Objective To evaluate MRI appearancs and its diagnostic value on sacral insufficiency fractures.Methods Sacralinsufficiency fractures in 21 patients(19 females and 2 males,mean age 72.4 years old) with osteoporosis(n=21) and post-radiation for pelvis malignant tumors(n=7) were performed MRI examination with sagittal,axial,and coronal SE T_1WI,FSE T_2WI,and Fat-Sat FSE T_2WI,respectively.Contrast-enhanced SE T_1WI were performed in 14 patients.X-ray plain film(n=21),CT scans(n=21),and bone scans(n=14) were used to confirm each diagnosis of the fractures.Results Thirty-seven fractures of the patients were involved in the sacral alae in 16 cases(76.2%) with bilateral and 5 cases(23.8%) with unilateral.The fracture lines were demonstrated as low signalintensity on all of the sequences in 32 of 37 fractures(86.5%).The edema areas around the fracture lines were long T_1 and long T_2abnormal signal intensity in all of the fractures.The fracture lines and edema areas in 14 patients with contrast-enhancedscans demonstrated without enhancement and with inhomogeneous enhancement respectively.Three of 21 patients had multiple insufficiency fractures in other bones.Conclusion MRI is sensitive and specific in diagnosis of sacral insufficiency fracture.

Objective To study the pathogenesis of acute spinal epidural hematomas (ASEHs), MRI features, and its value on diagnosis and differential diagnosis. Methods Fifteen patients with ASEHs (8 males, 7 females, mean age 37.8 years) were reviewed. Seven of the patients were secondary to spinal injuries(5 spinal trauma, 1 post-spinal operation, and 1 post-lumbar puncture)and 8 were spontaneous. Eleven patients were confirmed by operation. MRI was performed in all patients in sagittal SE T 1WI and SE or FSE T 2WI, 12 in axial FSE T 2WI, 8 in axial SE T 1WI, and 4 in contrast-enhanced SE T 1WI. Results Fifteen ASEHs involved 18 spinal segments, 6 of the segments (6/18) in cervical spine, 9 segments (9/18) in thoracic spine, and 3 segments (3/18) in lumbar spine. The hematomas located at pre-epidural space in 7 segments (7/18) and at posterolateral epidural space in 11 segments (11/18). The craniocaudal extent of the hematomas varied from 1 to 13 vertebral levels (average 4.87 vertebral level). There were low signal intensity lines between hematomas and spinal cord in all of the cases on T 1WI. The low signal intensity line between hematoma and subarachnoid space was demonstrated in 8 cases (8/12) and 4 cases (4/15) on axial T 2WI and sagittal T 2WI, respectively. The figure of hematomas was biconvex on axial imaging in all of the cases, and long lentiform on sagittal imaging in 13 cases (13/15). The hematomas showed variable signal intensity. On T 1WI, 5 showed isointensity to cord, 6 with hyperintensity, and 4 with inhomogeneous iso-hyperintensity. On T 2WI, 5 showed hypointensity, 10 with inhomogeneous hypo-hyperintensity. There was no special MR manifestation after contrast administration. Conclusion ASEHs is a rare disorder, and MRI features are characteristic for the diagnosis and differential diagnosis.