Experimental Study of Thoracolumbar Burst Fractures. A Radiographic and Biomechanical Analysis of Anterior and Posterior Instrumentation Systems

Study Design: The efficacy of posterior instrumentations for treating thoracolumbar burst fractures to restore spinal alignment and indirectly reduce intracanal bone fragments was investigated. Also, a biomechanical study was performed to compare the mechanical stability of anterior and posterior instrumentations.

Methods: Twenty-four fresh human cadaveric thoracolumbar spine segments were used. After clinically identical L1 burst fractures were created, two posterior instrumentations were used to restore spinal alignment: 1) Harrington dual distraction rods with sleeves and 2) AO internal fixator. Radiographs and computed tomography scans were obtained to assess spinal alignment and canal dimensions. Biomechanical testing was performed in axial compression, rotation, and flexion-extension on all constructs, including anterior reconstruction with the Kaneda device.

Summary Of Background Data: Kyphosis averaged 14 degrees in the injured specimens and was corrected to 1 degree of lordosis after posterior reduction, and vertebral body height was restored to normal in most of the specimens. Reduction rate of canal compromise was 12.3% for Harrington instrumentation and 18.5% for AO internal fixator. Anterior reconstruction with the Kaneda device was more stable than the posterior instrumentation systems in all loading conditions.

Results: The posterior reduction and stabilization with posterior instrumentation provided effective restoration of the sagittal alignment. However, the reduction capability of the intracanal bone fragments was distinctly limited.

Conclusions: The anterior reconstruction method permits effective decompression of the spinal canal and offers superior mechanical stability compared with the indirect decompression and stabilization of posterior instrumentation.