BIOMECHANICAL EVALUATION OF THE STABILITY OF THORACOLUMBAR BURST FRACTURES

Study Design. The decision to treat thoracolumbar burst fractures in n eurologically intact patients either surgically or nonoperatively depe nds largely on whether the fracture is clinically stable. This study e valuated the relative contributions of the anterior, middle, and poste rior columns to spinal stability by way of in vitro experimentation an d supplemental analysis of patients with nonoperatively treated burst fractures. Methods. An L1 burst fracture model was used to evaluate th e contribution of the three columns of the spine to resisting imposed flexion deforming forces. Six spines were tested to a gross bending fl exion angle of 25-degrees. Changes in vertebral motion across the site of injury were measured and compared. In addition, a summary of our r ecent clinical experience with nonoperatively treated burst fractures is presented and correlated with the study's laboratory findings. Resu lts. T12-L2 motion measurements after vertebral and ligamentous disrup tion revealed a statistically significant increase in motion upon ante rior and added posterior column compromise, but not for added middle c olumn disruption. Review of the clinical series revealed that burst fr actures with anterior and middle column compromise but an intact poste rior column were stable and healed satisfactorily. Conclusions. The da ta suggest that the condition of the posterior column, not the middle column, is a better indicator of burst fracture stability. It is propo sed that the classic burst fracture (anterior and middle column compro mise) is a stable injury that, in the absence of neurologic deficit, c an be managed nonoperatively.