Association between extent of simulated degeneration of C5-C6 disc and biomechanical parameters of a model of the full cervical spine: a finite element analysis study

Purpose: To delineate the association between extent of degeneration of the disc at C5-C6, simulated in a model of the full cervical spine, and biomechanical responses of the model. Methods: A validated three-dimensional model of an intact, healthy, adult full cervical spine (C1-C7) was constructed. This model was then modified to create three models simulating mild, moderate, and severe grades of degeneration of the disc at C5-C6. For each of these four models, we used the finite element analysis method to obtain three biomechanical parameters at various tissues in the model, under seven different physiologically relevant loadings. Results: For each of the biomechanical parameters, the results were expressed as relative change in its value when a specified combination of simulated degeneration model and applied loading was used, with respect to the corresponding value in the intact model. We introduced a new measure, which we designate the composite biomechanical performance index (CBPI), whose value incorporates all of the aforementioned relative changes. Conclusions: We found that CBPI increased with increase in the severity of disc degeneration simulated. The clinical relevance of CBPI should be addressed in future work.