Histological And MRI Evaluation Of Intervertebral Disc Injury In Type A Thoracolumbar Fracture

Objective: To observe histological change of intervertebral disc in fresh and old thoracolumbar fractures and the diagnosing accuracy of magnetic resonance image (MRI) for intervertebral disc injury. Methods: From 2006 to 2010, 25 patients with type A thoracolumbar fracture, including 15 of fresh fractures (fracture within 3 weeks) and 10 of old fractures (fracture beyond 3 weeks) were included into the analysis. All factures were managed with anterior approach after detailed evaluation using roentgenography, computed tomography (CT) and magnetic resonance MRI. The superior and inferior intervertebral discs adjacent to the injured vertebral body were removed and extracted for histological analysis. The accuracy of magnetic resonance image in defining disc injury was evaluated according to the histological findings after operation. Results: In fresh fracture,the superior intervertebral height decreased in 9 patients and the inferior intervertebral height in 3 patients on plain films respectively. the discs herniated into the vertebral body in 5 patients. CT scan showed the decreased upper and lower intervertebral height in 10 and 4 patients respectively and the herniation of the disc into vertebral body was found in 6 patients. The decreased upper and lower intervertebral height was found in 10 and 4 patients on MRI respectively and the herniation of the disc into vertebral body was found in 6 patients. The signal change of the upper intervertebral discs was found in 12 patients. HE stains revealed annulus ruptures, structural disorder and matrix density increase in 16 discs. In old fracture, plain films showed the decrease of the superior and inferior intervertebral height in 7 and 4 patients respectively.The discs in 6 patients were found herniated into the vertebral body and the superior and inferior intervertebral height decreased in 7 and 4 patients respectively on CT scan. The herniation of the disc into vertebral body was found in 5 patients. MRI showed decreased superior and inferior intervertebral height in 7 and 4 patients respectively and the herniation of the disc into vertebral body was defined in 5 patients. The signal change of the r intervertebral discs was found in 7 patients. In HE stains, hypertrophy of capillaries within discs, replacement of disc with fibrous scar and decrease of chondroid cells (or replaced by fibroblast) were found in 11 discs, including 7 of superior and 4 of inferior intervertebral discs. Conclusion: The injured disc in type A thoracolumbar fractures is healed and replaced with fibrous tissues, losing its normal structural and functional integrities. MRI is reliable in diagnosis of injured intervertebral disc and the manifestation in MRI has 6 different patterns. The presence of injured disc in type A thoracolumbar fractures can be an indication for surgical intervention and intervertebral fusion procedure.