Biomechanical characteristics of the lumbar disc after fatigue injury / 中国组织工程研究

ABSTRACT

BACKGROUND: Lumbar disc herniation is a common clinical disease, and its pathological basis is disc degeneration. Long-term mechanical load is considered to be an important cause of lumbar disc degeneration. Because the occurrence of lumbar disc herniation is strongly associated with its mechanical state, it is necessary to further study the stress/strain behavior in the lumbar disc to provide inspiration for preventing lumbar disc herniation. OBJECTIVE: To analyze the effect of fatigue loading on mechanical properties of the whole and different regions of the intervertebral disc. METHODS: The freshly slaughtered sheep lumbar intervertebral discs L1-L2, L3-L4, and L5-L6 were obtained and made into experimental samples. The experimental samples were fixed on the experimental platform through the upper and lower vertebrae, and a quasi-static compression-cyclic loading compression-quasi-static compression experiment was performed. The L3-L4 motion segment was cut parallel to the sagittal plane, and the non-contact digital image correlation technique was used to record the internal deformation of the lumbar disc during compression. RESULTS AND CONCLUSION: (1) The results showed that all lumbar intervertebral discs exhibited non-linear load-displacement and stress-strain characteristics. (2) Effect of fatigue loading The Young’s modulus of the lumbar intervertebral disc increased significantly after fatigue loading. (3) Impact of segment changes The Young’s modulus changed with segment changes as follows L5-L6 segments < L3-L4 segments < L1-L2 segments. (3) Effect of loading rate Comparing the mechanical properties under the compression rate of 0.01 mm/s and 0.1 mm/s, it could be seen that with the increase of the compression rate, the Young’s modulus of the intervertebral disc increased significantly. (5) Internal displacement distribution Fatigue loading had a significant effect on the internal displacement distribution of the lumbar disc under compression. Before fatigue loading, the axial displacement in upper afferent fiber was largest, and the radial displacement in inner afferent fiber was slightly smaller than that in outer afferent fiber. After fatigue loading, the axial displacement in upper afferent fiber was smallest, and the radial displacement in inner afferent fiber was significantly smaller than in outer afferent fiber. (6) The research work in this article has important theoretical guiding significance for preventing lumbar disc herniation in daily life.