Biomechanical analysis of anterior stabilization techniques for different partial and total vertebral corpectomy defect models.

Introduction: Restoration of the anterior spinal profile and regular load-bearing are the main goals in treating anterior spinal defects in cases of fracture. In large vertebral defects, the use of vertebral body replacements (VBRs) is common. For isolated anterior operations, VBRs are usually combined with antero-lateral angular stable or polyaxial plates. In preclinical biomechanical testing of spinal fracture stabilizations, complete corpectomies are often applied for fracture simulation. Complete corpectomies are reproducible and easily standardized but present a maximum instability not indicated for isolated anterior instrumentation. Therefore, this study investigates the stabilizing effect of VBRs and anterior plating systems on three different vertebral body defect models.

Methods: Using 24 thoracolumbar spines, two different partial (PC 1+2) and one total corpectomy defect (CC) models were simulated and stabilized using different combinations of two VBRs and three different anterior plating systems. After anterior stabilization, range of motion (RoM) in the three main movement planes was evaluated.

Results: RoM was significantly reduced in all three motion planes for both stabilized partial corpectomy defect models compared to the stabilized complete corpectomy model and the intact specimens. The stabilized complete corpectomy defect model did not reduce RoM in flexion/extension and axial rotation compared to the intact state.

Conclusion: Both partial corpectomy models are suitable for biomechanical testing of isolated anterior stabilization. A complete corpectomy model is not suitable to test isolated anterior instrumentation, as this simulates a rotationally unstable fracture, where isolated anterior instrumentation is not indicated in clinical practice.