| Combining closely with the urgent need for computer-assisted technology of parallel external fixation for precise minimally invasive treatment of fracture reduction,this article takes a parallel external fixation as the research object and systematically develops computer-assisted software design,pose acquisition,interactive reduction trajectory planning,and etc.The main research achievements are as follows:1.Computer-assisted software development based on WebGL technology.First,analyze the process of the fracture reduction surgery and the existing computer-assisted softwares,refine the software requirements,divide the software into function modules,and propose the software development goals of reconstructing a 3D model from CT images to achieve interactive reduction trajectory planning.Second,determine the software architecture and design patterns.Considering the potential needs of remote diagnosis and treatment,the browser / server architecture is used as the basic architecture;in order to reduce the coupling of the system and improve the software efficiency,the model-view-controller design mode is selected.Construct a 3D interactive scene to reconstruct the fixation model.Compared with different Web3D technology,Three.js based on WebGL is chosen as the framework of 3D environment.Finally,combined with the software architecture,design patterns,and 3D interaction scenes,a digital computer-assisted software for parallel external fixation is constructed.It lays the foundation for pose acquisition and interactive reduction trajectory planning.2.The method of pose acquisition based on markers.First,the marker material is selected based on the 3D reconstruction effect of the CT image,and the structure and layout of the marker are designed.Secondly,the method of getting location information in the 3D environment is proposed.STL files are used to store 3D reconstruction model,and the STL file of markers is segmented with the region growth algorithm.The point cloud data of a single marker is extracted,and the spherical surface of the marker is determined by the least square method,and then the spherical center coordinate of the marker is got.Combining the geometric relationship between the marker and the parallel external fixation,the center position coordinates and transformation matrix of the reference ring and the moving ring of the fixation are solved to obtain the pose parameters.Finally,the coordinate system conversion and ray picking method is described.A comparative experiment of this method and the method with using X-ray is carried out.The method in this paper has good accuracy and solves the problems of interactive fracture reduction trajectory planning.3.Interactive trajectory planning method based on intact side-affected side control.First,starting from the symmetrical relationship of the lower limbs of a normal human body,a method of reduction by using 3D reconstruction model of intact side and affected side is proposed,and it forms a reduction trajectory including a starting point,a series of key points,and an end point.Secondly,design the human-computer interaction interface,realize the interactive operation of the 3D reconstruction model,and control the pose of the 3D reconstruction model.The inverse solution analysis of the parallel external fixation is performed to get the strut lengths.Spherical linear interpolation generates trajectories among the starting point,key process points,and end points.It solves the problem of uneven variation of the angular velocity.The prescription generation method of reduction trajectory is set.Finally,experiments are conducted to verify.The results show that fracture reduction is good.This paper designs computer-assisted software for parallel external fixation based on 3D interactive technology.It realizes visualization and digitization of fracture reduction treatment processes such as pose acquisition,reduction trajectory planning,and electronic prescription generation.It can reduce the burden of physicians in learning.It also provides theoretical basis and technical support for the development of accurate,efficient and reliable external fixation robot system. |
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