Electromagnetic navigation for percutaneous guide-wire insertion: accuracy and efficiency compared to conventional fluoroscopic guidance.

The combination of electromagnetic (EM) navigation with intraoperative fluoroscopic images has the potential to create the ideal environment for spinal surgical applications. This technology enhances standard intraoperative fluoroscopic information for localization of the pedicle entry point and trajectory and may be an effective alternative to other image-guided surgery (IGS) systems. This study was performed to assess the accuracy and time efficiency (placement and fluoroscopy) using EM navigation versus conventional fluoroscopy in the placement of pedicle guide-wires. Kirschner wire (K-wire) placement was performed in cadavers from T8 to S1 using EM navigation versus conventional fluoroscopy. Time for set-up, placement, and fluoroscopy was recorded. After insertion, the accuracy for each level was assessed for the presence and location of facet joint, pedicle, or vertebral cortical perforation using computed tomography imaging with multiplanar reconstructions. K-wire placements were 100% successful for both methods. Comparing EM-based IGS-assisted placement with the conventional fluoroscopy method showed a longer set-up time of 9.6 min versus 3.6 min, respectively. However, mean placement times of 6.3 min versus 9.7 min (P=0.005) and mean fluoroscopy times of 11 s versus 48 s (P<0.0001) were both shorter for the EM group. There were no significant differences in the proportion of pedicle, vertebral body, or facet joint breaches. A higher proportion of ideal trajectories was achieved in the EM group. Therefore, we have shown that an EM IGS system can assist the spine surgeon in minimally invasive pedicle screw insertion by providing high-accuracy K-wire placement with a significant reduction in fluoroscopy time.

Electromagnetic field-based image-guided spine surgery part two: results of a cadaveric study evaluating thoracic pedicle screw placement.

STUDY DESIGN: Human cadaveric. OBJECTIVES: Compare the accuracy of electromagnetic field (EMF)-based image-guided thoracic pedicle screw insertion to conventional techniques using anatomic landmarks and fluoroscopy. BACKGROUND: Image-guided surgical systems that aid in spinal instrumentation seek to minimize radiation exposure and improve accuracy. EMF image guidance was developed as an alternative to optical tracking to eliminate potential line of sight issues. MATERIALS AND METHODS: Four fresh-frozen human cadavers were randomly allocated into two groups. Pedicle screws were inserted from T1 to T12 using anatomic landmarks and fluoroscopy in group 1 and image guidance in group 2. Insertion and fluoroscopy time were recorded. Anatomic dissections were performed to assess screw placement. RESULTS: Image guidance placed 92% of thoracic pedicle screws safely, and conventional fluoroscopy placed 90% safely. The average degree of perforation was 2.4 mm with conventional fluoroscopy and 1.7 mm with image guidance (P = 0.055). Fluoroscopic time per screw was 5.9 seconds for conventional fluoroscopy and 3.6 seconds for image guidance (P = 0.045). Insertion time per screw was 4.35 minutes for conventional fluoroscopy and 2.98 minutes for image guidance (P = 0.007). However, when set-up time and image capture time were taken into account, the total insertion time per screw was not significantly different between the two groups. CONCLUSIONS: Our study has shown that EMF image-guided thoracic pedicle screw placement results in a similar incidence of safely placed screws as does conventional fluoroscopy. When set-up time and image-capture time were factored in for image guidance, the average time to insert a pedicle screw was equal for both techniques. The use of EMF image guidance significantly reduced fluoroscopic time and thus radiation exposure per screw compared with conventional fluoroscopic techniques.

Minimally Invasive Direct Access Surgical Technology - MIDAST(TM).

The minimally invasive direct access surgical technology (MIDAST) has grown out of previous experience applied in otolaryngology and endoscopic microsurgery. From the time of Ambroise Pare and for centuries surgeons have made large incisions to gain adequate access for manipulation with large, straight, bulky instruments and achieved adequate illumination by the sun and later by artificial lighting.