Bio-Medical Materials and Engineering - Volume 9, issue 4

Authors: Lewis, Gladius

Article Type: Research Article

Abstract: The goal of the present work was to establish the relative influence of one exogenous variable versus one endogenous variable on the fully‐reversed tension‐compression fatigue performance of bone cement. The method used to mix the cement constituents was the exogenous variable, while the viscosity of the mixed cement dough was the endogenous variable. Two commercial cement formulations (Palacos® R and Osteopal® ) and two cement mixing methods (hand mixing and vacuum mixing) were used. It was found that for a given mixing method, cement viscosity exerts a marginal influence on fatigue performance. On the other hand, for a given …cement formulation, vacuum mixing led to a statistically significant improvement in fatigue performance. The present results demonstrate the superior influence of mixing method over cement viscosity. Show more

Keywords: Acrylic bone cement, fatigue, mixing method, cement viscosity

Citation: Bio-Medical Materials and Engineering, vol. 9, no. 4, pp. 197-207, 1999

Authors: Rao, S. | Shirata, K. | Furukawa, K.S. | Ushida, T. | Tateishi, T. | Kanazawa, M. | Katsube, S. | Janna, S.

Article Type: Research Article

Abstract: We established a novel method to investigate the phagocytosis of ultra high molecular weight polyethylene using primary macrophage cells by an inverted cell culture method. Abundant wear debris derived from implant materials are generated in aseptic loosening and are deposited in periprosthetic tissues in which they are phagocytised by mono‐ and multi‐nucleated macrophage like cells. Ultra‐high‐molecular‐weight‐polyethylene wear debris generated from different sources namely, from laboratory test wear machine, in vivo methods and from knee and hip simulator were mainly used in this investigation. The cytotoxicity index of the different UHMWPE particles obtained from various sources were compared with that of …the PE beads and the control without particles by Alamar Blue and Neutral Red assays. The results showed that the cytotoxicity index was significantly lower for the wear debris from the in vivo experiments than that for other particles. SEM analysis were also done to understand the morphology of the wear debris and polyethylene beads and to confirm the phagocytosis process. The mean diameter of the wear debris obtained from the in vivo experiments as estimated from the imaging analysis of the SEM photographs was found to be the least. The inverted cell culture method may be regarded as one of the good methods to study the phagocytosis of UHMWPE by macrophage cells. Show more

Keywords: Inverted cell culture, phagocytosis, UHMWPE wear debris, SEM

Citation: Bio-Medical Materials and Engineering, vol. 9, no. 4, pp. 209-217, 1999

Authors: Jian, C.Y. | Yokobori, Jr., A. Toshimitsu

Article Type: Research Article

Abstract: It is necessary to maintain mechanical compatibility between a blood vessel and a vascular substitute to promote encapsulation around the anastomosed part. From this point of view, using linear elastic theory, we had previously performed stress analyses at the part anastomosed by tissue adhesion, in order to propose some methods of preventing stress concentration at this junction. In this study, based on the previous analyses, we have attempted to develop a concept that can be applied under the conditions of operation. That is, the initial diameter of a vascular substitute with high rigidity is chosen larger than that of a …blood vessel. This will reduce the stress concentration around the anastomosed part, on average, during expansion of the blood vessel. We analysed the optimum diameter ratio between the vascular substitute and the blood vessel which causes the least stress concentration, on average, during this process, using linear elastic theory. Furthermore, numerical analyses of blood vessel deformation were performed using various nonlinear stress–strain laws. These results were compared to the analytical solution based on linear elastic theory. Show more

Keywords: Blood vessel, vascular substitute, anastomosed part, stress analysis, linear elastic theory, nonlinear stress–strain law

Citation: Bio-Medical Materials and Engineering, vol. 9, no. 4, pp. 219-231, 1999

Authors: Huang, Shyh‐Chour

Article Type: Research Article

Abstract: The objective of this study is to simulate the dynamic response of the temporomandibular joint forces within a rear‐end impacted vehicle. Clinicians reports symptoms of temporomandibular joint disorders in many patients who have experienced vehicle rear‐end impacts. In rear‐end impact, a vehicle occupant’s head is thrust rearward with respect to the vehicle in a whiplash action. During this motion, complex dynamic forces act on the jaw bone. To understand the dynamic forces acting on the jaw, we extended an existing human head/neck model by adding a movable jaw, and performed simulation of the jaw motions during rear‐end impacts at 4.2, …6.4 and 9.6 m/s. Results predicted temporomandibular joint torques, relative angle between the head and jaw, jaw angular acceleration and linear acceleration of the jaw’s center of mass. Show more

Keywords: Temporomandibular joint, head/neck/jaw model, rear‐end impact

Citation: Bio-Medical Materials and Engineering, vol. 9, no. 4, pp. 233-241, 1999

Authors: Ploeg, Heidi‐Lynn | Wevers, Henk W. | Wyss, Urs P. | Bürgi, Maja

Article Type: Research Article

Abstract: Component fatigue testing, the final step in the development of total joint replacements, is performed to validate the safety of these components against fatigue failure before clinical use. Fatigue test prediction can aid the design of an efficient fatigue‐testing program. The objective of this study was to perform an efficient and accurate statistical analysis of component fatigue test results, for the validation of future fatigue test predictions. Testing was performed with two aims: first, to determine the local component stress–force relationship using strain gauges; and second, to provide a statistical description of the fatigue test results. Forty‐nine hip stems, in …three sizes, were tested in a series of static and fatigue tests. Through effective planning and analysis, a statistical description of the component fatigue test results was determined including, 3‐parameter Weibull distributions of life at two stress levels and log‐Normal distributions of fatigue strength at various lives up to 5 million cycles. Show more

Keywords: Fatigue, statistics, hip stem, fatigue testing, strain gauge testing

Citation: Bio-Medical Materials and Engineering, vol. 9, no. 4, pp. 243-263, 1999