In vitro biomechanical characteristics of the spine: a comparison between human and porcine spinal segments

Study Design: An in vitro study on human and porcine multilevel spinal segments. Objective: To compare human and porcine thoracolumbar spinal segments with respect to their biomechanical characteristics and the effects of creep, recovery, and removal of ligaments and posterior parts on the biomechanical characteristics. Summary of Background Data: Availability of human cadaver spines for in vitro testing of new spinal implants and surgical procedures is limited. Therefore, it is important to search for animal models with representative biomechanical characteristics. Methods: A total of 6 human and 6 porcine cadaver spines were dissected in multilevel spinal segments. Pure moments were applied to each segment in flexion/extension, lateral bending, and axial rotation. Creep tests were performed for 30 minutes in 4 creep directions, followed by cyclic tests, a recovery period of 30 minutes, and a series of cyclic tests after removal of ligaments and posterior parts. The range of motion, neutral zone (NZ), and neutral zone stiffness (NZStiff) were calculated from the acquired load-displacement data and results were compared between human and porcine segments. Results: The porcine segments generally had significantly higher absolute values for range of motion and NZ and significantly lower absolute values for NZStiff than the human segments in all directions. The effects of creep and recovery were quite similar in the higher and midthoracic regions of the spine. The influence of removal of ligaments was the same in human and porcine segments. After removal of posterior parts, the lower thoracic porcine spine behaved quite similar to the lumbar human spine. Conclusion: This study showed that the porcine spine can be a good biomechanical model for the human spine in specific situations. The question if the porcine spine can be used to predict the behavior of a human spine depends mainly on the application and the research question. © 2010, Lippincott Williams & Wilkins