Structure and mechanical characteristics of spinal dura mater in different segments of sheep's spine

Abstract

To clarify the structure and biomechanical characteristics of the dura mater of the cervical, thoracic, and lumbar segments of sheep, in order to provide a theoretical reference for the study of artificial dura mater. Five adult male white sheep were sacrificed. The dura mater of C 5, T 10, and L 3 planes were obtained. The histological HE staining was used to observe the internal structure and the thickness of dura mater; the inner and outer surfaces morphology of the dura was observed by scanning electron microscopy (SEM); transmission electron microscopy (TEM) was used to observe the internal structure of dura mater and to measure the diameter of collagen fibers in each part of dura mater. The dura mater of C 6, C 7, T 11, T 12, L 4, and L 5 planes were taken for uniaxial biomechanical test, and modulus of elasticity, tensile strength, and elongation at break were measured. HE staining showed that the thickness of the cervical, thoracic, and lumbar dura mater gradually decreased, and the thickness of the dura mater was (268.19±15.91), (198.16±27.25), (103.74±21.54) μm, respectively, and the differences were significant ( P<0.05). SEM observation showed that there were more collagen fibers and fewer cells on the inner surface of the dura mater, while more cells were distributed on the outer surface, and the cells on the inner and outer surface were stretched along the longitudinal axis. TEM observation showed that the collagen fibers in the dura mater were interlaced and arranged in layers. The collagen fibers in the lamina were arranged in the same direction, and the collagen fibers between the lamina were arranged vertically. The diameters of collagen fibers in the cervical, thoracic, and lumbar dura mater were (68.04±21.00), (64.54±20.64), (60.36±19.65) nm, respectively, and the differences were not significant ( P>0.05). Uniaxial biomechanical tests results showed that there was no significant difference in modulus of elasticity, tensile strength, and elongation at break between the axial and transverse dura mater of the cervical dura mater ( P>0.05); the axial data of thoracic and lumbar segments were significantly larger than the transverse data ( P<0.05). The axial modulus of elasticity, tensile strength, and elongation at break of the dura mater of the cervical, thoracic, and lumbar dura mater were significantly different ( P<0.05) from the transverse ones, and showing a decreasing trend. Among them, the ratio of axial and transverse modulus of elasticity of cervical and thoracic dura were significantly smaller than that of lumbar segment ( P<0.05), and there was no significant difference between cervical segments and thoracic segments ( P>0.05). The thickness of dura mater in sheep decreased gradually from head to tail. There are more collagen fibers and fewer cells on the inner surface of dura mater, while the outer surface of dura mater is covered by cells. The collagen fiberboard layers in the dura mater are arranged alternately, and have obvious anisotropic biomechanical characteristics, and the anisotropic biomechanical characteristics get more significant from the head to the tail.