Study design: This is a report of a patient with a rare unstable 3-column ligamentous injury of the thoracic spine.
Objective: To illustrate a rare unstable thoracic spine injury that required internal fixation despite its potentially benign clinical and radiologic presentation.
Summary of background data: Extension injury of the thoracolumbar spine is uncommon. Although there have been several reports of hyperextension injuries in the thoracolumbar spine, the radiologic findings of the present case was different from those in the previously reported cases.
Methods: The clinical findings, roentgenographic appearance, treatment, were presented and the mechanism of this lesion was analyzed.
Results: Physical examination revealed mild weakness in his left hip flexor and quadriceps, ASIA-D motor score of 96. There was no tenderness or step deformity on assessment of his back. The initial roentgenograms showed no evidence of fracture or malalignment. However, evaluation of his computed tomography scan axial images showed a lateral superior endplate fracture, small fracture fragment from T11 right inferior articular process, widening of the left facet joint, and deformed T11 spinous process. The computed tomography scan sagittal images showed a vertical fracture fragment in the central spinal canal. The fragment may have arisen from the posterior cortex of the vertebral body, possibly due to elevation of the PLL. Magnetic resonance imaging (MRI) was obtained due to the suspicion that a much more severe underlying injury was present. The MRI demonstrated disc disruption and high intensity signals in the region of ALL, PLL, ligamentum flavum, supraspinous, and interspinous ligaments as well as in the spinal cord at T11-T12. The MRI also showed high intensity signals in the facet joints at T11-T12. Intraoperative assessment confirmed disruption of the supraspinous and interspinous ligaments, facet capsules and the ligamentum flavum, which was avulsed from its insertion on the underside of the T11 lamina on both sides. There was a tendency during the procedure of the spine to hyperextend, and "fish mouth" at the T11-T12 level, which confirmed the likelihood of this being an extension mechanism. The patient was treated with single segment posterior spine decompression, instrumentation, and fusion.
Conclusion: A high index of suspicion is necessary to identify such extremely unstable injury despite its relative benign clinical and radiologic presentation.