Mechanical differences of anterior and posterior spinal nerve roots revealed by tensile testing

Cervical spondylotic myelopathy can damage the nerves and structures of the subarachnoidal canal. The spinal cord is attached to the subarachnoidal canal via structures such as nerve roots (NR), which play an important role in its positioning and can be affected by cervical spondylotic myelopathy Understanding the tensile mechanical properties of nerve roots is therefore crucial. A total of 37 swine nerve samples (15 bundles, 12 posterior roots, and 10 anterior roots) were mechanically tested within 12 h of sacrifice by a tensile test on a Mach 1 system (Biomomentum, Montreal, Canada) equipped with a 17 N load cell. Bi-linear piecewise fitting was performed to determine the elastic modulus, maximal strain and stress at failure, as well as the coefficients of the 1st- and 3rd-order Ogden models. Additionally, a sensitivity analysis on the Ogden coefficients was performed. The elastic modulus for the bundles, posterior roots, and anterior roots were 3.7 ± 3.1 MPa, 0.23 ± 0.18 MPa, and 0.31 ± 0.27 MPa, respectively. Significant differences (P < 0.05) were found between the bundles and the anterior/posterior roots. Coefficients for the 1st-, 2nd- and 3rd-order Ogden models were provided for each type of sample. Nerve roots have different properties depending on their types. The 1st-order Ogden model may be used to model the mechanical properties of NR using constitutive laws.