Are sheep spines a valid biomechanical model for human spines?

Study Design. Range of motion, neutral zone, and stiffness parameters of the complete cervical, thoracic, and lumbar sheep spine were determined in flexion and extension, axial left/right rotation, and right/left lateral bending. Objectives. To determine quantitative biomechanical properties of the sheep spine and compare them with those from the human spine. Summary of Background Data. Sheep spines often serve as a model for experimental in vivo and in vitro studies in spine research, but few quantitative biomechanical data from sheep spines for comparison with human specimens are available. Methods. Complete spines were sectioned into Single-joint segments and tested in a spine tester under : pure moments in the three main anatomic planes. Results. The craniocaudal variation in range of motion in all load directions was qualitatively similar between sheep spines and values reported in the literature for human specimens. Conclusions. Based on the biomechanical similarities of sheep and human spines demonstrated in this study, it appears that the use of the sheep spine, which already includes evaluation of surgical techniques and bone healing processes, might be extended to spinal implants.