Influence of degenerative changes of intervertebral disc on its material properties and pathology

Objective:To investigate the material properties of normal and degenerated intervertebral discs (IVDs) and examine the effect of degenerative changes on IVD pathology. Methods:A computer-based online search was undertaken to identify English articles about material properties of IVDs published from January 1950 to 2011 in PubMed database.The retrieved keywords included material properties,intervertebral disc and degeneration.Based on the principles of reliability,advancement and efficiency, the obtained data were primarily examined,and the original source was retrieved to read the full-text.Repetitive articles were excluded.The data of material properties of normal and degenerated IVDs were summarized and analyzed by meta-analysis. Results:The data of Young’s modulus,Poisson’s ratio, shear modulus,hydraulic permeability and intradiscal pressure of normal and degenerated IVDs were obtained.Compared with normal IVDs,the Young’s modulus and shear modulus of annulus fibrosus and nucleus pulposus were higher in degenerated IVDs,the Poisson’s ratio was lower while the hydraulic permeability and intradiscal pressure were higher.Besides,the degeneration-related alterations in IVDs had an influence both on itself and other spinal structures,leading to diseases such as bulging disc, discogenic pain and spinal stenosis.Meanwhile,the heavy mechanical loading and injury indicated important pathways to IVD degeneration. Conclusions:To a certain extent,the degenerative changes of IVD influence its material properties.And the degeneration-related alterations of composition can cause structural failure of IVDs,leading to injuries and diseases.