Treatment of Thoracolumbar Burst Fractures With Flexion-Distraction Injury of The Posterior Elements

Purpose: Some of the spinal column injuries involve combined mechanisms that can be overlooked or missed and result in increased morbidity and mistakes in determining the proper method of treatment. Combined effect of flexion and axial loading may result in such an injury that vertebral body fracture occurs with flexion distraction injury of the posterior elements. The purpose of this study is to report on diagnostic and therapeutic aspects of thoracolumbar burst fractures associated with flexion-distraction injury of the posterior elements.

Materials and Method: 44 patients were treated between 1991-2000 for thoracolumbar burst fractures with flexion distraction injury of the posterior elements. Level of injury was L1 in 16, L2 in 14, T12 in 10, T11 in 2 and L3 in 2. Radiological evaluation was made by anteroposterior, lateral, bilateral oblique radiographs, computerized tomography (with high resolution frontal and sagittal reconstructions whenever possible) and magnetic resonance imaging. Preoperative kyphosis and sagittal index were 25.4º and 28.4º respectively. All patients had first posterior instrumentation, reduction and stabilization and then anterior decompression and fusion as a second procedure either same, sitting or staged. 11 patients had preoperative neurologic deficits (4 Frankel B, 7 Frankel D). All 11 patients had lamina fractures which was explored during surgery and 6 were noted to have traumatic dura lesions. Strut autograft (fibula or iliac crest) was used in 14 and titanium mesh cage in 30 for anterior fusion. Additionally 3 patients had Kaneda instrumentation and 11 patients had one screw above and one screw below anterior instrumentation. As posterior instrumentation hooks were used in 3 patients and pedicle screws were used in the remaining. As a surgical finding, posterior separation was ligamentous in 28 and osseous in 16 patients. Canal compromise was 62% on average on CT scans.Results : Average follow up was 46 (28-98) months. As for neurologic recovery, 3 Frankel B became Frankel D, 1 Frankel B became Frankel E. 4 Frankel D patients improved to E and 3 remains unchanged. Correction of kyphosis postoperatively averaged 98%. No correction loss, no implant failure and no pseudoarthrosis were noted during follow up.

Conclusion: The combined forces of flexion, compression and posterior distraction constitute the mechanism involved in the flexion-distraction injury associated with vertebral body fracture. Precise diagnosis of posterior ligamentous complex injury permits evaluation of the mechanical instability and differentiation of unstable and stable burst fractures. Isolated anterior approach may be inadequate in cases with sagittal index higher than 25 degrees and more than 50% loss of vertebral body height. Also it is unsuitable for patients with neurologic symptoms. The preferred surgical treatment should be initial posterior exploration, reduction and stabilization by instrumentation and then anterior approach as a second stage procedure to provide both decompression and mechanical support.