[Computer-assisted surgery (CAS) in transpedicular lumbar fusion. Experiences of the Spinal Neurosurgery Department]

A well-known problem occurring with lumbar fusion is the incorrect placement of the pedicular screws. Previous studies have shown a rate of incorrect insertion of the screws ranging from 10 to 40%. An incorrectly inserted screw with medial perforation through the pedicle may cause an acute injury of the root passing medially to the pedicle. In case of wrong laterally placed screw the root exiting along the lateral wall of pedicle can be damaged. As a rule, a neurological deficit due to such an injury is irreversible. Vascular lesions are much rarer. Screws malposition, no matter in which direction the insertion should be wrong, leads very often to failed fusion. To reduce the rate of incorrectly placed transpedicular screws, computed tomography based navigation has been introduced. It allows the surgeon multidimensional control of the screw position in virtual reality and real time during insertion. The experience with the first 109 patients in which transpedicular lumbar fusion was performed this way in the Neurosurgical Dpt of the Spine Unit in the Schulthess Clinic in Zurich is described. The computed assisted surgery (CAS) takes slightly more time than the conventional procedure. The significantly increased accuracy of pedicle screw insertion repays this disadvantage generously.