Exploring the effect of displacement rate on the mechanical properties of denticulate ligaments through uniaxial tensile testing

Denticulate ligaments play a key role in stabilizing the spinal cord (SC). Accurate representation of these structures in finite element modelling, whether in quasi-static or dynamic conditions, is essential for providing biofidelic responses. Therefore, understanding, characterizing and comparing the tensile mechanical properties of denticulate ligaments at different loading velocities is crucial. A total of 38 denticulate ligament samples at different cervical levels (anatomical levels from C1 to C7) were obtained from 3 fresh porcine SCs and 86 uniaxial tensile tests were performed immediately after dissection using an electro-mechanical testing system equipped with a 22 N loadcell. The mechanical tests included 10 cycles of preconditioning and a ramp with displacement rates of 0.1 mm s^-1, 1 mm s^-1 and 10 mm s^-1. Bilinear piecewise fitting and trilinear piecewise fitting were performed to determine the elastic modulus and maximum stress and strainof the samples. While no significant differences in the mechanical behavior of the denticulate ligaments were found across the different displacement rates, notable variations were found between spinal levels, with a significantly higher elastic modulus at the lower cervical levels.