Analysis of cartilage loading and injury correlation in Knee varus deformity

Abstract Objective: The purpose of this study is to construct three-dimensional simulation models of Knee osteoarthritis (KOA) with different varus angles by applying computer-aided design (CAD); to analyse the stress distribution in the knee joint cavity by using finite elements through the KOA models of different varus, and to compare the internal loads in the knee joints of different models; and to carry out a correlation analysis of the results of the finite element analyses in conjunction with the corresponding clinical cases of varus and cartilage injuries. Methods: The CAD software package Mimics 21.0 was used to accurately simulate different varus angle models, and the simulated varus angles were divided into (0°,3°,6°,9°,12°,15°,18°) seven knee models, which were processed with finite element software, and axial forces were applied by simulating the weight of the human body in the static extension position, and the cartilage of the femoral condyle, medial tibial plateau, and lateral plateau were obtained. Von-Mises Stress (VMS) distribution and peak conditions, combined with clinical cases of the same varus deformity angle intraoperative microscopic visualization of cartilage cartilage injury, to find the cartilage force and injury correlation. Results: Under a compression load of 740N, the lower limb mechanical axis shifted inward as the varus angle increased；the peak VMS of the lateral tibial plateau and femoral condyles did not change much from 3°-18°, the peak cartilage VMS of the medial tibial plateau was higher than that of other intercompartments；The medial tibial plateau had the largest stress area at 0°, with a 2.6-fold increase in peak VMS from 4.13-14.05MPa from 0°-6°, and the stress loads basically stabilized from 6°-15°. Clinical data showed that the varus deformity angle was significantly correlated with cartilage damage in the knee, medial plateau, and patellofemoral intercompartment ( F1=52.287,P1<.001 ,h 1 2 =.709 , F2=312.67,P2<.001 ,h 2 2 =.729, F3=55.486,P3<.001 ,h 3 2 =.691) Conclusion: The larger the varus deformity angle, the higher the medial cartilage stress load, the heavier the cartilage damage in the corresponding peak stress area. In actual clinical patients, when varus exceeds 6°, in addition to sagittal plane medial plateau cartilage damage there was also coronal plane patellofemoral intercompartmental cartilage damage, and there was a situation of articular coronal plane motion, and the knee injury appeared abnormal when it exceeded 15°, which could be deduced that there was an abnormal motion of the knee joint. The probability of cartilage damage increases when the varus is ≥6°, and early surgical correction is recommended to prevent aggravation of the deformity and thus restore knee function.