The Diagnostic Value Of Magnetic Resonance Imaging In Rib Micro-fractures

Objective To explore the magnetic resonance imaging(MRI)manifestations of rib micro-fractures and determine the utility of MRI through a comparative study of MRI and computed tomography(CT).Methods Twenty-five patients with mild chest trauma admitted to Nanjing Hospital Affiliated to Nanjing Medical University from February 2019 to December 2020 were recruited.All of the 25 patients underwent CT rescanning and 91 rib fractures of whom were confirmed by CT rescanning.The patients were subjected to CT and MRI within three weeks after the trauma,CT rescanning was scheduled 4–8 weeks later to classify rib fractures and determine the diagnostic accuracy and sensitivity of MRI and CT for rib micro-fractures.Fisher’s exact probability method was used to test the difference between MRI and first CT.Results The rib micro-fractures were divided into two types.Type I rib fractures showed complete or incomplete cortical fracture with extraosseous and/or intraosseous callus formation,whereas type II had an intact cortical bone with intraosseous callus formation.Type I fracture showed bone marrow edema with subperiosteal effusion in MRI,whereas type II showed bone marrow edema without subperiosteal effusion.Ninety-one rib fractures were confirmed by CT rescanning,of which 86(94.51%)were type I fractures and 5(5.49%)were type II.MRI identified90 fractures,of which 3 were false positive,with the diagnostic accuracy rate of92.55% and sensitivity rate of 95.60%.Among them,type I fractures(n = 85,3 were false positive)showed the MRI “sandwich” sign(heterogeneous high-signal shadow within bone marrow of the inner layer,low-signal bony cortex of the middle layer,and high-signal subperiosteal effusion of the outer layer)in both STIR and T2-SPAIR sequences;type II fractures(n = 5)displayed intramedullar high-signal intensities and no subperiosteal effusion.Fifty-five fractures(all type I)were discovered in the initial CT examination,and corresponding diagnostic accuracy rate and sensitivity rate were60.44%,which were lower than that of MRI.There was significant difference in the number of fractures detected by MRI and initial CT(P=0.027).Conclusion MRI has high sensitivity and accuracy in the diagnosis of rib micro-fractures,so it can be used as a routine supplementary examination besides CT for patients with mild chest trauma.