Posterior Distraction and Instrumentation Cannot Always Reduce Displaced and Rotated Posterosuperior Fracture Fragments in Thoracolumbar Burst Fracture.

STUDY DESIGN: A retrospective clinical study.

OBJECTIVE: To determine the imaging features that can be used to predict failure of reduction of a retropulsed fracture fragment by posterior ligamentotaxis in thoracolumbar burst fractures.

SUMMARY OF BACKGROUND DATA: Posterior instrumentation and distraction with ligamentotaxis has been successfully used to shift retropulsed fragments anteriorly in thoracolumbar burst fractures. However, posterior longitudinal ligament rupture can lead to treatment failure. The exact preoperative radiographical parameters associated with failure of reduction remain unknown.

METHODS: A total of 85 patients who suffered from thoracolumbar burst fractures with significant retropulsion of fragments into the spinal canal, as confirmed by preoperative computed tomography (CT) and followed by postoperative CT, were retrospectively analyzed. Seventy-three patients (85.9%) in whom the fragments were reduced by ligamentotaxis were included in the reduced group. In 12 patients (14.1%), the fracture fragment in the spinal canal was not reduced, and these patients were included in the non-reduced group. Neurologic status was classified according to the scoring system of the American Spinal Injury Association. The displaced distance and rotation angle of the fracture fragment were measured at the fractured segment.

RESULTS: Preoperatively, the average displacement distances into the spinal canal of rotated posterosuperior fragments was 0.53 cm in the reduced group and 0.94 cm in the non-reduced group (P=0.002). The average rotation angles of the fracture fragments were 43.2° in the reduced group and 61.7° in the non-reduced group (P=0.012). "Double cortical surfaces" of the fragment were observed in the non-reduced patients. Neurological function was evaluated and recorded at the 2-year follow-up examination. There was no significant difference in the ASIA recovery grade between the two groups (P=0.668).

CONCLUSION: Displaced and rotated posterosuperior fracture fragments in thoracolumbar burst fracture cannot always be reduced by posterior ligamentotaxis. The two criteria for treatment failure that were most consistently present in our series were a displacement distance greater than 0.85 cm and a rotation angle greater than 55°.