Robotic Guidance in Spinal Fusion

Dr. Hedequist looking at a model of the spine after spinal fusion surgery.
Dr. Daniel Hedequist and surgeons at the Pediatric Spine Department of Boston have used robotic guidance in more than 300 surgeries. (Photo: Michael Godale, Boston Children’s Center)

Accurate screw placement is a top priority in any spinal fusion surgery, and for good reason. Improperly placed screws are the number one cause of surgical complications and reoperations, according to the Scoliosis Research Association. Although the majority of misplaced screws (4-15 percent of all screws) have no clinically significant impact, the goal for many spinal centers is zero.

“If you want perfection, you look for ways to maintain 100 percent accuracy,” says Dr. Daniel Heddequist, director of the Department of Spine at Children’s Hospital Boston.

In 2019, Boston Children’s Hospital became one of the first pediatric spine centers to employ the Mazor X Stealth robotic guidance system. The system combines preoperative planning, robotic guidance and surgical navigation. Heddequist sees the use of guidance systems as an important step in the continuing evolution of technology that, if used carefully, will lead the field to greater precision and safety.

“For some patient anatomy, it’s easy to find a clear trajectory, but if the patient is small or has severe deformities, it can be much more difficult,” Heddequist said. say. “Robots cannot tell if a trajectory is easy or difficult. Thanks to preoperative planning and navigation, the path is set and the surgeon can drill with more confidence.”

Since introducing the guidance system into the operating room, four surgeons in the spine department have used the guidance system in more than 300 spinal fusion surgeries. During that time, Heddequist and his colleagues have closely monitored case outcomes, identified areas of potential error, and refined processes and technology to optimize safety. their observations are Pediatric Orthopedic Journal and numerous other publications provide valuable insights for spine centers using or considering robotic guidance.

Change your workflow to improve accuracy

Registration of the patient’s anatomy (matching the positions and angles of the vertebrae to the navigation software) is essential for the safety of robot guidance. Loss of registration can occur for various reasons. For this reason, the Boston Pediatric Surgeon double-checks alignment accuracy before drilling each pilot hole and before placing individual screws.

In a review of 88 robotic procedures between February 2021 and November 2021, missing registrations were detected and corrected in 6 of the first 35 procedures. Heddequist concluded that the placement of the screws could create enough torque to displace the adjacent vertebrae.

Upon identifying this potential problem, the team modified the surgical process to drill all pilot holes before placing the screws. Implementation of this procedure did not result in further loss of enrollment for her remaining 53 patients.

Technology to improve accuracy

One of the early concerns with robotic navigation systems was the slow speed of navigation drills and the potential for slippage on uneven or sloping surfaces. This problem, known as skiving, can distort the starting point, the angle of the drill path, or both.

Emerging Technologies: Surgical Headsets

Computer-assisted navigation gives surgeons a new level of visibility, but it also comes with trade-offs. In crowded operating areas, navigation screens are often placed sideways, forcing surgeons to look away from the operating area. Surgeons at Boston Children’s Hospital have started using headsets during freehand navigational surgery, allowing them to see both the patient and the navigation screen at the same time.

Early on, surgeons at Boston Children’s Hospital reduced the risk of skiving by flattening sloping and irregular surfaces before drilling. Doing so reduced the risk of slippage, but could interfere with alignment if the vertebrae were displaced in the process.

High-speed drills with navigation that cut directly through irregular surfaces eliminate the need to flatten the bone surface. Boston Children’s Center is the first pediatric center to use high-speed drills. Surgeons also ensure safety with the “tapping” method, where you can feel the drill moving down the pedicle and into the vertebral body.

Aiming for 100% Accuracy in Spinal Fusion

Shortly after the introduction of this guidance system, the Boston Pediatric Spine Division recruited other centers using the system to participate in a national registry of pediatric spine centers. Participating clinicians and researchers use the pooled outcome data to analyze the system’s long-term impact on accuracy, operative time, and radiation exposure.

“Technology will continue to play an important role in improving the precision of spinal fusion,” Heddequist said. “As an experienced center with a successful history of freehand operation, we are able to move the site forward without compromising safety.”

Learn more about the Spine Division here.

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