Use of a transpedicular drill guide for pedicle screw insertion in the thoracic spine.

A transpedicular drill guide (TDG) was designed to assist in the safe placement of pedicle screws in the thoracic spine. In a preliminary study, pilot holes were drilled into the pedicles (T1 to T12) of eight anatomical models in order to compare the conventional anatomical technique to the TDG. Visual inspection of the drilled pedicles was performed. Subsequently in a cadaveric study, pilot holes were made using the TDG in the thoracic spine (T1 to T11) of one human cadaver before inserting 4.5 mm diameter screws. CT scan followed by visual inspection of the cadaveric spine was performed to evaluate the position of the screws. With the anatomical models, 19 of 96 (19.8%) holes drilled using the TDG and 64 of 96 (66.7%) holes drilled using the anatomical technique violated the pedicle wall (p<0.001). The TDG reduced the rate of medial perforation. Ninety-nine percent of the pilot holes made with the TDG were within 2 mm from the pedicle wall compared to 79.2% for the anatomical technique. In the cadaveric study, one of the 22 (4.5%) screws violated the medial wall of the right T1 pedicle by less than 1 mm. No screw penetrated the anterior vertebral cortex, nor the lateral, superior or inferior pedicle wall. The TDG is easy to use and can decrease the incidence of misplaced thoracic pedicle screws. The TDG could be used alone as an alternative to navigation systems in certain applications or with fluoroscopy during thoracic pedicle screw placement, especially for training surgeons.