A Study on Resistive Force and Torque Feedback from Muscles and Tissue in Spine Surgical Robots for Improved Precision and Control

Minimally invasive spinal surgery (MISS) faces significant challenges due to unknown resistance forces from muscles and tissues, adversely affecting screw fixation accuracy. This study characterizes force and torque responses to improve spinal surgical robot control and precision. The proposed system employs a newly designed instrument tip with a 6 -axis force/torque sensor and cylindrical guidance sleeve, aligned with the spinal screw insertion point. Experiments used a multilayered lumbar spine phantom fabricated from biomimetic silicone replicating muscle and soft tissue properties. Raw data underwent gravity compensation and signal filtering for stability and accuracy. Results show the phantom effectively reproduces tissue elasticity, with peak resistance forces varying by position and direction (left L1: Roll 15.67 N, Pitch 15.32 N). Forces and torques exhibited linear relationships with inclination angle and insertion depth, where small angular deviations at greater depths induce excessive resistance. Stiffer silicone phantoms produced higher resistance forces. These findings highlight the necessity for adaptive robotic control strategies accommodating patient-specific biomechanical variations, providing foundation for force/torque compensation algorithms and optimized robotic motion planning to enhance MISS precision, safety, and stability.