“What exact variables contribute to accuracy of robot-assisted screw placement?” mused a team of researchers from the U.S. and Italy. Their work, “Factors Affecting the Accuracy of Pedicle Screw Placement in Robot-Assisted Surgery: A Multicenter Study,” was published in the December 1, 2022, edition of Spine.
Nader Toossi, M.D. is with the Musculoskeletal Education and Research Center in Audubon, Pennsylvania, and explained the background of the study to OTW, “Robotic-assisted spine surgery is on the rise, and so are questions regarding the accuracy of pedicle screw placement with the Excelsius GPS. At the time of this study, there was no multicenter published research on the factors that could affect the accuracy of pedicle screw placement with Excelsius GPS. We decided to design and conduct this study to uncover answers to some of the questions being asked by spine surgeons.”
Using radiographic and clinical data from three centers, the authors looked at offsets between the placed and preoperatively planned screws’ tips, tails (entry points), and angular trajectories. Later, the researchers digitally overlaid the preoperatively planned trajectories for the pedicle screws on the postop CT images of the placed screws. They then calculated the offsets between the tip, tail, and trajectory angulations were then calculated for each screw. In addition, accuracy of the placed screws was graded and reported according to the Gertzbein-Robbins grading system (grade A if there was no breach of the pedicle walls, B if there was <2 mm, C if there was <4 mm, D if there was <6 mm, and E if there was more than 6 mm of pedicle wall breach).
The team found that the overall contribution of the variables considered to the accuracy variation was 18%. The authors found that obesity, long constructs, female gender, surgeon, and vertebral levels were some of the factors that made small contributions to the different screw offsets.
Dr. Toossi commented to OTW, “The accuracy of screws placed with robotic assistance, as graded by the Gertzbein-Robbins grading system or measured offsets between planned and placed screw trajectories, is minimally affected by different patient- or screw-related variables.”
“We were surprised to find that some variables individually had statistically significant associations with the accuracy of screw placement. However, these variables, regardless of their significant association with the accuracy of placed screws, had little contribution to overall variability of accuracy itself. Overall, the robotic navigation technology was designed to increase accuracy and consistency in trajectory alignment for pedicle screw placement across different patient factors.”
“The current results were obtained from a retrospective, three-center study. In the future, we would like to execute prospective studies with more participating centers, to help us better identify the significant factors and their associated effects.”
