| [Background] In the recent years, the total hip arthroplasty (THA) as the efficient treatment has been broadly applied in the clinical field, however there is no universal criteria for the position of the acetabular cup input. The acetabular cup position is vital factors in the effects of the THR. it will d directly affects the longevity of the cup prosthesis. The postoperative lossening ,prosthesis impingement,pian,wearout, is closely connected with the cup position. How to avoid these negative factors will be a challenge faced by the clinical surgeons. Through coumputer assisted finite element analysis, we can understand the load distribution on any region of the reconstructed models. As the devolpement of the computer software program, it will be feasible for any researchers to use it to analyze the complicated biomechanmic problem and carry ou the tedious calculation process. the CAD/CAM assisted custom designi s a promising way because he life expectancy of prostheses will be highly improved and the loosing of the prostheses will be effectively avoided. [Objective] Based on the CT scan, the pelvic modedl was reconstructed. the abduction angle of the cup ranges from 30°~70°, and anteversion is from 5°~30°. On the Solideworks calculation platform, the cup was input to to acetabular in each position every 5°. The biomechanic analysis of the effects to the load distribution aroud the acetabular form tne different cup position was to carry out, in order to find out which position is good to the load distribution and define the safe range of the acetabular cup .therefore lay a theoretical foundation for the clinical work. Also, the pelvic reconstructed model was found through the the accuracy of the existed CAD program. The obtain pelvic model will give a beeter understanding to the load transmition on the pelvic. And it will also throw a light to the custom made pelvic for the large pevilc bone defficiency patients, which will improve the life quality of those patients. [Material and method] 1. The three-dimensional reconstruction of the pelvic 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 semi-automatic 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. (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 cup 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 the cup prostheses model was automatically performed through the Solidworks 2001. 3. The computer simulative comparison biomechanicalExperiment of the influence on the load distribution around the acetabular form different position of the none-cement acetabular components 3.1 the limitation analysis of the pelvic model. 3.2 The computer simulative comparison biomechanicalExperiment of the influence on the load distribution around the acetabular form different position of the none-cement acetabular components was carried out and the interface Mises load distribution,shear load were measured under the one-foot astand condition. [Result] 1. The reconstructed pelvic midel is helpful to understanf the transmition of load on the pelvic. it also provides the refrences for the custom made pelvic research.the pelvic finite element analysis is proved feasible by present study. 2. The major load didtribution area is around the post-superior region in the acetabular. 3. A consistent decress in contact area with increasing acetabular abduction...
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