Three dimensional kinematics of the thoracolumbar spine as quantified by a novel in vivo/in vitro active/passive robotic simulator

Low back pain is one of the leading causes of missed work. Surgical intervention is an option to those who have failed conservative therapy. The current gold standard of surgical procedures is bony fusion. Long term follow up of fusion patients has identified adjacent level disease as a complication. New motion preserving technologies aim to eliminate harmful effects on adjacent levels but have not been confirmed with long term clinical trials. In vitro testing provides repeatability for relative comparison between treatments, but the clinical relevance remains questionable without in vivo loads and motions. We have developed a novel in vivo/in vitro method using active motion to characterize the motion of the thoracolumbar spine using a robotic simulator. Preliminary results indicate a reduction in motion at the operative and super-adjacent level while motion is increased at all other levels. This may be compensation for the reduced motions at the operative and adjacent level.