Comparison of animal discs used in disc research to human lumbar disc

Study Design. Experimental measurement and normalization of in vitro disc axial compression mechanics and glycosaminoglycan and water content for several animal species used in intervertebral disc research. Objective. To compare normalized axial mechanical properties and glycosaminoglycan and water content from other species to those of the human disc to aid in selection and interpretation of results in animal disc studies. Summary of Background Data. There is a lack of mechanical and biochemical comparative data from animal intervertebral discs with respect to the human disc. Methods. Intervertebral disc axial mechanical properties, glycosaminoglycan, and water content were evaluated for 9 disc types in 7 mammalian species: the calf, pig, baboon, sheep, rabbit, rat and mouse lumbar, and the cow and rat tail. Disc area and height were used for calculation of the normalized mechanical parameters. Glycosaminoglycan content was normalized by dry weight. Results. Many directly measured mechanical parameters varied by orders of magnitude. However, these parameters became comparable and often did not show significant differences after geometric normalization. Both glycosaminoglycan and water content revealed similarity across species. Conclusion. Disc axial mechanics are very similar across animal species when normalizing by the geometric parameters of disc height and area. This suggests that the disc tissue material properties are largely conserved across animal species. These results provide a reference to compare disc axial mechanics and glycosaminoglycan and water composition of experimental animal models to the human lumbar disc, to aid in both selection and interpretation of experimental disc research.