Factors causing deviation of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis: why does deviation still occur even with robotics?

Abstract

Purpose: To clarify the factors that are likely to cause deviation in robot-assisted pedicle screw placement in surgery for adolescent idiopathic scoliosis (AIS).

Methods: Thirty-two consecutive patients with AIS who underwent posterior spinal fusion using a spine robotics system were included. Robot-assisted pedicle screw placements were evaluated using Gertzbein-Robbins system. Deviation rates for breaches of 2 mm or more (Grade C, D, and E) were calculated. Pedicle channel grade, vertebral level, distance from the reference frame (RF), insertion order of the screws, curve laterality, and use of a navigated high-speed drill were investigated as factors causing deviation.

Results: A total of 465 robot-assisted pedicle screws were placed, and deviations were observed in 13 (2.8%). The deviation rates were significantly different by pedicle channel grade (Grade 1: 0%, Grade 2: 0%, Grade 3: 3.1%, Grade 4: 20.4%, p < 0.001), vertebral level, and use of a high-speed drill. There were no significant differences in deviation rates for distance from the RF, insertion order of the screws, or curve laterality. Logistic regression analysis showed pedicle channel grade 4 was a significant risk factor for deviation.

Conclusion: The factor that was most likely to cause deviation in robot-assisted pedicle screw placement in AIS was pedicle channel grade. The most likely situation to cause deviation was a narrow pedicle with an internal diameter of less than one mm. Surgeons should be aware that even with the use of robotics, placing screws into such narrow pedicles is challenging.

Keywords: Adolescent idiopathic scoliosis; Pedicle channel; Pedicle screw; Robotic-assisted pedicle screw placement; Robotics.