Pittsburgh, November 15, 2007 -- Spinal instrumentation is a well established treatment for a multitude of spinal disorders. Pedicle screw fusion along the entire spinal axis is a very common operation. The tools and instrumentation available now have been perfected over the last decade, but the placement of the instrumentation still demands high technical skills and precise spatial orientation by the neurosurgeon.

With increased acceptance and use of spinal instrumentation it was seen that routine radiography such as fluoroscopy to assess pedicle screw placement was not reliable. The rate of penetration of the pedicle cortex by an inserted screw ranged from 21 to 31% in some studies. The disadvantage of conventional radiography in orienting the surgeon to the unexposed spinal anatomy is that it displays only two planar images.

Image-guided spinal navigation allows the surgeon to identify the non-visualized anatomy in three planes of any selected point in the surgical field. CT image-guided spinal navigation provides the spine surgeon with superior imaging data compared with conventional devices such as fluoroscopy. Image-guided spinal navigation can improve the speed, accuracy, and precision of complex spinal surgery eliminating the need for cumbersome intraoperative fluoroscopy.

UPMC Presbyterian has installed an intraoperative CT suite to allow state of the art intraoperative imaging. Recently, our spine team has been able to perform complex spinal reconstructions using intraoperative CT imaging and spinal navigation.

(top) Neurosurgeon places image-guidance probe on pedicle entry point and confirms trajectory by observing reformatted views of intraoperative anatomy displayed on navigation system. (below) Image-guided operating suite with CT-scanner in background and image-guidance working station in front.

For a pedicle screw fusion with image guidance the patient is positioned on the operative CT scanner table. The surgical exposure of the anatomical landmarks is performed in routine fashion. Reference markers, fiducials, are placed in rigid bone landmarks immediately after the surgical exposure. This preserves the spinal and anatomical landmarks that facilitate an easy and accurate registration. Next, an intraoperative multiplanar CT-scan is obtained without moving the patient out of his surgical position. This takes less than 60 seconds. A 3D volume data-set of contiguous axial CT scans is obtained and transferred to the image-guidance work station. An image guided tracker is attached to the spinous process and then registration is accomplished. The system is accurate to 1mm using this technique.

The image guided tools are now able to show the exact location of any point in the exposed spine. Coronal, sagittal, axial, and 3D images are available to the surgeon in real time. The orientation of each pedicle to be instrumented can be assessed rapidly and accurately. Any errors in trajectory or entry point selection can be determined and corrected by adjusting the position of the probe and the drill guide through which it passes. Once the instrumentation has been placed confirmation by a second intraoperative CT-scan is obtained.

The UPMC intraoperative CT suite solves the traditional problems associated with utilizing image guidance in the spine. This represents a significant improvement to the existing technology of spinal instrumentation.