Custom-made, titanium alloy hip-joint prostheses: a combined mathematical modelling, fatigue strength and microstructure study

Three mathematical models were developed in order to calculate stresses which occur in custom-made HERAMED prostheses during mechanical testing according to DIN 58840. Two of the models performed a three-dimensional stress analysis by using either the boundary element method or the finite element method. The third model was called the simple model and relied on a mixture of the simple bending theory, the beam-on-elastic foundation theory and the finite element method. Results from the mathematical models were compared with results from three-dimensional photoelasticity by stress freezing. The use of three-dimensional scattered-light photoelasticity was also evaluated. On the basis of the theoretical and experimental results, it was found that stresses in the prostheses can satisfactorily be calculated with the simple model. The simple model was also much less expensive in terms of computer resources than both the boundary and finite element methods. [Continues.]