Comparison of conventional MRI and CT scans for assessing bony parameters and classifying On- and Off-Track lesions in anterior shoulder dislocations

Abstract

Background: Shoulder dislocation is the most common major joint dislocation, with anterior dislocations accounting for 95% of cases. Accurate assessment of bony lesions, such as glenoid bone loss (GBL) and Hill-Sachs lesions, is critical for treatment planning. While computed tomography (CT) is the gold standard for evaluating bony parameters, magnetic resonance imaging (MRI) may serve as a viable alternative, offering no radiation exposure. This study aims to compare the reliability of conventional 2D (two- Dimensional)-MRI with 2D-CT in measuring bony parameters and classifying lesions as on- or off-track. It was hypothesized that there is no difference in evaluation between MRI and conventional CT scans. Methods: A retrospective case-control study was conducted on 61 patients (mean age 45 ± 19 years) with anterior shoulder dislocations who underwent both CT and MRI imaging. Radiographic measurements, including glenoid diameter, glenoid defect (in width), Hill-Sachs lesion and bony bridge, were obtained independently from CT and MRI scans. Patients were categorized as on- or off-track based on the glenoid track and Hill-Sachs index. Statistical analyses included correlation tests, Bland-Altman plots, interrater agreement (intraclass correlation coefficient), and sensitivity and specificity analyses for lesion classification. Results: MRI showed good agreement with CT across most parameters, with mean differences of less than 1 mm for glenoid defect, glenoid diameter, and Hill-Sachs lesions. Correlation coefficients ranged from 0.62 (bony bridge) to 0.93 (glenoid defect). Bland-Altman plots revealed good agreement for glenoid parameters but higher variance for the Hill-Sachs lesion and bony bridge. MRI correctly classified 89% of on-track lesions (sensitivity) and 76% of off-track lesions (specificity). Interrater agreement was excellent for glenoid defect measurements (ICC = 0.962) and lower for the bony bridge (ICC = 0.848). Conclusion: Conventional MRI demonstrates high reliability in measuring bony parameters and good accuracy in classifying on- and off-track lesions compared to CT. MRI is a viable alternative for preoperative evaluation, particularly in cases with minor bony defects. However, in indeterminate defects, a CT scan is recommended to ensure accurate measurements, classification and treatment planning. Level of evidence: Level III.