| [Background] In the recent years, the total hip arthroplasty (THA) as the efficient treatment has been broadly applied in the clinical field, however the match degree of prosthesis shape to the femoral medullar cavity will directly affect the longevity of the prosthesis. Prolong the longevity is the key to prostheses design. Due to the diversity in different persons femoral shape, the common commercial prostheses can't meet need of match degree, therefore the stability of the prostheses cannot be guaranteed as the time passes. Through the CAD/CAM assisted custom design, the life expectancy of prostheses will be highly improved and the loosing of the prostheses will be effectively avoided. [Objective] Further modified the existed two sets of software and made CAD design through them. As the three-dimensional model of the prosthesis was founded, we used Solidwork software to build three-dimensional cement prosthesis and biological prosthesis model. Compared and analyzed the biomechanical characters of these three different models on the Solidwork platform to verified the accuracy of the existed CAD program and whether the custom designed prosthesis is superior to the other ones, Therefore laid a foundation to the research of CAM designed prostheses. [Material and method] 1. The three-dimensional reconstruction of the femoral prosthesis 1.1 The obtain of the CT images GEspeedlight 16CT scanned one fresh adult cadaver femoral from the proximal to distal part. There was 1.25mm between each scanned slice and the two-dimensional images of each slice were obtained. All the obtained data were put into the computer workstation for the later use. 1.2 The process of the obtained CT images The two-dimensional images of each slice in the workstation were conversed into the compact disc files and recorded on 700M CD-R. Through the calculation, we directly gained the CT images and using own developed CAD software carried on later experiments. 1.3 The edge detective Use Canny edge detective system to detect the images' edges. (1)Figured out the average coordinate value of all the detective edge points, namely the middle point in the three-dimensional space. (2)Took the middle point as the crossing point in the coordinate, the transverse line as the X-axis and the vertical as the Y-axis. Calculated the distance between each point and the crossing point. The angles (counter-clockwise) existing in them were also calculated. (3)Confirmed the two beginning point. one is in the outer contour, the other is in the inner contour. (4)Drew the contour according to the angle. 1.4 The modifying calculation of the custom femoral prosthesis Femoral stem prosthesis was drawn through the reconstructed femoral medullar cavity base on the engineering calculation formula. The cutting process was performed in every drawing out. The same process was repeat until we attained a prosthesis that provided an optimal implant-bone and also surgically insertable. 1.5 The conversion of two-dimensional images to three- dimensional one The originally obtained two-dimensional data were transformed into three-dimensional picture in order to make the picture more real for observation. 2. the three-dimensional reconstruction of cement and biological femoral prostheses 2.1 The CLY single-arm three-dimensional measurement device (made in China measurement technical institution) was used in measuring the cement and biological femoral prostheses. All measure data were put into the same coordinate. 2.2 The three-dimensional reconstruction of cement and biological femoral prostheses model was automatically performed through the Solidworks 2001. 3. The simulate comparison biomechanical experiment of cu stom designed femoral stem and cement,biological ones. 3.1 the limitation analysis of these prostheses. 3.2 The simulate comparison biomechanical experiment of custom designed femoral stem and cement ,biological ones. In the computer...
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