A Finite Element Research On The Treatment Of Osteonecrosis Of Femoral Head By Porous Tantalum Rod

Objectives:1. To develop and validate an finite element model of upper femur of a normal healthy person.2. With three-dimensional finite element method, to develop different finite element models of upper femur implanted with porous tantalum rod and fibula at different locations.3. To analyze the deformation and displacement of the femoral head and the best position of the tantalum rod implantation by finite element method, in order to provide theoretical basis for the clinical using of porous tantalum rod to treat the osteonecrosis of the femoral head and reduce the collapse after the femoral head necrosis.Methods:1. The three-dimensional finite element model of normal upper femur was developed by thin slice CT scan of a healthy male adult and finite element softwares, and the model was validated.2. On the basis of the normal model, the other21different finite element models imitating tantalum rod implanting at different positions, fibula implanting and decompression of osteonecrosis of different extents were developed, divided in7groups.3. By using the Abaqus software, to explore the deformation and stress of the22models, and to analyze the data by SPSS16.0software in order to investigate the best position of the tantalum rod implantation and the relation between the deformation tendency of the femoral head and the tantalum rod implantation.Results:1.The finite element model of normal upper femur was developed, including185,193nodes and526,303elements.2.21models, in7groups, were developed to imitate the deformation and stress conditions after various treatments of the osteonecrosis with different range(60°,90°and120°), including core decompression, fibula implantation and porous tantalum rods implantation at different positions. And the models were validated.3. The collapse of different models were not statistically significant when the osteonecrosis of femoral head was60°(P>0.05); the collapse of necrotizing zone medial implantation model was significantly smaller than that of necrotizing zone lateral implantation model (P<0.01). When the femoral head necrosis was60°, only the artificial bone stress of necrotic zone medial implantation was statistically significant compared with the stress of shorten implantation model (P <0.01); when the necrosis was120°, the artificial bone stress of necrotic zone medial implantation was significantly smaller than that of necrotic zone lateral imp lantation(P<0.01).Conclusions:1.The finite element model of normal upper femur was validated and could be used on further model developing.2. The21different finite element models were validated and could be used to analyze the deformation and stress of the corresponding upper femurs.3. With certain osteonecrosis region of the femoral head, the nearer the tantalum rod was implanted to the medial part of the necrotic zone, the smaller the collapse of the corresponding weight-bearing area of the femoral head; when the osteonecrosis was60°, the collapse of the weight-bearing area had little to do with the tantalum rod implantation position. When the osteonecrosis was120°, the implantation of the tantalum rod at the medial part of the necrotic zone and shorten implantation of the rod by5mm could reduce the collapse significantly; with a larger necrotic zone, the implantation of the rod at the medial part of the necrotic zone could reduce the stress of the artificial bone surface efficaciously; when the necrosis was120°, the fibula implantation or the shortening implantation of the tantalum rod would achieve relatively better outcomes, which might reduce the collapse of the weight-bearing area and the stress of the artificial bone surface.