When the thoracic spine must be stabilized surgically, pedicle screws may be used. The pedicle is a portion of bone just below the facet joints of the spine. The pedicle connects the main body of the vertebra to the bony ring that protects the spinal cord. Using screws to hold the vertebrae in place is called instrumentation.
Placement of the screws is a technically challenging task for the surgeon. The screw can perforate (poke through) nerves, blood vessels, and even the spinal cord. Computer assistance to guide the surgeon has helped reduce these problems.
In this study, neurosurgeons at five major hospitals compare the use of two different image guidance systems. The first method used was virtual fluoroscopy (Fluoro-Nav by Medtronic).
The second navigation system was the new isocentric C-arm-based device (Iso-C). All patients were undergoing pedicle screw placement. Surgery was needed to stabilize the spine in 37 cases of trauma, degenerative disease, or bone tumor.
The authors used computer analysis to determine what a perfect screw placement would be. This was compared with CT scans showing the actual placement. The accuracy of screw placement was then compared using the two different navigational systems.
The type and amount of perforation with each system was identified. There was no difference in the overall rate of unintended or unsafe perforations between the two devices.
The risk of perforation increases anytime the pedicle is small. In those cases, even the smallest screw may be larger than the pedicle. The number of spinal levels treated with instrumentation did not increase the risk of perforation.
The authors concluded that both image-guidance systems provided safe and accurate results. The surgeon’s knowledge of anatomy and careful surgical technique aided by image guidance resulted in excellent outcomes.