Influencia del ángulo cervicodiafisario en la coxartrosis

Abstract

Coxarthrosis consists in the wear of cartilage at the hip joint and it is influenced by both mechanical and biological factors. In this work the biomechanical aspect is analyzed. In other investigations1 some models simplifications were made and the system was considered in two dimensions. Also the loads were not representative from the real situation because a constant body weight and few muscles, as abductor and adductor were used. Moreover during those analyzes the femur remained in a fixed position about the pelvis that is not the one where the maximum loads usually take place. In the present research, variations in the anatomy of the hip system were analyzed to understand cartilage behaviour. The aim is to observe how and where cartilage loads occur preferably during regular activities. Different hip configurations 3D models were performed to understand the response of the cartilage in patients with hip systems considered as irregular. For this purpose, the finite element method was used. From one configuration to another, the neck shaft angle, the acetabular anteversion and the femoral anteversion were varied. All configurations were analyzed for common daily activities, i.e. normal walking, going up stairs and standing up from a chair. The present 3D models took into account the loads from all the muscles involved in such movements, the variation of the body weight along the cycles, and also the appropriate rotated position of the femur with respect to the pelvis. The results show a growing tendency of the local loads and stresses at the cartilage when the hip system was not that considered as regular by the medicine. Also it can be appreciated very close contact pressure values and similar path contacts to those found by other researchers, Anderson et al.2. Such similarities helped to validate the present model considering that are comparable models and responses obtained are close. The contact areas that were more likely to suffer higher loads, for each angular variation and anatomy, can be appreciated in the results section. A factor that took into account the repeatability of daily activities was used to analyze which of the anatomies tested could be more harmful, giving the femoral anteversion of 20 degrees the worst combination of loads and frequency activity. After analyzing the results obtained, it could be concluded that the only two angular variations that were not detrimental to cartilage could be when the neck shaft angle was 110 degrees or when the acetabular anteversion was 10 degrees. All other anatomies tended to increase cartilage loads. In addition, as the influence of the activity was analyzed, results could be useful to prevent or avoid actions in given patients, depending on the anatomy of their bones.