Biomechanical evaluation of the stability of thoracolumbar burst fractures.

ABSTRACT

STUDY DESIGN: The decision to treat thoracolumbar burst fractures in neurologically intact patients either surgically or nonoperatively depends largely on whether the fracture is clinically stable. This study evaluated the relative contributions of the anterior, middle, and posterior columns to spinal stability by way of in vitro experimentation and supplemental analysis of patients with nonoperatively treated burst fractures. METHODS: An L1 burst fracture model was used to evaluate the contribution of the three columns of the spine to resisting imposed flexion deforming forces. Six spines were tested to a gross bending flexion angle of 25 degrees. Changes in vertebral motion across the site of injury were measured and compared. In addition, a summary of our recent clinical experience with nonoperatively treated burst fractures is presented and correlated with the study's laboratory findings. RESULTS: T12-L2 motion measurements after vertebral and ligamentous disruption revealed a statistically significant increase in motion upon anterior and added posterior column compromise, but not for added middle column disruption. Review of the clinical series revealed that burst fractures with anterior and middle column compromise but an intact posterior column were stable and healed satisfactorily. CONCLUSIONS: The data suggest that the condition of the posterior column, not the middle column, is a better indicator of burst fracture stability. It is proposed that the classic burst fracture (anterior and middle column compromise) is a stable injury that, in the absence of neurologic deficit, can be managed nonoperatively.