Determinación del comportamiento biomecánico de una cadera displásica en un paciente de 1 año de edad: modelo 3D computacional

Abstract

The hip is one of the most important joints in the human being, since it supports the weight of the body during static and dynamic postures. Joint morphogenesis can be affected by abnormalities such as hip dysplasia, which focuses on the involvement of the acetabular cavity and the femoral head. Possible factors that can generate such a condition include nutrition, genetics, gender or a combination of these. However, the mechanical environment plays a major role in the degeneration of cartilage in the joint [1]. The applied load facilitates the flow of nutrients in the cartilage, in addition to providing essential mechanical signals for the normal maintenance of cells and tissues, even influences the endochondral growth process, due to this, excessive loads cause them to be affected biological processes such as correct growth and formation of the same hip [2] [3].

Because contact pressures and general biomechanics of the hip cannot be measured directly in vivo, finite element methods have been applied [4]. In this study, it was proposed to determine the biomechanical behavior of the dysplastic hip of a one-year-old infant. For this purpose, the reconstruction of a 3D computational model in a healthy state was made from computed tomography, which was subsequently modified to obtain two models with dysplastic conditions. From the review of the existing literature about the disease, conditions of change in the acetabular index were selected for the generation of the disease in the models, which had rates of 20 ° (healthy model), 25 ° and 30 ° (affected models).

The models were taken to the ANSYS 19.1 ® software in which they were duly resolved. A literature review of works related to the study of bone tissue was carried out to determine the properties of the materials that were assigned to each of the parts that make up the joint. The loading conditions applied were based on the standing model described by Pauwels [5]. In addition, the relevant contact conditions between the different bodies of the models were given and the meshing and their respective refining were performed, to subsequently give solution.

The results obtained showed evident changes in the stresses and contact pressures for the models with the greatest pathological involvement. Increases in joint effort were evidenced from 2,787 MPa in the healthy model to 6.9625 MPa in the most critical model and increases in contact pressures in acetabular cartilage from 2.8746 MPa to 7 MPa. These values ​​and their distributions were compared with data obtained from the existing specialized literature, in order to validate the study.