Development And Clinical Practice Of Three Dimensional Reconstruction And Morphological Analysis Of Hip Joint Software System

In hip replacement surgery,good anatomic match between prosthesis and a natomic host bone will improve long-term stability of joint implant.Computer-aided hip surgery planning and implant design applications require accurate three-dimensional(3D)hip joint models from CT slices.In this paper,we designed and developed a three dimensional reconstruction and morphological analysis of hip joint software system.We proposed an accurate and automatic segmentation method for the femoral head and acetabulum from CT slices.Then the 3D mesh model was constructed from the segmentation result.Finally,Morphological analysis was applied based on the 3D models.The software system is designed to achieve automatic segmentation algorithm based on hip joint sequence CT images.The outline of the femur was segmented and extracted by contrast enhancement,thresholding algorithm and region growth algorithm.The boundaries of the bone regions are further refined based on Bayes decision rule.Finally,3D model was constructed using Marching Cubes(MC)algorithm.The results show that the proximal femur of hip can be segmented and modelled fast and accurately with automatic segmentation algorithm.Moreover,this software system extracts femur 3D point cloud data from 3D mesh models and implements morphological analysis on femur: 1.Preliminary fitting was applied to femur point cloud using quadric surface fitting method.2.The surface invariant properties were used to determine the concrete type,center and main direction of surface.3.Then these properties were used to reconstruct surface of sphere model,ellipsoid model and rotational ellipsoid model and compare the fitting errors.4.Make analysis on fitting results.By morphological analysis on femur CT data of 21 volunteers(Male 7,Female 14)we found that 1)The anatomical morphology of femur is more likely to be rotational ellipsoid surface(p-value <0.01)and the fitting errors of rotational ellipsoid model and ellipsoid model were obviously smaller than the fitting errors of sphere model.The fitting errors of ellipsoid model and rotational ellip soid model were nearly the same.2)Morphological parameters of male are apparently larger than female.3)By statistical analysis on femur fitting results of rotational ellipsoid model we find that the hip joint ellipsoid rate is inversely proportional to age(P-value 0.009).That is femur is more likely to be a sphere surface as age decrease.The experimental results indicate that for artificial hip implant design,age and sex are main factors that should be considered and morphological design of prosthesis should be different for the young and the old.