Abstract
Objective. To determine the load transfer patterns of femurs in the intact, immediate post-operative
and long-term (remodelled) post-operative implanted conditions for Lubinus SPII and
Müller-Curved cemented hip prostheses, and to examine to what extent remodelling may
influence the long-term outcome.
Design. Experimental and finite element (FE) methods were applied to composite femurs under
loads representing the heel-strike phase of gait, determining cortical bone and cement
strains for the different femur conditions.
Background. The authors previously developed protocols to measure bone and cement strains, and
to produce remodelled femur specimens, yet these have not been applied together to
compare strain patterns of different femur conditions. The Lubinus SPII is clinically
more successful than the Müller-Curved stem, with failure mainly due to aseptic loosening.
Methods. Cortical bone strains were determined in intact femurs. Six femurs each were implanted
with the two stem types and cortical bone and cement strains were measured. Bone remodelling
was recreated using a validated CAD–CAM procedure to remove a layer of proximal cortical
bone, replicating a typical scenario found in stable clinical retrievals. Strains
were remeasured. FE methods were used to compliment the experiments.
Results. Stress shielding was reduced with remodelling, though bone strains did not return
to their intact values, particularly around the calcar. Cement strains increased with
remodelling. Differences occurred between the two stems; the Müller-Curved produced
a more severe strain transition.
Conclusions. Procedures were successfully combined together to investigate in vitro the performance
of two cemented stems, in immediate and long-term post-operative conditions. The increase
of cement strains with remodelling is a potential indicator for in vivo cement failure.Relevance
The consequences of femoral bone remodelling on the long-term success of joint replacements
are not well understood, where remodelling may lead to increased bone and cement stresses.
Keywords
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Article info
Publication history
Accepted:
March 25,
2003
Received:
December 12,
2001
Identification
Copyright
© 2003 Elsevier Science Ltd. Published by Elsevier Inc. All rights reserved.
