Experimental Study Of Biomechanics On Effects Of Knee Joint By The Deformity Of Genu Varum And Genu Valgum

Objective: Finite element method and photoelastic experiment were used to study the principle of stress and strain on knee joint from genu varum 30 degree to genu valgum 30 degree. Biomechanics proofs were provided about it's bad effects and treatment on clinical.Methods: According to X-rays of genu varum and genu valgum and cross-section CT of normal knee joint, 31 planar-models and 31 working conditions in three-dimensional finite element were established with the software of Super-Sap every 2 degree from genu varum 30 degree to genu valgum 30 degree, then calculated the stress and stain state of every node with the size and direction of actual stress. In planar-photoelastic experiment, transparent Epoxy Resin materials were formulated according to the practical Young's elastic modulus of the knee bone tissue, then cut as the shape of the knee on X-rays and put them in the polarized light field with loads to observe the stress stripe of interference, thus the stress state of the knee joint can be comprehend.Results: 1 % There was compressive stress on the interior and outer sides of normal knee, while the stress on interior side was one and half multiple than that of outer side. The maximum stress was onentocondyle of femur. 2. Stress on the interior side of knee increased according to the enlargement of the angle of introversion. The change of stress was obvious from 1 0 to 18 degree, while changes mainly existed on the interior tibial plateau. Stress concentrated obviously center and outer of the articular cartilage-meniscus complex. 3, Stress on the outer side of knee increased little from 0 to 12 degree and increased obviously when the angle greater than 20 degree according to the enlargement of angle of exstrophy. Stress mainly concentrated outside of the tibial plateau and center and inboard of the complex.Conclusions: 1 , Stress mostly transmitted through the medial of the normal knee joint. 2. The trend of damage on the interior side of knee, especially inboard of tibial plateau, enlarged according to the increase of angle of introversion, while the center and outer of the complex became easily injured. Introversion from 10 to 14 degree is possible critical angel of the beginning of damage and the precaution of complication after osteotomy. 3 ^ The easiest damage area is outside of the tibial plateau and center and inboard of the complex according to the enlargement of the angle of exstrophy. Exstrophy greater than 20 degree is possible critical angel of the beginning of damage and the precaution of complication after osteotomy. 4?Nothing but from biomechanics side, it is acceptable between introversion 6 degree and exstrophy 1 0 degree after osteotomy.