The development of an improved physical surrogate model of the human spinal cord--tension and transverse compression.

To prevent spinal cord injury, optimize treatments for it, and better understand spinal cord pathologies such as spondylotic myelopathy, the interaction between the spinal column and the spinal cord during injury and pathology must be understood. The spinal cord is a complex and very soft tissue that changes properties rapidly after death and is difficult to model. Our objective was to develop a physical surrogate spinal cord with material properties closely corresponding to the in vivo human spinal cord that would be suitable for studying spinal cord injury under a variety of injurious conditions. Appropriate target material properties were identified from published studies and several candidate surrogate materials were screened, under uniaxial tension, in a materials testing machine. QM Skin 30, a silicone elastomer, was identified as the most appropriate material. Spinal cords manufactured from QM Skin 30 were tested under uniaxial tension and transverse compression. Rectangular specimens of QM Skin 30 were also tested under uniform compression. QM Skin 30 produced surrogate cords with a Young's modulus in tension and compression approximately matching values reported for in vivo animal spinal cords (0.25 and 0.20 MPa, respectively). The tensile and compressive Young's modulus and the behavior of the surrogate cord simulated the nonlinear behavior of the in vivo spinal cord.