Biomechanical analysis of a multi-level corpectomy model: a comparison of strut graft reconstruction alone or concurrent with anterior cervical plating

In this model, multi-level cervical corpectomy resulted in decreased stiffness and increased motion across the operated region relative to the harvested spine. Addition of a strut-graft produced minimal gain in stiffness, although there was a decrease in the motion across the operated region. Presumably, the distraction of ligamentous tissue in the operated region was responsible for a "re-balancing" of angular displacement among the various levels. No difference was detected in the work measures between the corpectomized and grafted spines. Addition of a plate to the strut-grafted spine decreased the motion across the operated region to near that of the harvested specimen. The extensional stiffness/stability of strut-graft and plated spine was restored to the harvested spine state. These findings would suggest that compensation occurred at the adjacent motion segments. Compensatory increased motion at the adjacent motion segments may explain clinical reports of late increased degenerative changes at these levels (C.G. Paramore et al., 1996). These results support the notion that anterior strut-grafting alone may be insufficient stabilization following multi-level corpectomy and that anterior cervical instrumentation provides additional stability to the spine which may help prevent graft failure during extension loading.