The Measurement Of The Three-dimension Morphology Of The Healthy Chinese Knee And Related Research

To restore normal limb alignment is very important for the long time results of total knee arthroplasty. The geometric shape and the kinematics of prosthesis should match with those of normal knee so that they work in harmony with the remaining soft tissue structures around the knee .The accurate parameters of three-dimensional anatomy andgeometry of the knee were the foundation of prosthetic design and manufacture.Objective : To found the three-dimensional(3-D) solidmodel and to obtain the important parameters of the Chinesenormal knee by using computer-aided design (CAD) software . By exploring the correlation with prosthesis design of the knee joint, the results could provide a morphological basis for native knee prosthesis and make the foundation of the parameter database of the Chinese normal knee.Methods: The CT imaging data of 120 normal adult volunteers and 6 cadaver knees were obtained. Through CAD software, the 3-D solid models were reconstructed and therelated parameters of the Chinese normal knee were found. Totest the results obtained from CAD models, we measured the cadaver knees manully, realizing errors between two methods and analyzing causes.Results : The related parameters of the Chinese normal knee were found . The width of femoral condyle averaged 70. 46mm . The angles of medial and lateral femoral condyles were 82. 57 +3. 36 and 79. 86 +4. 33 , respectively . The anterior distance of tibial platform relative to femoral condyle and the posterior distance of tibial platform relative to femoral condyle were 50. 13+6. 89 mm and 5. 94 + 4.01 mm , respectively . On the sagittal plane, the distal articular femur may be represented by three circular surfaces. The distal radii of medial and lateral femoral condyles were 37.94 + 6.79 mm and 44. 07?. 38 mm , respectively .The radii of the distal condyles were between 1. 8 and 2. 1 times of those of the medial femoral condyles and the lateral femoral condyles . The distal angles of medial and lateral femoral condyles were 52. 62 +7.68 and 44.81 +4. 42, respectively. The posterior radius and angle of medial femoral condyle were not statistically different from those of the lateral femoral condyle (P>0. 05) . The distances from the geometric centers of the medial and lateral posterior condyles to the medial and lateral epicondyles were 2. 62+1. 17 mm and 3. 49+1.28 mm, respectively . The angle between the line of the geometric centers of the medial and lateral posterior condyles and thetransepicondylar axis was 4.31 +1.36 .The geometric parameters from CAD measurement are smaller than those from the manual. The mean errors were between 1. 33 mm and 2. 64 mm in radius parameters, and between 0. 73mm and 1. 31 mm in linear parameters.Conclusion : ㏕he widths of medial and lateral femoral condyles (24.72mm, 23. 55mm) were similar with those of medial and lateral tibial platforms (25. 06 mm, 27.98mm) . The width of femoral condyle was 1. 04 times of the width of tibial platform, whereas it was 1. 18 times of sagittal length of femoral condyle. There was positive correlation between the width of femoral condyle and the width of tibial platform (r=0. 71) . The width of the femoral condyle or the tibial platform might be taken as the knee.2The angles of medial and lateral femoral condyles were 82. 57 + 3. 36 and 79. 86 + 4. 33 respectively , which demonstrastrated that the medial and lateral femoral condyles did not run parallel to each other but appear to converge toward the patellofemoral groove . It was advantageous to make the patella steadily.(3)The distal radii of medial and lateral femoral condyles were 37. 94mm and 44. 07mm respectively , which were statistically lager than those of the posterior condyles (20. 62 mm, 21.09mm) .The radius of medial femoral condyle was smaller than that of the lateral femoralcondyle , whereas the angle of lateral femoral condyle (44.81) was smaller than that of the medial femoralcondyle (52.62) . The main distinctions of the medial andlateral fem...