| Total hip arthroplasty is the most effective treatment of choice for advanced hip osteoarthritis and its primary objective is to relieve severe pain, keep articular stabilization, improve articular function and adjust the length of lower extremities. At the present time, metallic implant materials remain most wide application in total hip arthroplasty and the aseptic loosening of the femoral prosthesis is one of the primary complications that affect the long-term curative effect. One of the loosening causes is that the elastic modulus of metal is far more than that of. femur (the elastic modulus of cobalt-based alloys is 220GPa and titanium-based alloys 110GPa, but femoral cortex only 18GPa.). So the combinationbetween metallic prosthesis and femur obviously does not create a better and approximate physiological mechanics environment because their mechanical compatibility is impossible. As a result of the high elastic modulus of metal and the poor mechanical compatibility between prosthesis and bone the widely applied total femoral prosthesis often causes stress shielding and stress concentration which results in osteoporosis, osteanabrosis and finally leads to prosthesis loosening, subsidence and other complications. These results bring difficult problems to the after revision of total hip arthroplasty. The article is based on the carbon fiber reinforced polyetheretherketone (CF/PEEK) that possesses lower elastic modulus and higher strength and explores the prospect that composite materials are used to manufacture femoral prosthesis. The purpose is to search the new femoral prosthesis that can integrate with femur compactly and increase proximal femoral stress transfer, and further improves the long-term curative effect of total hip arthroplastyBecause the elastic modulus of CF/PEEK is adjustable, this research attempts to make use of the three dimensional finite element technology to decide the suitable material,combination proportion of carbon fiber and PEEK, carbon fiber reinforcing orientation and spreading, and to develop CF/PEEK composite materials whose mechanical function should be superior to that of CoCrMo alloys and whose elastic modulus should be lower than that of CoCrMo alloys. Meanwhile, the CF/PEEK prosthesis is manufactured according to the geometry size of the simulated AML total hip femoral prosthesis that is made of CoCrMo alloys. In the article, the total hip femoral prosthesis has two layers, the inner layer is long carbon fiber reinforced PEEK composite and the outer layer is short carbon fiber reinforced PEEK composite.The femurs were loaded with 1000N and the femoral stress and strain were measured in the simulated walking state in which the body stood by single leg. And then, total hip replacements were performed with Cobalt-based alloy component and CF/PEEK composite component and simulated biological fixation. A series of biomechanical tests were adopted to measure the distributive law of stress and strain of proximal femur and the femoral prosthesis which had been replaced with Cobalt-based alloy component and CF/PEEKcomposite component and to measure the extent of stress-shielding of the femoral prosthesis, too; at the same time the micro-motion of the femoral prosthesis in the femoral marrow cavity was measured; and finally the anti-torsional strength tests and the breakage tests were performed. The torsional moment, the torsional angle and interface stress between the prosthesis and the femur in the femoral marrow cavity are measured, too. Statistics analysis was processed with SPSS10.0 software.The results show:(1) After total hip replacement was performed with two different material components, the proximal femur surface stress and strain in CF/PEEK group were measured and behaved higher than those in CoCrMo alloy group, the difference in statistics was significant (P<0.01), and the strain distribution of the former was close to that in normal femur and its the stress distribution was even more close to that in the physiological femur (P<0.01). This shows that th...
|
PDF Full Text Request