Biomechanical Assessment Of Simple Skeletal Tuberculosis Of Acetabular By Finite Element Method

Objective:Establish3D finite element model of an adult normal hip joint and the simple skeletal tuberculosis of acetabular, using finite element analysis method to analyze the stress and strain on the simple skeletal tuberculosis of acetabular and the displacement of the hip joint, researched theirs biomechanical changes.Method:First, according to the adult normal hip joint CT date by the means of thin layers,use Minics10.0software to carry out3D solid mode1.use Geomagic5.0software to optimize this model, then use ANSYS10.0finite element software to establish the normal hip joint3D finite element model and the simple skeletal tuberculosis of acetabular3D finite element models, including the simple skeletal tuberculosis of the top of acetabular, the simple skeletal tuberculosis of the center of the acetabulum, the simple skeletal tuberculosis of the anterior acetabular, and the simple skeletal tuberculosis of the posterior acetabular. the last, simulate the situation of standing on one leg, utilize these hip-joint models to load, analyze and calculate the peak Von Mises stress of the cartilage of the hip-joint, subchondral bone and the tubercular abscess, and the initial micro displacement of subchondral bone. Results: The construction of3D adult normal hip joint model (Model A) was divided into269284nodes and184786tetrahedron elements, and The loading tests showed:the values of the peak Von Mises stress of the subchondral bone of acetabular, the cartilage of acetabular, the subchondral bone of femoral head and the cartilage of femoral head, were3.14Mpa,3. lOMpa,10.25Mpa,4.07Mpa. Compared with the peak Von Mises stress of the normal hip, the simple skeletal tuberculosis of the top of acetabular (Model B) followed by an increase of84.08%,31.29%、14.93%、29.98%; the simple skeletal tuberculosis of the center of the acetabulum (Model C) followed by an increase of3.50%、16.77%、6.83%、16.71%、; the simple skeletal tuberculosis of the anterior acetabular (Model D) followed by an increase of21.34%、20.65%、1.17%、5.65%; the simple skeletal tuberculosis of the posterior acetabular (Model E) followed by an increase of66.56%、28.39%、10.73%、23.10%; the value of the peak Von Mises stress of tubercular abscess were0.7766Mpa (Model B),0.101OMpa (Model C),0.2036Mpa (Model D),0.5557Mpa (model E).And the initial micro displacement of the subchondral bone of acetabular and femoral head were0.33mm、0.44mm. Compare with the model A, the model B followed by an increase of66.11%、40.33%; the model C followed by an increase of11.13%.39.19%; the model D followed by an increase of17.28%、49.44%; the model E followed by an increase of29.05%、54.98%.Conclusion:The3D finite element models which were established can reflect the biomechanical characteristics of the hip and the simple skeletal tuberculosis of acetabular, and have a high precision and mechanical simulation; the research shows that the simple skeletal tuberculosis alters the stress distribution at the hip. And due to the existence of the tuberculous abscess, there is a stress concentration at the osseous tissue which is surround the abscess, the decreased contact area and concentrated loading results in greater contact stresses and more acetabular Deformation, so lead to have a risk of subchondral bone collapse; the model B and model E have greater changes of the situation of pressure distribution than model C and model D, the more stresses, the more deformation, and a higher risk of subchondral bone collapse.