Computer assisted pedicle screw fixation: clinical experience with a newly developed software

We have used software, recently developed at Cochin University of Science and Technology, to perform computer assisted pedicle screw placement in forty pedicles of ten patients with fractured thoracolumbar vertebrae from January 2002 to February 2004. A pre-operative CT scan section at the pedicle level is taken one vertebra above and one below the involved vertebra. The dicom image is converted into a bitmap image and reference lines are drawn through the transverse processes and the spinous processes. The screw trajectory is drawn in the image at the most suitable path of the pedicle. Intraoperatively reference pins are placed exactly at the same areas in the transverse processes and the spinous processes. The intraoperative image is live captured using a camera and is matched with the preoperative image and the awl is advanced into the pedicle corresponding to the screw trajectory in the CT image. Out of forty pedicles instrumented in ten patients using computer assistance, the pedicle wall violation as demonstrated with 1 mm thin CT scans was less than AMIOT Grade 2. Ideal placement was noted in 80% and clinically insignificant perforation (Grade 2&3) in the rest. Computer assisted pedicle screw fixation appears to be a good technique for the accurate placement of pedicle screws in fractured vertebrae.