Combined Burst Fracture and Flexion-Distraction Injury of the Thoracolumbar Spine - Analysis of the Injury Mechanism and Results of Surgical Treatment

• (d - DePuy Japan)

Purpose: This report is to analyze the injury mechanism of unstable three column injuries of combined burst fracture and flexion-distraction injury of the thoracolumbar spine and to evaluate clinical outcomes of the reconstructive surgeries.

Materials: Between January 1990 and December 1999, consecutive 39 patients (29 males,10 females) with the above injuries had been treated surgically. Their average age at surgery was 40 year-old from 16 to 73. Causes of injuries were fall from height in 20 patients, downfall from the edge of road driving with a seat belt in 15 and heavy object fall on the back in 4. Levels of burst fractures are T11 in 2, T12 in 14, L1 in 19 and L2 in 4. Distractive injury in the posterior column existed at one above the burst fracture in 37 and both one above and below in 2. Horizontal fractures of the posterior elements were in the lamina in 29 patients, in the facet joints in 21 and in the spinous process in 2. Disruption of the posterior ligamentous complex was pure ligamentous in only 2 patients (5%). Preoperative neurologic statuses by the modified Frankel grading by Bradford & McBride were A in 1, B in 1, C in 3, D1 in 15, D2 in 6, D3 in 5 and E in 5. Surgical Treatment was done by anterior reconstruction in 31 patients, combined anterior and posterior reconstruction in 6 and posterior in 2. Anterior procedures were consisted of anterior spinal canal decompression and reconstruction of anterior column support using anterior instrumentation.

Results: Postoperative follow-up was 54 months (from 25 to 138 months) on the average.Solid fusion was gained in all except one stabilized by posterior procedure only, which was repaired successfully by anterior fusion. Motor function at the recent follow-up showed improvement in all except one with the modified Frankel A and 5 with E preoperatively. As to correction of kyphotic deformity, in the anterior group 23 degrees preoperative, 9.4 at postoperative and 11.6 at the final follow-up, in the combined anterior and posterior group 24.2 preoperative, 9.8 postoperative and 10.8 at follow-up, and in the posterior group 21.2 preoperative, 10.5 postoperative, and 18.6 at the final follow-up. Complications occurred in two patients. One is neurologic deterioration after posterior surgery. This was recovered by additional anterior decompression and fusion. One pseudarthrosis after posterior fusion was repaired by additional anterior fusion.

Discussion: Thoracolumbar burst fractures with distractive injury in the posterior column will not be brought about by one moment force. Considering the injury mechanism in our series, two different dynamic moment forces would be applied by vertical compression at the first phase and flexion-distraction at the second phase in a very short time. This type of injury is very unstable due to three column injuries. In conclusion, surgical treatment should fulfill the neural decompression and spinal stabilization with correction of spine deformity. In this series, anterior column reconstruction with decompression has resulted in good neural recovery and stable spine with deformity correction.

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