Analysis Of Finite Element Modeling On Adults Developmental Dysplasia Of The Hip And Total Hip Replacement

Part 1 Three-dimensional Finite Element Model of the Adults Developmental Dysplasia of the Hip:construction and stress analysisObjective To construct three-dimensional (3D) finite element models of the normal hip and adults developmental dysplasia of the hip and analyze stress distributions in the hips of different types.Methods 3D models of the normal human hip and different type adults developmental dysplasia of the hips were constructed from lamellar CT images with Mimics software, and then converted to 3D finite element units by Ansys10.0 software. Mechanical parameters were used to construct 3D finite element hip models. With the application of hip joint loading, stress changes of hips were measured. The models were tested and their stress distributions were compared.Results The constructed 3D finite element hip models clearly reflected the rea1 hip anatomy and biomechanica1 behavior of patients.The magnitudes of peak contact pressure differed between apposed articular surfaces of different type hips. It was found that the pressure concentrated at the superior dome cartilage of femoral head and acetabulum in normal,dysplasia and low dislocation models. There were some redundant high pressure occurred at the area near posterior-superior rim only in the dysplastic and hip low dislocation models. In high dislocation model, there were high pressure occurred at the area near front-superior dome cartilage of femoral head, and there is no contact ressure occurred at the area of cartilage of real acetabulum. In the normal hip the hightest Von Mises stress of cartilage of femoral head and acetabulum were 2.02 MPa and 2.37 MPa; In the dysplasia hip the hightest Von Mises stress of cartilage of femoral head and acetabulum were 4.23 MPa and 5.43 MPa; In the low dislocation hip the hightest Von Mises stress of cartilage of femoral head and acetabulum were 8.45 MPa and 10.32 MPa; In the high dislocation hip the hightest Von Mises stress of cartilage of femoral head and acetabulum were 8.67 MPa and 0.59 MPa. The distribution of bone below cartilage in femoral head and acetabulum were like it of cartilage of femoral head and acetabulum, There were some redundant high pressure occurred at the area near posterior-superior rim only in the dysplastic hip and low dislocation models. In the normal hip the hightest Von Mises stress of femoral head and acetabulum below cartilage were 8.65 MPa and 2.52 MPa; In the dysplasia hip the hightest Von Mises stress of femoral head and acetabulum below cartilage were 8.92 MPa and 2.73 MPa; In the low dislocation hip the hightest Von Mises stress of femoral head and acetabulum below cartilage were 10.65 MPa and 4.02 MPa; In the high dislocation hip the hightest Von Mises stress of femoral head below cartilage and fake acetabulum were 8.17 MPa and 8.59 MPa.Conclusion An more precise 3D finite element model of nomal and adults developmental dysplasia of the hip acetabulum can be constructed with lamellar CT images and Mimics software.and also provides a reasonably and efective model for biomechanical analysis of adults developmental dysplasia of the hip.Part 2 Finite Element Analysis of Acetabular Ingression Insert in Total Hip ReplacementObjective To construct three-dimensional(3D) finite element models of acetabular ingression insert in total hip replacement , and analyze the stress distributions in the prothesis and to provide a theoretical basis for clinical work.Methods 3D models of the normal human acetabulum was constructed from lamellar CT images and acetabular prosthesis was developed through AUTOCAD by actual parameter. 3D finite element models of different center acetabular prothesis which were impacted according clinic operate were developed. With the application of hip joint loading, stress changes of prothesis were measured. The models were tested and their stress distributions were compared.Results The center of acetabular prothesis affected the resulting contact stress markedly.The peak contact stress values were found in the inner surface of polyethylene. The more distance ingression insert, the higher contact stress occure in polyethylene and linked part of prothesis neck and head. When acetabular in normal center, the hightest Von Mises stress in inner surface of polyethylene was 4.24 MPa and linked part of prothesis'neck and head was 17.02 MPa; When there is 3 mm between acetabular and iliopectineal line, the hightest Von Mises stress in inner surface of polyethylene was 4.35 MPa and linked part of prothesis'neck and head was 17.78 MPa , increased 2.59% and 4.47%; When acetabular prothesis attach iliopectineal line, the hightest Von Mises stress in inner surface of polyethylene was 4.70 MPa and linked part of prothesis'neck and head was 18.93 MPa, increased 10.85% and 11.22%; When acetabular prothesis overtopping iliopectineal line 3mm, the hightest Von Mises stress in inner surface of polyethylene was 4.97 MPa and linked part of prothesis'neck and head was 20.50 MPa, increased 17.22% and 20.45%; When acetabular prothesis overtopping iliopectineal line 6mm, the hightest Von Mises stress in inner surface of polyethylene was 5.67 MPa and linked part of prothesis'neck and head was 25.36 MPa, increased 33.73% and 49.00%.Conclusion When acetabular ingression insert in total hip replacement, higher contact stress values were occured in the inner surface of polyethylene and linked part of prothesis'neck and head . When prothesis exceed iliopectineal line, contact stress values were increased obviously.Part 3 Finite Element Analysis of Different Anteversion Insert Femoral Prothesis in Total Hip ReplacementObjective To construct three-dimensional(3D) finite element models of the different anteversion insert femoral prothesis in total hip replacement and analyze the stress distributions in femur and prothesis, and to provide a theoretical basis for clinical work.Methods 3D models of the normal human femur was developed through lamellar CT images and femoral prosthesis was developed through AUTOCAD according actual parameter. 3D finite element models of different anteversion insert femoral prothesis which were impacted according clinical operation. With the application of hip joint loading, quantitatively measure stress changes of femur and femoral prothesis were measured.Results (1) Compared with intact femur, insertion of femoral prothesis into the femoral canal decreased the proximal femoral stresses level, especially in calcar femorale and femoral tuberositas. However, the stress in the bone near the prosthisis distal end augmented. The stress of 0°and 30°anteversion angle insert femoral prothesis were smaller in calcar femorale, femoral tuberositas, higher in the bone near the prosthisis distal than that of 15°. (2)There were higher stress in femoral prothesis of 0°and 30°anteversion angle insert femoral prothesis than that of 15°. There were higher stress in interface-load of 0°and 30°anteversion angle insert femoral prothesis than that of 15°. (3) In the plane of osteotomy, insertion of femoral prothesis into the femoral canal decreased the proximal femoral stresses level, especially in calcar femorale and femoral tuberositas, the prothesis bear more stress. This phenomenon were obvious in the model of 0°and 30°anteversion angle insert. (4) The micromotion of prothesis were higher in the prothesis of 0°and 30°anteversion angle insert, compared with 15°anteversion angle insert.Conclusion Insertion of implants induced significant stress shielding in the proximal femur, especially at calcar femorale and femoral tuberositas, concentrated in the prosthesis distal end. In the 15°anteversion angle insert femoral prothesis model, the load distribution is even, micromotion is low, stability is high, so it has excellent biomechanics characteristics.