Evaluation of a testing method for the fatigue performance of total knee tibial trays

S. P. Ahir, G. W. Blunn, H. Haider, P. S. Walker

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Catastrophic failure of tibial baseplates due to fatigue fracture have occurred in patients. The International Standards Organisation (ISO) have proposed an endurance test to ensure a safety level for trays with respect to this problem. At present the magnitude of the applied load has not been defined. The purpose of this study is to evaluate the ISO test by comparing the results of two tibial trays: one with a clinical history of fracture of the tibial baseplate in some cases (Kinematic) and one without such a record (Kinemax). A load of 2000N was selected, representing the peak force during the normal walking cycle. Finite element analysis (FEA) predicted that both the Kinematic and Kinemax trays would rapidly fail for two defined contact positions. Mechanical testing performed on both these components confirmed the FEA predictions. However, under service conditions, the Kinematic tray has been reported to have a failure of only 1-2%, the failure occurring at a mean of 54 months for early fracture and 7 years for late fracture. There are no published reports of failed Kinemax trays. It is concluded that the ISO test is an exaggeration of reality when a physiological load is used. As a result of our study we propose that a load of 500N would effectively screen components with respect to the ISO test conditions for the likelihood of fracture. Copyright (C) 1999 Elsevier Science Ltd.

Original languageEnglish (US)
Pages (from-to)1049-1057
Number of pages9
JournalJournal of Biomechanics
Issue number10
StatePublished - Oct 1999
Externally publishedYes


  • Finite element analysis
  • Fracture
  • Knee replacement
  • Testing methods
  • Tibial tray

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine
  • Biomedical Engineering
  • Rehabilitation


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