Spinal Cord Stress After Anterior Cervical Diskectomy and Fusion: Results from a Patient-Specific Finite Element Model.

Degenerative cervical myelopathy (DCM) is the commonest cause of cervical spinal cord dysfunction in older adults and is characterized by spinal cord compression and stress during neck motion. Although surgical decompression eliminates static spinal cord compression, cord stress resulting from flexion-extension motion of the spinal column has not been determined for single and multi-level surgical interventions. The effect of surgery on spinal cord stress is expected to change with the number of surgical levels as well as patient-specific anatomy. Using a MRI-derived patient-specific finite element model, we simulated 1-, 2- and 3-level anterior cervical diskectomy and fusion (ACDF) surgery for DCM. A substantial decrease in spinal cord stress at the level of spinal cord decompression was noted in all simulations. This was associated with a considerable increase in spinal cord stress rostral to the surgical level, and the magnitude of stress was higher in multi-level surgery. Increased spinal cord stress at the rostral adjacent segment correlated with increased segmental range of motion (r = 0.69, p = 0.002) and disk pressure (r = 0.57, p = 0.05). Together, these results indicate that ACDF for DCM is associated with adverse spinal cord stress patterns adjacent to the fusion construct, and further research is needed to determine if the altered stress is associated with clinical outcomes after surgery for DCM.