Contact conditions at the total hip head-neck modular taper junction: known knowns, known unknowns, or unknown unknowns?

This study employed a novel, micro-grooved finite element model to characterize the contact mechanics at the total hip head-neck modular taper junction during implant assembly under different conical angles and head taper surface topography. Modeling the head taper as an idealized “flat” surface led to a 19% reduction in the contact pressure at the interfaces and no plastic deformation of the stem taper micro-grooves as compared to the rough head taper model. Retrieved implants clearly show that plastic deformation occurs in vivo, therefore failing to consider the stem and head taper surface finish may lead to incorrect conclusions.