AI Article Synopsis
- Initial stability is crucial for successful osseointegration of press-fit acetabular cups in hip replacements, which is often not accurately assessed in current in vitro methods.
- The study explored how bone density and acetabular shape impact cup stability using a new technique to measure micromotion under realistic loading conditions.
- Results showed that lower bone density, such as in osteoporotic cases, leads to increased micromotion and a higher risk of cup loosening, highlighting the limitations of simplified models in evaluating cup stability.
Article Abstract
Initial stability is an essential prerequisite to achieve osseointegration of press-fit acetabular cups in total hip replacements. Most in vitro methods that assess cup stability do not reproduce physiological loading conditions and use simplified acetabular models with a spherical cavity. The aim of this study was to investigate the effect of bone density and acetabular geometry on cup stability using a novel method for measuring acetabular cup micromotion. A press-fit cup was inserted into Sawbones(®) foam blocks having different densities to simulate normal and osteoporotic bone variations and different acetabular geometries. The stability of the cup was assessed in two ways: (a) measurement of micromotion of the cup in 6 degrees of freedom under physiological loading and (b) uniaxial push-out tests. The results indicate that changes in bone substrate density and acetabular geometry affect the stability of press-fit acetabular cups. They also suggest that cups implanted into weaker, for example, osteoporotic, bone are subjected to higher levels of micromotion and are therefore more prone to loosening. The decrease in stability of the cup in the physiological model suggests that using simplified spherical cavities to model the acetabulum over-estimates the initial stability of press-fit cups. This novel testing method should provide the basis for a more representative protocol for future pre-clinical evaluation of new acetabular cup designs.
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| http://dx.doi.org/10.1177/0954411914557714 | DOI Listing |
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