Registration of Robot for Robot-Assisted Spine Surgery: A Comprehensive Guide

Robot-assisted spine surgery has revolutionized the field of minimally invasive spine and neuro procedures. One of the most critical steps in these surgeries is the registration of the robot, ensuring precision, safety, and efficiency. This guide outlines the essential steps and best practices for robot registration, drawing insights from clinical experiences and advanced techniques.

Step 1: Robot Setup

1.1 Verifying the Arm Functionality

Before initiating surgery, the robot’s arm must undergo an automated functionality check. The robotic system tests the arm’s full range of motion, including compound movements, to ensure accurate operation. The surgeon verifies the accuracy manually at the end of this process.

1.2 Accuracy Verification

The accuracy verification tool is inserted through the arm guide. This tool should fit into the divot without touching the sides, confirming alignment. Manual confirmation completes this step.

Step 2: Surgical Field Preparation

2.1 Conventional Draping

Draping is essential to maintain sterility. The conventional method involves:

• Draping the robot after scrubbing and painting the surgical field.

• Adding an additional sterile sheet to cover the lower body of the patient.

  
  

2.2 Delayed Draping

If the robot is used in another operating room, delayed draping can maintain sterility. The robot is draped in its launched position without mounting it on the table.

Step 3: Patient Mounting

3.1 Mounting Options

Robotic systems require stable mounting of the patient’s anatomy. Methods include:

• Spinous Process Clamps: These attach to the spinous process from T1 to S2 but are less preferred due to their bulkiness and obstructive design.

  

  

• Schanz Pins: Commonly used in lumbar fusions, these pins provide versatile mounting options.

  

• They can be placed:

  

  • In the PSIS (Posterior Superior Iliac Spine) for instrumentation from S2 to L2.

  • In the pedicle for thoracic instrumentation.

    

  • While placing it in the PSIS one must be careful as sometimes it may come in the way of the S2 alar iliac screw trajectory as shown in video.

  
  
  
  

  • In such cases that screw is placed last and with minimal movement of the patient.

  • All surgeons and OT techs using the robot must be familiar with the emergency stop button both on the robotic arm and on the workstation.

  • Closed loop communication between the OT technician and the surgeon is necessary to prevent inadvertently sending the robotic arm with instruments still in the arm guide.

3.2 No Physical Mounting

In some cases, such as kyphoplasty or cervical/thoracic procedures, physical mounting is unnecessary. With careful use of power tools and minimal force on the robotic arm, the patient’s anatomy remains stable without mounting.

3.3 Arm Stretch Test

The arm is brought into the full stretch position and depending on the upper instrumented vertebra, the shoulder is adjusted.

If further adjustment is required, the robot can slide cranially or caudally.

3.4 Software Mount

After physically mounting the robot, the software mounting is done by the click of a button on the workstation.

This locks all further manual movement of the shoulder, therefore it is important to ensure the cranial most trajectory can be achieved prior to this.

Step 4: 3Define Scan

The 3Define scan maps the surgical field using two infrared and one optical camera. The robotic arm scans the field in a 180-degree arc to identify obstacles and define “No-fly-zones.” Key considerations include:

• Turn off overhead lights and cover reflective surfaces.

• Avoid inadvertent scanning of surgeons’ or nurses’ hands, which could disrupt the robot’s trajectory.

• Verify navigated instruments during the scan by placing their tips in the robot’s reference array.

Step 5: Snapshot and Accuracy Checks

5.1 Snapshot Registration

The robot moves to a predefined position, and a snapshot tracker with fiducials determines its location relative to the reference frame. Issues like improper placement of fiducials or obstructions must be addressed promptly.

5.2 Re-snapshot and Accuracy Restoration

If navigation accuracy is lost, the snapshot process is repeated. The blunt passive planar probe is used to verify accuracy on known bony landmarks. If issues persist,

rescanning is necessary.

Step 6: Fiducial Arrays and Fluoroscopy Registration

6.1 Fiducial Arrays

• Intraoperative CT arrays have 4 beads, while CT-fluoro arrays have 52 beads.

• The array is attached to the robotic arm via an extender, ensuring clear visualization of the target vertebrae.

  
  

6.2 Fluoroscopy Registration

AP View

Oblique View

• Acquire AP and oblique images of the target vertebrae using the fiducial array.

• Ensure adequacy of images and verify them using the robotic system.

Step 7: Region of Interest and Scan Planning

7.1 Marking the Target Vertebrae

Using a blunt passive planar probe, mark the center of the target vertebra. The fiducial array should be positioned as close to the patient’s anatomy as possible without contact.

7.2 Maximizing Vertebrae in CT-Fluoro

Fine-tune the robotic arm to optimize the inclusion of multiple vertebrae in a single scan.

The Fiducial Marker should be brought as close to the patient's body as possible.

Step 8: Unmounting the Robot

After placing and verifying all screws, the robot is returned to its storage state. The manipulator is disconnected, and the system is unmounted from the bed frame adapter, completing the procedure.