Abstract
Based on numerous national registries, cemented hip replacements have globally better long-term results than uncemented hip replacements. For example, following data have been published in national registries:
These registries demonstrated clearly that cemented fixation should be definitively preferred than uncemented fixation… Despite this evidence, uncemented fixation is more and more used in the majority of the countries performing total hip replacements.
A recent paper analysed the Swedish situation and may give some reasons for explaining this paradox. A Cox proportional hazards model was used to analyze the Relative Risk (RR) of revision for different type of implants and/or fixation for 170,413 total hip arthroplasties. The RR was adjusted for sex, age, and underlying diagnosis. If the RR is lower than 1, less revisions are seen with uncemented fixation and less revisions are seen with cemented fixation when the RR is higher than 1. The figure 1 summarizes the table 6 of this publication.
This figure naturally confirms that globally cemented fixation has a lower revision burden with an adjusted RR of 1.5 (revision of any component for aseptic loosening) than uncemented fixation. This difference in the revision is controlled by the cups, where the adjusted RR for uncemented cups is 1.8. Stems demonstrate an opposite behaviour with a lower revision burden for uncemented fixation with an adjusted RR of 0.4.
Analysing the revision rate of the 5 most common implants (cemented versus uncemented), the adjusted RR for aseptic loosening is lower than 1 for both cups and stems. The difference of the RR between all cups (RR: 1.8) and the 5 most common cups (RR: 0.5) indicates undeniably that some cup have a major influence on the revision rate of uncemented systems.
This analysis allows to draw following conclusions:
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In national registries, cemented fixation is globally superior.
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The lower clinical results of uncemented fixation seem to be controlled by badly designed uncemented implants.
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Modern uncemented implants have as least equivalent results than cemented implants.
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Based on these results, uncemented fixation will be the key fixation for this century.
