Research On Spinal Biomechanical Modeling And Robot Motion Compensation In Clinical Dynamic Environment

Pedicle screw fixation is a surgical method for the treatment of common spinal diseases such as lumbar fractures,scoliosis and spinal stenosis.However,due to the complex structure of the spine,fine operation and long time,the difficulty of spinal surgery is greatly increased.Therefore,the research on the use of robots to assist doctors in performing surgery has become more widespread.However,due to the operation of the surgical instrument on the spine during the operation and the breathing movement of the patient itself,the position of the spine will change,which will affect the accuracy and safety of the operation.In this paper,based on the changes of the position of the spine caused by the influence of surgical instrument force and respiratory motion in spinal surgery,a predictive model of the position of the spine is established based on the mechanics theory,and the reasonable motion compensation scheme is designed.In this paper,a modeling method for the deformation of the spine based on the elastic mechanics method is proposed for the deformation of the spine by the action of the surgical instrument.The real lumbar data is collected to reconstruct the three-dimensional model of the lumbar spine.At the same time,the finite element simulation of the three-dimensional lumbar vertebrae model is carried out,and the mathematical model is verified and the parameters are estimated by the data obtained by the simulation.In order to get the relationship between respiratory movement and spinal movement,by analyzing the movement of the thoracic cavity and the structure of the spine during respiration,the movement model of the physiological respiration of the spine is established.And a physiological signal acquisition system is built based on the infrared tracking device and the Arduino development board.The data of displacement,tidal volume and pressure changes are collected under the condition of calm respiration.And the mathematical model of respiratory motion is estimated by the measured data.In order to verify the feasibility of the mathematical model of deformation which caused by lumbar force,the position-based control system is built by combining PID and impedance control algorithm.The control system is simulated by the Simulink module and the results show that the model can compensate the deformation of lumbar spine which caused by the force of surgical instruments.In a real spinal surgery environment,the movement of the lumbar spine during surgery is affected by the action of the surgical instrument and the respiratory motion.The six degree of freedom motion platform is used to simulate the spinal respiratory movement during the operation,and the pig plate bone is fixed on the exercise platform with a clamping device,while the UR5 manipulator is used to drill holes on the pig bone.By comparing the drilling forces under the condition of ideal conditions(bone static),without compensation(bone movement,robot doesn't compensate for the motion),with active compensation(bone movement,robot compensates for the motion)and on the basis of active compensation,the deformation of spine caused by force is compensated at the same time(bone movement,robot compensates for the motion and the displacement caused by force deformation of spine),the data of drilling forces are analyzed statistically.The results show that the method of robot active compensation can well offset the influence of spinal respiratory movement on spinal surgery.It also verifies the simultaneous compensation of the deformation and respiratory movement of the spine,the force of surgical instrument is more stable and helps to improve the safety of the surgery.