Analysis of the Risk Factors for Unfavorable Radiologic Outcomes after Fusion Surgery in Thoracolumbar Burst Fracture : What Amount of Postoperative Thoracolumbar Kyphosis Correction is Reasonable?

Abstract

Objective: The aims in the management of thoracolumbar spinal fractures are not only to restore vertebral column stability, but also to obtain acceptable alignment of the thoracolumbar junction (T-L junction) to prevent complications. However, insufficient surgical correction of the thoracolumbar spine would be likely to cause late progression of abnormal kyphosis. Therefore, we identified the surgical factors that affected unfavorable radiologic outcomes of the thoracolumbar spine after surgery.

Methods: This study was conducted in a single institution from January 2007 to December 2013. A total of 98 patients with unstable thoracolumbar spine fracture were included. In these patients, fixation was done through transpedicular screws with rods by three surgical patterns. We reviewed digital radiographs and analyzed the images preoperatively and postoperatively during follow-up visits to compare the change of the thoracolumbar Cobb angle with radiologic parameters and clinical outcomes. The unfavorable radiologic group was defined as the patients who were measured as having greater than 20 degrees of thoracolumbar Cobb angle on the last follow-up, or who underwent kyphotic progression of thoracolumbar Cobb angle greater than 10 degrees from the immediate postoperative state to final follow-up, or who had overt instrument failure with/without additional surgery. We assessed the risk factors that affected the unfavorable radiologic outcomes.

Results: We had 43 patients with unfavorable radiologic outcomes, including 35 abnormal thoracolumbar alignments and 14 instrumental failures with/without additional surgery. The multivariate logistic regression test showed that immediate postoperative T-L junction Cobb angle less than 10.5 degrees was a statistically significant risk factor, as well as the presence of osteoporosis (p=0.017 and 0.049, respectively).

Conclusion: Insufficient correction of thoracolumbar kyphosis was considered to be a major factor of an unfavorable radiological outcome. The spinal surgeon should consider that having a T-L junction Cobb angle larger than 10.5 degrees immediately after surgery could result in an unfavorable radiological outcome, which is related to a poor clinical outcome.

Keywords: Spinal injuries ∙ Thoracic vertebrae ∙ Kyphosis ∙ Risk factors.

Fig. 1.

Lateral plain postoperative radiographs of three patients with L1 burst facture treated by three surgical techniques (A-C).

Fig. 2.

Postoperative radiographs showing the overall thoracolumbar Cobb angle for a case from each of the radiologic groups (left, unfavorable radiological outcome group; right, favorable radiological outcome group), which is a measured angle A between the superior endplate of T10 and the inferior endplate of L2.

Fig. 3.

The receiver operating characteristics (ROC) curve analysis for favorable radiological outcomes, the area under the ROC curves was 0.836 (95% confidence interval 0.75–0.92). The Cutoff value of immediate postoperative T-L junction Cobb angle is 10.5 degrees (arrow). The sensitivity and specificity were 82% and 72%, respectively.