Intramedullary Strain During Neck Extension is Associated with Microstructural Spinal Cord Injury in Degenerative...

Intramedullary stress and strain during neck motion have been proposed as a cause of spinal cord damage in degenerative cervical myelopathy (DCM). We aimed to determine this relationship using patient-specific modeling and advanced MRI.

Twenty DCM patients underwent 3D finite element modeling of the cervical spine and spinal cord. We quantified von Mises stress and maximum principal strain at the level of maximum cord compression and across the entire cervical spinal cord during simulated neck flexion and extension. Pre-surgical MRI included T1-weighted, T2-weighted, and DTI. DTI indices were measured at the maximum compression level and across the entire cervical cord (C2-C7). Associations between FEM metrics and DTI indices were evaluated using stepwise multivariable linear regression.

Twenty DCM patients (13 females, 7 males; median age 64 years; 37-76 years) were enrolled. The median preoperative modified Japanese Orthopedic Association score was 13 (9-17). The most common cervical spine level of maximum compression was C5-C6 (40%, n = 8), followed by C6-C7 (25%, n = 5), C4-C5 (20%, n = 4), and C3-C4 (15%, n = 3). Maximum spinal cord strain during neck extension was associated with lower FA (B = - 2.1, R² = 0.32, p = 0.01), higher mean diffusivity (B = 4.8, R² = 0.21, p = 0.04) and radial diffusivity (B = 4.9, R² = 0.29, p = 0.01) across the whole spinal cord.

Intramedullary strain during neck extension correlates with microstructural spinal cord injury in patients with DCM. Patient-specific biophysical modeling highlights the impact of intramedullary strain during neck motion on the pathophysiology of DCM.