Effectiveness of analytical methods in predicting non-linear contact conditions in hard-on-hard hip implants

Contact mechanics models need to be developed for a comprehensive contact analysis in ball-on-socket joints. These models can be used consequently predict wear for non-linear, nearly conformal contacts in hard-on-hard hip implants. At present, some theoretical models are used to estimate the contact conditions in hip implants. The prediction of contact conditions in these nearly conformal contacts using analytical models may not be accurate due to their theoretical assumptions, and their accuracy must be verified. This study has comprehensively analysed the capability of existing popular Hertz and Fang theoretical models under various system parameters, particularly for hard-on-hard hip implants, and verified the results with finite element method (FEM). The models are analysed under different system parameters such as gait load, femoral head size, thickness of the acetabular cup, radial clearance and equivalent modulus of the tribo-pair. The contact parameters, such as the maximum contact pressure, contact radius and maximum deformation, are considered for the validation with FEM. Both analytical models fail to predict the contact conditions throughout a gait cycle. The limitations and discrepancies to be addressed in the existing analytical models are discussed, which will pave the way for developing a futuristic model for accurate contact analysis. Until now, FEM stands out as a precise method to analyse contact conditions in nearly conformal contacts.