Design Of The Medial Pivot Knee Of Chese And Its Related Kinematics Analysis

PART ONE Design of femoral component based on study on Morphometrical measurements of resected surface and lateral rotated degree of femur of ChineseObjective:To Design of femoral component based on study on morphometrical measurements of resected surface and external rotation degree of femur of Chinese.Methods:Review the literatures about the morphometrical measurements of resected surface and external rotation degree of femur of Chinese. Using software Imageware (Unigraphics solutions, USA),the femoral component was designed in the prime type of a dual-radius knee system, based on Chinese anatomical characteristics.Results: Chinese femoral aspect rate(medial-lateral width/ anterior-posterior length) is larger than that of the Western people. We enlarge medial-lateral width 1.207 times. Femoral external rotation degree is 5°in Chinese, so we increase the external rotation degree by thickening lateral femoral posterior condyle.Conclusion: Medial-lateral width was enlarged 1.207 times and lateral femoral posterior condyle was thickened by build-in. Part Two Design of tibial component based on study on Morphometrical measurements of resected surface of tibia of ChineseObjective : To Design tibial component based on study on morphometrical measurements of resected surface of tibia of Chinese and the mechanical properties of tibial component fixation.Methods:Review the literatures about the morphometrical measurements of resected surface of tibia of Chinese, and the mechanical properties of tibial component fixation.Using software Imageware (Unigraphics solutions, USA), the tibial component was designed in the prime type based on Chinese anatomical characteristics, and the mechanical properties of tibial component fixation to ensure good stability and provide a homogeneous loading distribution.Results:The AP/ML ratio of proximal tibial resected surface of Chinese population was larger than those of several commonly imported tibial baseplates of total knee prosthesis. The cylindrical stem produces heterogeneous BMD changes under the tibial platform in knee arthroplasties, and this could be a potential risk factor for asymmetrical subsidence of this component, and large decrease in the medial region.however, the cruciform stem allows a more uniform loading distribution, resulting in a more homogeneous BMD decrease in the three analysed ROIs.Conclusion:The tibial component was enlarge the anteroposterior dimension 1.07 times, and the stem of the cruciform stem was added a new flange under the medial plane. Part Three Design of The Medial Pivot kneeObjective:To design a medial pivot knee system to achieve a normal neutral anatomical path of motion with a total knee arthroplasty (TKA) using specific motion-guiding design features.Methods:The tibia initially was shaped correctly in the overhead view but was flat on its upper surface. At 0°flexion, the femoral component was embedded into the tibial surface by 6 mm, and a boolean subtraction was carried out creating a depression in the tibia. The femoral component was flexed, displaced posteriorly, and rotated about the center, and another boolean subtraction performed. This procedure was repeated at flexion intervals from 0°to 135°, during which the femur was displaced linearly with flexion to a total of 12 mm and was rotated linearly with flexion to a total of 20°.Results: Describing three-dimensional knee motion by rigid body analysis has shown that during flexion, there is a posterior translation of the center of the femur and an internal tibial rotation. This motion is closely equivalent to only an internal rotation about a vertical axis through the medial tibial plateau. A special insert was generated.Conclusion: Knee kinematics of nature knee is medial pivot.The tibial bearing surfaces are shaped so that normal knee motion is possible without a cam.Part Four Kinematics Study on the Medial Pivot Knee of Chinese in Total Knee ArthroplastyObjective:To develop a three dimensional anatomical configuration model of the human knee , and validated to compute the kinematics of the medial pivot knee of Chinese in total knee arthroplasty. Methods:According to the model building principle from point to line to area to volume of mimics software, a three dimensional anatomical configuration model of the knee joint was reconstructed on the basis of the images of CT and MRI. In addition, quadriceps, ligaments and other soft tissues are defined as non-linear fiber, meanwhile simulating knee extension activity with input variable of quadriceps forces. We used the validated computer simulation of the knee joint to virtually insert the medial pivot knee of Chinese, then, flexed the knee from 0°to 120°。Recorded the angles of flexion of the knee and rotation of the tibia along time; the contact area of lateral femoral condyle with the insert.Results:When the knee was flexed to 120°, the angle of rotation of the tibia was 20°,and the lateral femoral condyle moved posteriorly.Conclusion:The medial pivot knee of Chinese can mimesis the nature knee, and the paradoxical movement was not presented.