In-vitro method for assessing femoral implant-bone micromotions in resurfacing hip implants under different loading conditions

L. Cristofolini, E. Varini, M. Viceconti

Research output: Contribution to journalArticlepeer-review

Abstract

Although prosthesis-bone micromotion is known to influence the stability of total hip replacement, no protocol exists to investigate resurfacing hip implants. An in-vitro protocol was developed to measure prosthesis-bone micromot Ions of resurfaced femurs. In order to assess the effect of all loading directions, the protocol included a variety of in-vitro loading scenarios covering the range of directions spanned by the hip resultant force in the most typical motor tasks. Gap-opening and shear-slippage micromotions were measured in the locations where they reach the maximum value. The applicability of the protocol was assessed on two commercial designs and different head sizes. Intra-specimen repeatability and inter-specimen reproducibility were excellent (comparable with the best protocols for cemented hip stems). Results showed that the protocol is accurate enough to detect prosthesis-bone micromotions of the order of a few microns. Statistically significant differences were observed in relation to the direction of the applied force. Using the whole range of hip loads enabled detection of maximum micromotions for any design (the peak value could be different for different loading directions). Application of the protocol during a test to failure indicated that the system could track micromotion up to the last instant prior to failure. The protocol proposed is thus completely validated and can be applied for preliminary screening of new epiphyseal designs.

Original languageEnglish
Pages (from-to)943-950
Number of pages8
JournalProceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
Volume221
Issue number8
DOIs
Publication statusPublished - 2007

Keywords

  • Hip replacement
  • Implant primary stability
  • Implant-femur micromotion
  • Preclinical in-vitro testing
  • Resurfacing epiphyseal prosthesis

ASJC Scopus subject areas

  • Biomedical Engineering
  • Mechanical Engineering
  • Medicine(all)

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