Design Of The Medial Pivot Knee Prosthesis And Related Kinematic Study

This article is based on the anatomical study of femoral distal resection surface,femoral extermal rotation degree and tibial proximal resection surface of Chinese.Combined with the philosophy of medial-pivot kinematic and on the basis of Chinese anatomy,propose the medial-pivot design of the femoral component,tibial tray and tibial insert.Therefore it has important theoretical and practical value for the research and development of knee prosthesis.Firstly,using the software Unigraphic NX10.0(Siemens,Germany),and refer to the mentioned result of Chinese anatomy study,modify the prototype models of knee implant.Meanwhile based on the medial-pivot kinematic philosophy,design the new medial-pivot implant of femoral component and tibial tray.Secondly,by the kinematic study of natural knee joint,design a medial pivot knee system to simulate the movement of the natural knee.As regarding to the study of the natural knee motion,it has shown that during the flexion of knee,there is a posterior translation of the center of the femur,and an external rotation of the femur through the center of tibial medial plateau,while the tibia is internal rotated.At sagittal plane,the knee joint is almost hinge movement.Simulating the nature knee movement by using the software Unigraphic NX 10.0(Siemens,Germany),a boolean subtraction technique of the software was used to create a contacted depression on the tibial insert with the femoral condyle.Thirdly,developing a 3D anatomical model of the natural knee joint,conducted the initial validation of kinematic.According to the 3D anatomical model of the natural knee,simulated the routine total knee arthroplasty,implanted the new medial pivot knee prosthesis system to validate the knee kinematic movement,measured the related movement and the position of contacted surfaces between the femur and tibia.While the knee flexed from 0 degree to 120 degree,recorded the angles of flexion of the knee and rotation of the tibia,and recorded the contacted area between the lateral femoral condyle and the tibial insert.Based on above,we found that when the knee flexed to 120 degree,the internal rotation angle of the tibia was 20 degree,and the lateral femoral condyle moved posteriorly.Finally,based on the simulated total knee arthroplasty with the 3D anatomical model,and the sawbone activity with the prototype implantation,the new medial pivot knee system can simulate the nature knee joint,and the paradoxical movement was not presented.