IMPACT OF GEOMETRIC PARAMETERS ON THE CHOICE OF A CUSTOM FEMORAL IMPLANT

Abstract

In this paper, the effects of both geometric parameters and mineral density on the evolution of stresses generated in a cementless hip implant are investigated to enable orthopedic surgeons to make an appropriate selection. A design of experiment was used, followed by the analysis of variance (ANOVA) to identify the effects of geometric and physical parameters in terms of bone density on a femoral implant. Twenty-seven implants of different geometric dimensions were considered, without modification of the topology. Multiple regression analysis was chosen to replace the finite element method to predict the level of stresses generated in the stem, in terms of life expectancy, allowing for optimal geometric parameter selection. Three parameters of the stem were selected, namely, stem length (SL), neck length (NL), and neck shaft angle (NSA), where each parameter is apprehended by three levels. Based on a design (3[Formula: see text], 27 femur–implant CAD models were created, to analyze the effect of three limiting densities (low, medium, and high) for the estimation of maximum stresses by finite elements. The results obtained by ANOVA for the three densities, respectively, for the low density the SL had an impact of the order of 58.5% on the level of von Mises constraints followed by the NL and NSA. For the medium density, it was observed that the SL remains the most influential parameter, with a rate of 41.2%, while for the high density the NL becomes the most influential (37.5%) followed by the SL and the NSA. The regression model used showed very good accuracy in terms of predicting the level of von Mises stress, compared to the results obtained by the finite element method.