Biomechanical comparison of instrumentation techniques in treatment of thoracolumbar burst fractures: a finite element analysis

There are several surgical techniques currently employed to treat thoracolumbar burst fractures, including anterior fixation, posterior fixation, or combined anterior-posterior fixation. Biomechanical analysis of the various types of surgical techniques is therefore critical to enable selection of the appropriate surgical method for successful spinal fusion. However, the effects of the various spinal fusion techniques on spinal stiffness have not been clearly defined, and the strengths and weaknesses of each fusion technique are still controversial. The biomechanical effects of increasing the number of anterior rods and removing the mid-column in anterior fixation, posterior fixation, and combined anterior-posterior fixation on spinal stiffness in thoracolumbar burst fractures was investigated. Finite element analysis was used to investigate the effects of the three fusion methods on spine biomechanics because of its ability to control for variables related to the material and experimental environment. The stiffness of the fused spinal junction highly correlates with the selection of an additional posterior fixation. The mid-column decompression showed a significant change in stiffness, although the effect of decompression was much less than that with the application of posterior fixation and the anterior rod number. In addition, two-rod anterior fixation without additional posterior fixation is able to provide enough spinal stability; and one-rod anterior fixation with posterior fixation yields better results in regard to preventing excessive motion and ensuring spinal stability. The present study shows that careful consideration is necessary when choosing the anterior rod number and applying posterior fixation and mid-column decompression during surgical treatment of thoracolumbar burst fractures.