Effects of tracking adjacent vertebral bodies during image guided pedicle screw surgery

Abstract

An optical position sensor was used to measure the motion of L3–L5 in a pig spine under ventilation, transverse loading, and during use of the pedicle awl. The spine of an intact, ventilated pig was first exposed to reveal the lumbar vertebrae and schantz pins with optical trackers were attached to the spinous processes. The motion of the three vertebrae was monitored during ventilation and then while loading was applied. Transverse loads of 10 N were applied to each vertebra in turn, and the corresponding motion observed. Flexion-distraction followed by three column injuries were simulated between L4 and L5 and the measurements repeated. While motion due to breathing was similar for all vertebra the segments moved by differing amounts once loading was applied. Once loading was released, the segments appeared to return to the pre-loaded positions. Destabilization of the spine, by simulating ligamentous injury, caused an increase in the amount of motion, but the inter-segmental position returned to preloaded positions.