Augmented Reality-based Research Provides Surgeons With The Most Comfortable Surgery

Total hip arthroplasty mainly treats severe wear and collapse of the hip area,and it has been proven to be an effective way for end-stage hip joint damage.The difficulty of the surgery is how to accurately implant the prosthesis,which is a key factor in determining the success or failure of the surgery.If the implantation position of the acetabular cup prosthesis does not match the acetabular cavity,it is easy to cause loosening and dislocation of the artificial joint after surgery.This thesis focuses on how to achieve the precise implantation of the acetabular prosthesis based on advanced technology to optimize the surgeon’s operation.The main research elements are as follows.（1）For preoperative planning,this thesis adopts a CT/MRI image segmentation and 3D reconstruction method,which has the advantages of good image segmentation effect and fast calculation speed.Based on the guidance from the clinical partner,we obtained the reference point positions of the bone landmarks and acetabular cup-hole in the virtual model under the point cloud based on the features of the bone landmarks and the spherical fitting algorithm,respectively.In addition,we calculated the optimal path for acetabular cup implantation based on the information provided by the clinical partner on the anteversion and abduction angles.（2）To address the problem of positioning the instrument and model datum points during surgery,this thesis uses a computer vision tracking technique,which consists of four parts:camera calibration,binocular stereo ranging,binocular tracking,and virtual object and real space alignment.Camera calibration establishes the transformation relationship between the pixel coordinate system in the binocular stereo camera field of view and the world coordinate system in the real scene.To accurately measure depth information,we use binocular stereo ranging,which consists of four parts: binocular calibration,corner point detection,feature matching,and stereo ranging.Based on the consideration of computational complexity,operation speed and accuracy,we used the classical Harris algorithm and the feature matching algorithm of NCC fast similarity to complete the corner point detection and feature matching.In terms of tracking algorithm selection,we choose the marker recognition tracking method with high intelligence,high accuracy,low latency and secondary tracking characteristics.Meanwhile,the virtual objects are aligned to the real scene based on the markers.In the experiments comparing the positions of the bone landmarks in the virtual and real spaces,the average errors of alignment in position and orientation were found to be 2.2 mm and 0.8°,which illustrates the feasibility of the augmented reality navigation framework proposed in this thesis in total hip arthroplasty.（3）To address the problem that the surgeon’s surgical operation under computer vision is not as convenient as unaided operation,a master-slave virtual simulation training system for acetabular cup positioning was developed in this thesis.This system can provide a safe and realistic training environment for physicians,thus alleviating the pressure on limited medical resources.The master-slave virtual simulation training system is mainly composed of two parts: master-slave control module and virtual scene simulation module.The master-slave control module is mainly responsible for the command interaction between the input and the controller? the virtual scene simulation module mainly includes the design of the virtual skeleton model and the 3D reconstruction of the virtual surgical environment,as well as the simulation of the surgical tools.During the training process,the surgeon completes the mapping of the virtual surgical tool in the controller through the physical master hand.When the virtual surgical tool reaches the reference point of the acetabulum with the correct posture,the interaction mechanism on the virtual training interface will prompt the user to operate correctly.In the experiment,five users experienced the feasibility of the system,and the time spent through the trial showed that the system significantly improved proficiency.（4）To address the problem of low accuracy of freehand positioning during surgery,a master-slave controlled mechanical platform for total hip replacement was designed in this thesis.The main frame of the mechanical platform consists of a Hbot motor synchronous belt XY-axis drive structure,a stereo camera fixation slot,a Z-axis drive device and a robotic arm end-effector.In this thesis,we design and build the mechanical platform based on SolidWorks,based on stepper motor,special driver and switching power supply for electrical energy conversion or transmission,and embedded microcontroller development board STM32F4 for connection and control.In the stepper motor control system,we complete the control of the stepper electric motion by input pulse width modulation（pulse width modulation,PWM for short）.The standard deviations of the mechanical stage in x,y and z directions were measured to be 0.35 mm,0.16 mm and 0.45 mm in turn,which significantly improved the positioning accuracy of the surgery.