’s t-test for each variable, followed by receiver-operating-characteristic (ROC) analysis to determine discriminative ability when statistically significant. RESULTS: Thirty-three males and 22 females (mean age: 15.4±2.1 years old) meeting inclusion and exclusion criteria were identified. Mean glenoid index in the dislocator group was significantly greater than the control group (1.55±0.14 vs. 1.38±0.08, P<0.001). ROC analysis revealed adequate discrimination of glenoid index in predicting glenohumeral dislocation (area under the curve [AUC] = 0.88). A glenoid index ≥1.45 was 83% sensitive and 79% specific for predicting dislocation in the study cohort. CONCLUSION: Patients with anterior glenohumeral dislocation were noted to have increased glenoid index (taller and narrower glenoid morphology) than controls. Glenoid index may help identify patients at risk for primary or recurrent anterior glenohumeral instability events, and can help guide treatment and anticipatory guidance.