Ideal animal spine models have been used by researchers to compare and evaluate the biomechanical behavior of spine following surgery and implantation due to the growing difficulty in obtaining fresh human spine specimens. Availability and resemblance of sheep and baboon spines to human spine make them suitable for use in biomechanical studies; however the literature on biomechanics of baboon and sheep spine compared to human spine is sparse. In the present study finite element method was used to compare the load transfer and load-displacement characteristics of L3-L4 sheep, baboon and human spines.

Lumbar spondylolisthesis is an extension of spondylolysis in which breakage of the vertebrae occurs at the pars interarticularis causing the vertebrae to slip forward. Spondylolisthesis is seen in both younger and older populations with most lesions occurring at the L4-L5 or L5-S1 level. Although the forward slippage of the vertebra does not usually exceed 30% of the body’s anterior-posterior width, possible spinal stenosis and nerve impingement may lead to severe pain and other complications. The purpose of this study is to determine the effect of single level and bi-level dynamic stabilization in reducing the spondylolisthesis. We used the finite element model for this purpose since it is not practical to procure specimens with spondylolisthesis for an experimental investigation.