Minimally Invasive, Stereotactic, Wireless, Percutaneous Pedicle Screw Placement in the Lumbar Spine: Accuracy Rates With 182 Consecutive Screws

Background: Standard fluoroscopic navigation and stereotactic computed tomography-guided lumbar pedicle screw instrumentation traditionally relied on the placement of Kirshner wires (K-wires) to ensure accurate screw placement. The use of K-wires, however, is associated with a risk of morbidity due to potential ventral displacement into the retroperitoneum. We report our experience using a computer image-guided, wireless method for pedicle screw placement. We hypothesize that minimally invasive, wireless pedicle screw placement is as accurate and safe as the traditional technique using K-wires while decreasing operative time and avoiding potential complications associated with K-wires.

Methods: We conducted a retrospective review of 42 consecutive patients who underwent a stereotactic-guided, wireless lumbar pedicle screw placement. All screws were placed to provide fixation to a variety of interbody fusion constructs including anterior lumbar interbody fusion, lateral interbody fusion, and transforaminal lumbar interbody fusion. The procedures were performed using the O-arm intraoperative imaging system with StealthStation navigation (Medtronic, Memphis, TN) and Medtronic navigated instrumentation. After placing a percutaneous navigation frame into the posterior superior iliac spine or onto an adjacent spinous process, an intraoperative O-arm image was obtained to allow subsequent StealthStation navigation. Para-median incisions were selected to allow precise percutaneous access to the target pedicles. The pedicles were cannulated using either a stereotactic drill or a novel awl-tipped tap along with a low-speed/high-torque power driver. The initial trajectory into the pedicle was recorded on the Medtronic StealthStation prior to removal of the drill or awl-tap, creating a "virtual" K-wire rather than inserting an actual K-wire to allow subsequent tapping and screw insertion. Accurate screw placement is achieved by following the virtual path as an exact computer-aided design model of the screw traversing the pedicle is projected onto the display and by using audible and tactile feedback. A second O-arm scan was obtained to confirm accuracy of screw placement.

Results: A total of 20 women and 22 men (average age = 56 years) underwent a total of 182 pedicle screw placements using the stereotactic, wireless technique. The total breach rate was 9.9%, with a clinically significant breach rate of 0% (defined as >2 mm medial breach or >4 mm lateral breach) and a clinical complication rate of 0%.

Conclusions: Wireless, percutaneous placement of lumbar pedicle screws using computed tomography-guided stereotactic navigation is a safe, reproducible technique with very high accuracy rates.