Abstract
Interface strength is considered as one of the most influential factors in the long-term durability of the replaced joint in cemented total hip replacement. Several researchers have suggested that the damage initiation in a replaced joint is a mechanical phenomenon primarily taking place in the vicinity of cement-prosthesis interface. In this study, the fracture behavior of a crack at the interface of cement-prosthesis was investigated both experimentally and theoretically under static loading conditions. The finite element method, and then the maximum tangential stress (MTS) and the generalized MTS (GMTS) criteria were used for theoretical study of interface fracture. Some experiments were also carried out to investigate the effect of cement mixing methods (hand mixing and vacuum mixing) on crack growth pattern. The results showed that the vacuum-mixed cement led to self-similar crack growth along the cement-prosthesis interface, while the crack kinked into the cement in the samples prepared by hand-mixed cement. Then some experiments were performed to verify the theoretical results obtained for mixed mode fracture angles in the samples prepared by hand-mixed cement. The sandwich Brazilian disk model was used in both finite element and experimental approaches to simulate the cement-prosthesis interface. The experimental results were found to be in good agreement with those predicted by the GMTS criterion.
Highlights
In the early 1960s, Sir John Charnley introduced a new method, using acrylic bone cement (PolyMethylMethAcrylate, PMMA), to fill the space between the prosthetic stem and bone, which has been a brilliant practice for hip joint replacement (Ohashi, 2000)
The fracture loads obtained for the samples prepared by the two vacuum mixing methods can be compared with those of the samples prepared by hand mixing
The experimental results showed that for all samples prepared by vacuum mixing method, fracture occurred at the cement-prosthesis interface and the crack did not kink into the cement
Summary
In the early 1960s, Sir John Charnley introduced a new method, using acrylic bone cement (PolyMethylMethAcrylate, PMMA), to fill the space between the prosthetic stem and bone, which has been a brilliant practice for hip joint replacement (Ohashi, 2000). M. Choupani et al./ Investigation of fracture in an interface crack between bone cement and stainless steel biological and mechanical factors may cause the joint damage, while the preliminary defects after surgery are suggested to be mainly mechanical (Tong et al, 2007). There are some evidence indicating the separation of prosthesis from cement in samples used for more than four years, even when the bone-cement interface survives (Ohashi, 2000). These factors demonstrate the significance of investigating the cementprosthesis connection. The Brazilian disk sample is a widely used model providing the loading mode conditions from mode I to mode II as a function of loading angle
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