A biomechanical investigation of the effect of additional transpedicular fixation of the corpectomied vertebrae on stability: a calf spine model

Objectives: To investigate whether an additional transpedicular screw fixation of the injured vertebra would increase the stability of posterior fixation. Methods: Ten fresh calf spine segments, each containing three motion segments, were obtained and anterior corpectomy was performed at the middle vertebra of each specimen. Posterior spinal instrumentation was performed in all specimens. In one group (n=5), screws were placed into the pedicle one level above and below the corpectomy level. In another group (n=5), additional transpedicular fixations were made at the corpectomy level. Stability of both groups was tested using compressive loads. The results were statistically evaluated using Mann-Whitney U-Wilcoxon rank sum W test. Results: The model showed not only that additional screw placement at the injury level did not contribute to the stability of the posterior stabilization of the vertebrae but also that screws applied to the corpectomied vertebra gave rise to additional injury to the pedicles. Conclusion: Due to small sample size and since only compressive forces were studied, further studies are required on flexion, extension, lateral bending, and torsional forces and the results should be supported by clinical studies.