Comparison of animals used in disc research to human lumbar disc geometry

Study Design. Measurement and normalization of disc geometry parameters for several animal models used in disc research. Objectives. To compare normalized values of disc geometry to the human disc geometry to aid in the selection and interpretation of animal model studies. Summary of Background Data. Animal models are widely used to study intervertebral disc degeneration and to evaluate disc treatment methods because of the availability of the tissue, the decreased variability between subjects compared with humans, and the feasibility to perform in vivo experiments. There is a general lack of comparative data with respect to the human disc analog for animal models. Methods. The disc height, lateral width, AP width, area, and the nucleus pulposus lateral width, AP width, area, and centroid offset were all measured and normalized by 2 scaling factors, lateral width and disc area, for comparison to human. Results. The species studied were ranked according to the average percent deviation of the normalized disc height, AP width and nucleus pulposus area from human geometry as: mouse lumbar ( 12%), rat lumbar ( 15%), mouse tail ( 18%), baboon ( 19%), bovine tail ( 22%), rabbit ( 26%), sheep ( 31%), and rat tail ( 46%). Conclusions. This paper provides a reference to compare disc geometries of experimental animal models to the human lumbar disc, to aid both in interpretation of and in planning for experimental disc research, and to provide normalized disc geometry parameters for computational models.