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In vitro comparison of the effects of rough and polished stem surface finish on pressure generation in cemented hip arthroplasty.

Bartlett GE, Beard DJ, Murray DW, Gill HS - Acta Orthop (2009)

Bottom Line: We compared the pressures generated by rough and polished tapered stems at their cement interfaces, in an in vitro model, before and after 1 million load cycles.At the start of the study, the loading of both polished and rough stems generated interface pressures that were not statistically significantly different.The rough stems also migrated distally and wore the cement mantle, leading to increased rotational instability.

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Affiliation: OOEC, Nuffield Department of Orthopaedic Surgery, University of Oxford, Oxford, UK.

ABSTRACT

Background and purpose: High pressures around implants can cause bone lysis and loosening. We investigated how pressures are generated around cemented femoral stems.

Method: We compared the pressures generated by rough and polished tapered stems at their cement interfaces, in an in vitro model, before and after 1 million load cycles.

Results: At the start of the study, the loading of both polished and rough stems generated interface pressures that were not statistically significantly different. After 1 million load cycles, the rough stems generated greater interface pressures than at the start (p = 0.03), with maximum pressure wave amplitudes of 450,000 Pa or 3,375 mm Hg. The pressures generated by polished stems were similar before and after 1 million load cycles, and were lower than the pressures generated by the rough stems (p = 0.01). Stem loading caused micromotion between the stem and cement. Polished stems migrated distally in the cement but retained rotational and axial stability. The rough stems also migrated distally and wore the cement mantle, leading to increased rotational instability.

Interpretation: The change in the rotational micromotion of the rough stem is likely to be the principal cause of the increased stem pump output and to be a key factor in the longevity of cemented femoral implants.

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Related in: MedlinePlus

Cross-sectional view of HAPS apparatus with model stem in situ and showing sampling sites at the cement mantle-stem interface.
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Figure 0001: Cross-sectional view of HAPS apparatus with model stem in situ and showing sampling sites at the cement mantle-stem interface.

Mentions: We assessed the in vitro performance of two groups of model Exeter type stems with either rough or polished surface finishes. Both groups were loaded physiologically for 1 million cycles and the interface pressures were measured at the start and at the end of the loading. The study was performed using the Hip Arthroplasty Pressure Simulator (HAPS) previously reported to be a reliable and reproducible in vitro model of stem pumping (Bartlett et al. 2008) (Figure 1).


In vitro comparison of the effects of rough and polished stem surface finish on pressure generation in cemented hip arthroplasty.

Bartlett GE, Beard DJ, Murray DW, Gill HS - Acta Orthop (2009)

Cross-sectional view of HAPS apparatus with model stem in situ and showing sampling sites at the cement mantle-stem interface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2823172&req=5

Figure 0001: Cross-sectional view of HAPS apparatus with model stem in situ and showing sampling sites at the cement mantle-stem interface.
Mentions: We assessed the in vitro performance of two groups of model Exeter type stems with either rough or polished surface finishes. Both groups were loaded physiologically for 1 million cycles and the interface pressures were measured at the start and at the end of the loading. The study was performed using the Hip Arthroplasty Pressure Simulator (HAPS) previously reported to be a reliable and reproducible in vitro model of stem pumping (Bartlett et al. 2008) (Figure 1).

Bottom Line: We compared the pressures generated by rough and polished tapered stems at their cement interfaces, in an in vitro model, before and after 1 million load cycles.At the start of the study, the loading of both polished and rough stems generated interface pressures that were not statistically significantly different.The rough stems also migrated distally and wore the cement mantle, leading to increased rotational instability.

View Article: PubMed Central - PubMed

Affiliation: OOEC, Nuffield Department of Orthopaedic Surgery, University of Oxford, Oxford, UK.

ABSTRACT

Background and purpose: High pressures around implants can cause bone lysis and loosening. We investigated how pressures are generated around cemented femoral stems.

Method: We compared the pressures generated by rough and polished tapered stems at their cement interfaces, in an in vitro model, before and after 1 million load cycles.

Results: At the start of the study, the loading of both polished and rough stems generated interface pressures that were not statistically significantly different. After 1 million load cycles, the rough stems generated greater interface pressures than at the start (p = 0.03), with maximum pressure wave amplitudes of 450,000 Pa or 3,375 mm Hg. The pressures generated by polished stems were similar before and after 1 million load cycles, and were lower than the pressures generated by the rough stems (p = 0.01). Stem loading caused micromotion between the stem and cement. Polished stems migrated distally in the cement but retained rotational and axial stability. The rough stems also migrated distally and wore the cement mantle, leading to increased rotational instability.

Interpretation: The change in the rotational micromotion of the rough stem is likely to be the principal cause of the increased stem pump output and to be a key factor in the longevity of cemented femoral implants.

Show MeSH
Related in: MedlinePlus