Accuracy of fluoroscopically assisted laser targeting of the cadaveric thoracic and lumbar spine to place transpedicular screws

A simple and inexpensive method was developed to obtain a coaxial view of t he pedicles to assist with screw insertion. The authors evaluated the accur acy of this device to place transpedicular vertebral screws in a human adul t cadaver model. A dual radiation targeting system, a laser targeting syste m for fluoroscopically guided procedures was developed to provide an accura te surface entry point and angle of approach to radiographic landmarks. Aft er fluoroscopic cross-hair target localization of the coaxial view of the p edicle, X-ray radiation is turned off and the laser beam allows the surgeon to guide the screw through the pedicle. Nine cadaver spines were removed a nd mounted. Three surgeons, inexperienced in the technique of pedicle screw placement, fitted instruments to 184 pedicles between L5 and T5. A total o f 83 lumbar and 101 thoracic pedicles underwent screw placement, After spec imen dissection, the degree and location of any screw perforation were meas ured by direct inspection. Three screws perforated a pedicle, for an error rate of 1.6%. Two lumbar screws (2.4% error) and one thoracic screw (1% err or) perforated the pedicle. No screw was more than 1 mm outside the pedicle . Five other screws, four in the thoracic spine and one in the lumbar spine (error rate of 2.7%) were directed too far laterally and perforated the la teral vertebral body. This low rate of pedicle wall cortical perforation by inexperienced surgeons compares favorably with much higher pedicle perfora tion rates by experienced surgeons when no imaging was used. in conclusion, this in vitro model using a dual radiation targeting system-assisted with the accurate placement of transpedicular vertebral screws with minimal radi ation exposure.