Navigation Technology Of Intramedullary Nail Distal Locking Surgery Based On Augmented Reality

Intramedullary nail fixation is the first choice for the treatment of femoral and tibial fractures,but the locking of the distal hole of intramedullary nail in clinical operation has caused great difficulties for doctors.Traditional lock-in surgery is often carried out under the fluoroscopy of X-ray machine,which will lead to a large dose of radiation exposure,and the effect of instructions given to surgeons is not intuitive,and the repeated fluoroscopy operation will also consume a lot of time.In this paper,the advantages and disadvantages of the existing auxiliary system are analyzed and studied.Combined with computer graphics,orthopaedic surgery medicine and augmented reality technology,a set of augmented reality orthopaedic operation platform is developed on the basis of mobile C-arm X-ray machine.At the same time,on the basis of the traditional operation process,the preoperative nail hole alignment algorithm and intraoperative drilling navigation scheme are developed to effectively assist the operation The doctor carried out the drilling and positioning operation.This paper first analyzes the X-ray and camera optical imaging model,demonstrates the theoretical basis of the virtual real fusion,and then proposes the normal coincidence registration method for the drilling operation requirements in the distal locking of intramedullary nail.According to the working principle of the system,the sliding camera frame and cross calibration target are designed,and the hardware of the system platform is built.The augmented reality system attached a camera to the C-arm machine to capture real-time images of real-time surgical scene,and used cross target calibration to obtain the transformation law of image fusion.It only needs to complete one calibration to achieve stable intraoperative virtual real image fusion.For the difficulty of cross target alignment under X-ray perspective,this paper proposes a video navigation aided registration method based on parallax.For the nail hole alignment process before drilling locking,this paper develops an auxiliary alignment method based on optical flow method and neural network.Firstly,the optical flow method is used to recognize the mark movement on the skin surface,and the movement displacement information is iterated into the calibrated fusion projection matrix.Then,the neural network is established to train the three-dimensional model of intramedullary nail.After the training,the shape of nail hole in X-ray fluoroscopy is identified,the deflection angle of intramedullary nail is predicted,and the rotation alignment is carried out.Finally,according to the motion freedom requirements,a leg fixture with accurate rotation angle is designed to assist doctors to achieve the nail hole alignment state according to the augmented reality image information.For the navigation of intraoperative drilling operation,this paper designs a positioning guide sleeve.The positioning attitude is determined by the way that two points on the drill axis coincide with the pin hole in the perspective view,and the direction of the drill is controlled not to shift in the process of drilling.In addition,a cross ratio fitting algorithm based on the least square method is developed for the error in the installation of the guide sleeve.Finally,in order to solve the noise in the calculation,Kalman filter is used to smooth the calculation results,so as to achieve stable navigation and positioning effect.Finally,in order to verify the effect of the augmented reality surgical navigation system,experiments on image fusion accuracy,nail hole alignment accuracy and bone model drilling were carried out.The average error of image fusion is 0.788 mm,the average error of nail hole plane alignment is 0.893 mm,the ratio of nail hole rotation angle prediction to meet the drilling requirements is 99%,the average time of bone mold drilling experiment is about 2:58,and the overall success rate of the drilling experiment was 85%.It basically proves the feasibility of the augmented reality surgical navigation system in clinical scenes,and has a good guidance effect on intraoperative surgical operations.