3D-MRI FRACTURE Sequence is equivalent to 3D-CT in quantifying bone loss and measuring shoulder morphology in patients with shoulder dislocation.

PURPOSE: To evaluate the equivalence of 3D-MRI (Fast field echo Resembling A CT Using Restricted Echo-spacing,FRACTURE) and 3D-CT in quantifying bone loss in patients with shoulder dislocation and measuring morphological parameters of the shoulder.

METHODS: From July 2022 to June 2023,patients with anterior shoulder dislocation who were over 18 years of age and underwent both MRI and CT within 1 week were included in the study.The MRI protocol included an additional FRACTURE sequence.3D reconstructions of MRI(FRACTURE) and CT were completed by two independent observers using Mimics 21.0 software through simple threshold-based segmentation.For bone defect cases, two independent observers evaluated glenoid defect, percentage of glenoid defect,glenoid track(GT), Hill-Sachs Interval (HSI), and "on-track/off-track".For all cases,glenoid width, glenoid height,humeral head fitting sphere radius,Critical Shoulder Angle(CSA),glenoid version,vault depth, and post-processing time were assessed.Paired t-test was utilized to assess the difference between 3D-CT and 3D-MRI (FRACTURE).Bland-Altman plot was constructed to evaluate the consistency between 3D-CT and 3D-MRI (FRACTURE). Inter- and intra-observer agreement was evaluated by Interclass Correlation Coefficient (ICC). Paired chi-square test and Cohen's kappa statistic were used for binary variable("on-track/off-track").

RESULTS: A total of 56 patients(16 bipolar bone defect, 5 only Hill-Sachs lesion,35 without bone defect) were eventually enrolled in the study.The measurements of 21 bone defect cases showed no statistical difference between 3D-CT and 3D-MRI.Glenoid defect,3D-CT(4.05±1.44mm) vs 3D-MRI(4.16±1.39mm,P=0.208);Percentage of glenoid defect,3D-CT(16.21±5.95%) vs 3D-MRI(16.61±5.66%, P=0.199);Glenoid Track,3D-CT (18.02±2.97mm) vs 3D-MRI(18.08±2.98mm, P=0.659);Hill-Sachs Interval,3D-CT (14.29±1.93mm) vs 3D-MRI(14.35±2.07mm, P=0.668).No significant difference was found between 3D-CT and 3D-MRI in the diagnosis of "on-track/off-track"(P=1.000), and the diagnostic agreement was perfect (Kappa=1.00,P=0.000). There was no statistical difference between two examination methods in the measurements of all 56 cases,except that the post-processing time of 3D-MRI was obviously longer than that of 3D-CT.Glenoid height,3D-CT(34.56±1.98mm) vs 3D-MRI (34.67±2.01mm, P=0.139).Glenoid width,3D-CT(25.32±1.48mm) vs 3D-MRI(25.45±1.47mm, P=0.113).Humeral head fitting sphere radius,3D-CT(22.91±1.70mm) vs 3D-MRI(23.00±1.76mm, P=0.211).Critical Shoulder Angle,3D-CT(33.49°±2.55°) vs 3D-MRI (33.57°±2.51°, P=0.328). Glenoid version, 3D-CT(-3.25°±2.57°) vs 3D-MRI (-3.18°±2.57°, P=0.322).Vault depth,3D-CT(37.43±1.68mm) vs 3D-MRI(37.58±1.75mm, P=0.164).Post-processing time,3D-CT(89.66±10.20s) vs 3D-MRI (360.93±26.76s, P=0.000).For all assessments, the Bland-Altman plots demonstrated excellent consistency between two examination methods,and the ICCs revealed excellent inter-observer and intra-observer agreement.

CONCLUSIONS: 3D-MRI (FRACTURE) is equivalent to 3D-CT in quantifying bone loss in patients with shoulder dislocation and measuring shoulder morphological parameters.