Three-dimensional Finite Element Analysis Of Resurfacing Arthroplasty Of Hip For Osteonecrosis Of The Femoral Head

Purpose To construct different 3-D FE Resurfacing Arthroplasty of Hip(RSAH) models and to explore the biomechanics influences of the angle of femoral prosthesis implantation and to observe the biomechanics influences of the bone quality and the biomechanics influences of the necrosis size on femoral head and try to establish a standard for the patient selection of Resurfacing Arthroplasty of Hip(RSAH) and choose a suitable implant oritation.Materials and Methods 1.eighteen different angle of femoral prosthesis Implantation RSAH 3-D FE models were constructed with different bone quality.2. Forty-five different volume and different depth of necrosis 3-D FE models were constructed.3.Put a kind of pressure on each model which simulation of normal walking.4.analyze the regular pattern of the stress distribution on different model.Results 1. RSAH modals with different angle of femoral prosthesis Implantation and different bone quality:①stress concentration presented at head-neck junction part of the resurfaced femur.②the location of the neutrosphere in both the femoral prosthesis and the femoral neck bone is consistent with the position of the femoral prosthesis. the neutrosphere of cancellous bone underlying the femoral prosthesis presented at the superior and lateral part.③the location of maximum stress node in both femoral prosthesis and femoral neck cortical bone become different with the change of femoral prosthesis position. The location of maximum stress node in cancellous has nothing to do with the femoral prosthesis position. the maximum stress value increases with the increasing of the femoral prosthesis implantation angle and this tendency is not obviously when the angle range from 135°to 145°.④he neutrosphere location changes with the change of the femoral prosthesis implantation angle. The compressive area expands with the increasing of the the femoral prosthesis implantation angle.⑤when the angle range from 135°to 145°, there is no node of compressive/tensile stress value exceeding the yield stress value in the femoral prosthesis and in the cancellous bone underlying the femoral prosthesis and in the femoral neck cortical bone. these kinds of nodes exist in the femoral neck cancellous bone when the angle ange from 135°to 145°, but this ratio is less than 1%. With the decreasing of the he femoral prosthesis implantation angle, this ratio increasing.⑥he pattern of the stress distribution has nothing to do with the bone quality,⑦the maximum stress of femoral prosthesis increases in osteopenia and in osteoporosis, the maximum stress of femoral neck cortical bone increases both in osteopenia and osteoporosis. While the maximum stress of cancellous bone decreases.⑧The ratio of nodes over the yield stress inceases with the happening of osteopenia and osteoporosis, especially in osteoporosis, In steopenia, when the angle of femoral prosthesis Implantation is 140°, The ratio of nodes over the yield stress is less than 1%.2. RSAH modal of different exent of femoral head necrosis:①Stress concentration of bone coment which filling necrosis area presented at coment-bone junction. Stress concentration of the other part of femoal head and neck bone presented at head-neck junction part in the resurfaced femur.②the location of maximum stress node of bone coment which filling necrosis area is different with the different exent of the necrosis volume and depth, the location of maximum stress node in the other parts of the femoral head and neck is relative fixative.③the maximum stress value in bone coment of filling necrosis area increases with the increasing of the necrosis volume and depth. the maximum stress value in the other parts of the femoral head and neck decreases with the increasing of the necrosis volume and depth.④there is no node of compressive/tensile stress value exceeding the yield stress value in the bone coment of filling necrosis area and in the cancellous bone underlying the femoral prosthesis and in the femoral neck cortical bone. these kinds of nodes exist in the femoral neck cancellous bone. But this ratio is less than 1%. this ratio has nothing to do with the exent of the necrosis volume and depth.⑤the neutrosphere location is relative fixative in different exent of the necrosis volume and depth.⑥most serious areas of stress shielding in the cancellous bone underlying the femoral prosthesis presented at bone coment-bone junction. most serious areas of stress shielding in the femoral neck presented at prosthesis-bone junction.⑦the exent of stress shielding increases with the increasing of the exent of the necrosis volume and depth. when the depth≤25mm and volume≤55% or depth>30mm and volume<30%, The surface nodes ratio of stress shielding over 30% increases gently. When the depth>30mm and volume>30%, this ratio increases obviously.Conclusion after RSAH, The suitable angle range of femoral prosthesis Implantation is from 135°to 145°with nomal bone. The suitable angle of prosthesis implantation is 140°with osteopenia. Osteoporosis is not suitable for RSAH. the extent of stress shielding increases with the increasing of the depth and volume of osteonecrosis. The RSAH is suitable for the patient with the depth of osteonecrosis≤25mm and volume of osteonecrosis≤55%. RSAH is not suitable for the patient with the depth of osteonecrosis≥30mm and volume of osteonecrosis>30%.