Fluoroscopic Guided Targeting System with a Robotic Arm for Pedicle Screw Insertion

Introduction:

Simultaneous AP and lateral fluoroscopic images linked to a computer driven electromechanical arm (Robot) is being developed as a targeting system for pedicle screw insertion. This robotic arm is a precise motor–driven positioning system, which has 5 degrees of freedom (x, y, z, rot x, rot y) and securely aligns the surgical instruments to the exact entry site and trajectory. This technology enhances standard intra–operative fluoroscopic information to localize pedicle entry point and trajectory and may be an effective alternative to CT based image guided system (IGS) in pedicle screw placement. A pre–clinical study to assess the accuracy, time and cost–effectiveness of this system against conventional IGS was conducted.

Methods:

Pedicle screw placement was performed in 6 cadavers from T1 to S1 using IGS (Viewpoint, Picker International, Inc) on one side versus fluoroscopic targeting system (FGS, Z–KAT, Inc) on the other. A total of 208 from possible 216 pedicles were instrumented as 8 pedicle diameters were too small or not adequately imaged. Post–insertion, each pedicle was assessed for presence and location of cortical perforation by CT scan and direct visual inspection.

Results:

The number of successful screw placements were 89/102 (87.3%) for IGS and 87/106 (82.1%) for FGS. The success rates in the region of T9 to L5 for each system was nearly identical at 98.1% (53/54 for FGS, 51/52 for IGS). The mean time to register and operate on one level using the FGS was 14:34 minutes compared to 6:50 minutes using the IGS. The average fluoroscope time was 4.6 seconds per pedicle.

Discussion and Conclusions:

Our data indicates that this first–generation fluoroscopic targeting system can significantly assist the surgeon in pedicle screw placement. The overall accuracy compared favorably to a conventional IGS system. This system was particularly effective from T9 to L5. The fluoroscope time is also significantly reduced when compared to traditional methods, thus minimizing x–ray exposure to the patient and the operating room staff. Second–generation system, currently being developed with faster end–effector and user–friendly interface will significantly reduce the operation time as well as the fluoroscope time.