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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Zietz
C
C
Orthopädische Klinik und Poliklinik, Universität Rostock, Doberaner Strasse 142, 18057, Rostock, Deutschland. carmen.zietz@med.uni-rostock.de
Fritsche
A
A
Kluess
D
D
Mittelmeier
W
W
Bader
R
R
D000077:Acetabulum / Q000503:physiopathology*; D003198:Computer Simulation; D019544:Equipment Failure Analysis; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology* / Q000517:prevention & control*; D008954:Models, Biological; D011474:Prosthesis Design