[Influence of acetabular cup design on the primary implant stability : an experimental and numerical analysis]

An adequate primary stability and a subsequent stable osseous fixation (secondary stability) of artificial hip cups are required for long-term implant survival. The aim of this study was to analyse the design of cementless press-fit cups as an influencing factor of primary stability.Different hemispherical and conical cup designs were analysed. The fixation stability of the cups was detected experimentally using a spongiosa and a cortical model based on artificial bone as well as a numerical simulation using a spongiosa model by pull-out and lever-out tests. In addition, the stress on the osseous cup cavity was determined in the finite-element analysis.All tested cup designs revealed higher fixation stability in the cortical bone model compared to the spongiosa model. The experimental tests did not show an increase of fixation stability with the conical cup profile in comparison to hemispherical cup profiles.Therefore, cementless press-fit cups with conical cup profile do not provide a higher primary stability in comparison to hemispherical cups. Moreover, the stress on the bone cavity was lower inserting the hemispherical cup profiles in contrast to the conical profiles.