Preclinical assessment of the long-term endurance of cemented hip stems. Part 1: Effect of daily activities - A comparison of two load histories

L. Cristofolini, A. Saponara Teutonico, P. Savigni, P. Erani, M. Viceconti

Research output: Contribution to journalArticlepeer-review

Abstract

The loads during daily activities contribute to fixation failure of cemented hip stems. In-vitro preclinical testing so far has consisted of simulating one or two conditions. Only a small percentage of hip implants fail, with a higher failure rate in most active patients. The goal was to define a procedure to assess the long-term effect of the lifestyle of a reasonably active patient on implant micromotions. Thus, a cyclic load of constant amplitude is unsuitable. All activities inducing high loads were included, to replicate the most critical scenario in terms of fatigue. The following motor tasks were simulated: stair climbing and descending, car entry and exit, bathtub entry and exit, and stumbling. An in-vitro simulation running for 15 days was able to replicate the load peaks occurring in 24 years of patient activity. Inducible micromotion and permanent migration were monitored. The load history was successfully applied to two different designs with known clinical performance, yielding significantly different micromotions for the two types. Results from the present load history were compared against a simpler profile including only stair climbing. Results showed that the new load profile is more sensitive to differences and can more easily discriminate between different designs. Part 2 of this work describes a further validation against retrieved implants.

Original languageEnglish
Pages (from-to)569-584
Number of pages16
JournalProceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
Volume221
Issue number6
DOIs
Publication statusPublished - 2007

Keywords

  • Cemented stem
  • Fatigue testing
  • Hip prostheses
  • Inducible micromotions
  • Long-term stability
  • Permanent migrations
  • Physiological loading
  • Stair climbing

ASJC Scopus subject areas

  • Biomedical Engineering
  • Mechanical Engineering
  • Medicine(all)

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