Research On The Risk Control Of Implant Channel Drilling In Robot Minimally Invasive Cochlear Implantation

Background: cochlear implantation is the best method for the treatment of very severe sensorineural hearing loss.The development of surgical robot promotes the innovation of this method.Traditional cochlear implantation has many clinical problems,such as large surgical trauma,narrow vision,residual hearing loss and poor consistency of surgical results.Robot assisted cochlear implantation can enhance or even surpass the doctor’s perception,operation and control ability,which can solve these clinical problems.Due to the risk of damage to the important surrounding structures(facial nerve,chorda tympani nerve,ossicular chain,etc.)in the process of minimally invasive drilling,the main risk of damage is mechanical damage and thermal damage to the surrounding structures.Reasonable mechanical and temperature parameters of mastoid drilling channel are the prerequisite for robotic cochlear implantation.At present,there are few researches on the mechanical parameters and temperature of robot mastoid drilling channel.This study explores the mechanical and temperature parameters of mastoid drilling channel in robot cochlear implantation,establishes a damage model based on finite element analysis,and verifies the accuracy of the model through experiments,so as to provide theoretical basis for the safe approach of robot cochlear implantation.Objective: To study the risk factors of cochlear implant channel drilling in robotic minimally invasive cochlear implantation,and to provide mechanical and temperature control parameters for the development of minimally invasive cochlear implant robot.Methods:(1)temporal bone samples were collected and scanned by CT.Based on the CT scanning data of two adult male human temporal bone specimens,the finite element simulation model of human temporal bone was established.The simulation model of mastoid drilling process was further carried out,and the mechanical and temperature distribution maps during drilling process were calculated and analyzed.(2)Through the experiment of facial nerve thermal injury in rabbits,the threshold of nerve thermal injury was obtained;and the mechanical and temperature parameters were obtained through the simulation model of mastoid drilling channel,and the optimal drilling parameter combination within the temperature threshold was analyzed.(3)The force and temperature in the drilling process are detected by navigation and positioning,NC machine tool drilling,mechanical sensor and infrared thermal imager.The average gray value of the drilling channel is extracted by the three-dimensional reconstruction software mimics,and compared with the mechanical parameters.The accuracy of the mechanical and temperature parameters of the finite element model of mastoid drilling channel is verified by experiments.Results:(1)the finite element model of human temporal bone and the simulation model of mastoid drilling process were established,and the mechanical and temperature distribution maps of drilling process were obtained.(2)The amplitude of evoked potential increased slightly at 37-42 ℃,and all facial nerve evoked potentials disappeared at 58 ℃,and the latency of evoked potential was gradually prolonged when it exceeded 45 ℃,and the thermal injury threshold of facial nerve was obtained.according to the mechanics and temperature distribution of mastoid drilling channel,the mechanical parameters and temperature parameters were obtained.(3)After drilling,the ratio of temperature drop and maximum temperature is linear regression,and the goodness of fit is close to 1.It is found that the force is related to the gray value of CT.The larger the CT value is,the greater the force may be produced.It is found that the feed speed has a great influence on the temperature rise,and the temperature rise range of 90 mm / min is less than 30 mm / min and 60 mm / min.Compared with the experimental and simulation results,the accuracy of the finite element model of mastoid drilling channel was verified.Conclusion: the drilling mechanics and temperature parameters based on the finite element model analysis can provide a theoretical basis for the safety of mastoid drilling in robotic cochlear implantation.