Robotic-Assisted Pedicle Screw Placement During Spine Surgery

Abstract

Preoperative planning software and a robotic device facilitate the placement of pedicle screws, especially in patients with difficult anatomy, thereby increasing the feasibility, accuracy, and efficiency of the procedure. The robot functions as a semiactive surgical assistive device whose goal is not to substitute but to offer the surgeon a set of versatile tools that can broaden his or her ability to treat patients¹.

Description: The robotic guidance system consists of a bed-mounted surgical arm and a workstation. We used the Mazor X Stealth Edition Robotic Guidance System by Medtronic for spine surgery, which has been previously described^2-5. Unlike other systems that are navigation-based and require an optical tracking mechanism, this system relies on the preoperative plan to be referenced using the intraoperative registration. The workstation runs an interface software that facilitates preoperative planning, intraoperative image acquisition and registration, kinematic calculations, and real-time robot motion control. The robotic arm is mounted onto the bed as well as rigidly attached to the patient's spine. It can move in 6 degrees of freedom to provide the preplanned screw trajectory and entry point thereby allowing the surgeon to manually perform the drilling and screw insertion through either an open or percutaneous procedure by first seating a drill tube and then drilling and tapping the hole as needed.

Alternatives: Other robotic systems include the ROSA robot by Medtech, the ExcelsiusGPS robot by Globus Medical, and the SurgiBot and ALF-X Surgical Robotic systems (both from TransEnterix). The Da Vinci Surgical System (Intuitive Surgical) has been utilized for laparoscopic anterior lumbar interbody fusion (ALIF), but it has not been approved by the U.S. Food and Drug Administration for actual spinal instrumentation. Alternative surgical techniques for pedicle screw placement include the freehand fluoroscopy-guided technique and intraoperative image-assisted computer navigation techniques, including isocentric C-arm (Iso-C) 3D (3-dimensional) navigation (Siemens), computed tomography (CT) navigation, O-arm navigation (Medtronic), CT-magnetic resonance imaging co-registration technology, and a 3D-visual guidance technique^6-8.

Rationale: The robotic-guided pedicle screw placement offers the following benefits over conventional dorsal instrumentation techniques: improved accuracy and safety in pedicle screw insertion^2-4,9-13; precision in screw size selection and planned screw positioning²; a reduction in exposure to radiation for the surgeon, the patient, and the operating-room staff^{9,11,12,14-19}; simplicity and user-friendliness with a moderate learning curve^10,11,20,21; ease of registration and reduction of operating time²; significant enhancement of the surgeon's ergonomics and dexterity for repetitive tasks in pedicle screw placement^15,22-24; and a wider coverage in function to include utilization during minimally invasive surgery where applicable^11,25.

Expected outcomes: Accuracy rates between 94.5% and 99%, comparable with those in our study¹⁰, have been reported with the robotic-guided pedicle screw insertion technique, even in studies involving complex deformities and revision surgeries for congenital malformations, degenerative disorders, destructive tumors, and trauma^2-4,9-13. The safety of this technique, in terms of reduced complications and intraoperative radiation exposure, has also been documented as higher than that for freehand fluoroscopic guidance or other navigation techniques^{9,11,12,14-19}. The feasibility of this procedure has been further extended to minimally invasive procedures and to use in the cervical region, with replication of its advantages. It is associated with a reasonable learning curve, with consistent successful results after 25 to 30 patients.

Important tips: The principles of robotic-guided pedicle screw placement are similar irrespective of the system used.Although initially utilized mainly for thoracolumbar pedicle screw insertion, the latest robots and software have been adapted for use in the cervical spine with equivalent efficiency and accuracy.Robotic guidance can be employed in non-pedicle-screw-insertion procedures.Challenges include radiation exposure, trajectory failure, equipment and software failure, failed registration, logistics, time, and high cost.

Fig. 1

The Mazor X Stealth Robotic guidance system for spine surgery (Medtronic). (Image courtesy of Dr. Isador H. Lieberman.)

Figs. 2-A

Coronal and midsagittal views of the lumbar spine showing all the planned rods, screw trajectories, and measurements from L1 to L5.

Figs. 2-B

Axial view of L3 vertebral body at the level bisecting the planned screw trajectories along their length.

Figs. 2-C

Right-sided sagittal view showing the planned right screw trajectory completely within the right L3 pedicle.

Figs. 2-D

Transpedicular coronal view showing both the right and left screw trajectories completely within their respective pedicles at the L3 vertebral body level.

Fig. 3

Draping the surgical system and the surgeon’s screen with sterile sleeves.

Fig. 4

Making the anteroposterior radiograph with the reference frame strategically positioned over the segments to be instrumented for registration and referencing.

Fig. 5

Making the oblique radiograph with the reference frame strategically positioned over the segments to be instrumented for registration and referencing.

Fig. 6-A

Beginning the insertion of the drill tube cannula with the blunt trocar.

Fig. 6-B

Removing the trocar.

Fig. 7-A

Passing the second drill cannula, which is serrated at its end and with a narrower lumen, through the initial drill tube cannula.

Fig. 7B

The serrated second drill cannula with a narrower lumen is tapped into place to maintain its position and perform its function as the drill guide.

Fig. 8

Placing the drill into the guide and performing the drilling process in oscillation mode for the pilot hole.

Fig. 9-A

Passing a Kirschner wire through the exchange tube.

Fig. 9-B

Inserting the pedicle screw over the Kirshner wire after removing the working drill cannulas, the robotic arm, and exchange tube only out of the way.

Fig. 10

Robotic software image of fusion of the axial CT images of the preoperative planned screw trajectories and postoperative visualized screws. Blue (right) and yellow (left) markings indicate the planned trajectories, dashed black lines indicate the executed trajectory, and pink inscriptions indicate the deviation measurements from the planned preoperative trajectory. Pedicle screws shown are completely within the margins of the respective pedicles.