摘要：The human spine shortens approximately by 1% ofits height during the daily activities and returns to its primary height during the night rest. Cyclic loading is important in order to ensure diffusion and convention of thenutrients and metabolites within the intervertebral discs. Onthe other hand, cyclic loading could lead to the damage ofthe intervertebral discs and the vertebra bodies if the magnitude and frequency of the loads applied to the spine exceed the allowable limits. As most of the in vitro studies thatinvestigate the influence of cyclic loading deal with functional spinal units consisting of single intervertebral disc thepurpose of this study is to investigate an influence of cycliccompression and flexion on the structural integrity and geometrical parameters of the spinal specimens consisting ofmore than one intervertebral disc.Two specimens consisting of four adjacent vertebrae and three intervertebral discs were scanned by usingcomputed tomography then loaded with combined cycliccompression and flexion and then scanned for the secondtime in order to capture the current condition of the specimens. Obtained images were used to evaluate the changesof structural integrity and geometrical parameters of thediscs.A significant decrease of the specimen height wasobserved during loading, mainly due to the loss of the fluidcontent within intervertebral discs. In total, the difference ofthe height of the two specimens immediately after the loading was 1.577 mm. No obvious damage to the specimenswas observed when comparing images before and after theloading. A statistically significant differences between theheight of the intervertebral discs before and after loading inboth the first specimen (p = 0.0224) and the second specimen (p = 0.0155) were calculated with the lowest disc ofboth specimens decreasing the most and obviously losingthe highest water content. The cross-sectional area of thelowest disc in both specimens also decreased the most. Thisonce again confirms that lower part of the spine such as intervertebral discs L4-L5 and L5-S1 are the least prone to theinjuries and degeneration due to disturbed nutrition and lossof water content.
