Torsional strength reduction due to cortical defects in bone

Bradley C. Edgerton, Kai‐Nan ‐N An, Bernard F. Morrey

Research output: Contribution to journalArticlepeer-review

119 Scopus citations


This study correlated torsional strength reduction with circular defect size in cortical bone, to define the “stress riser” and “open‐section” effect of the defects. The experimental model was developed and verified. Circular defects from 10 to 60% of bone diameter were then created in paired sheep femora and the bones loaded to failure. Contrary to theory, this experimental study suggests that small defects (10%) of bone diameter cause no significant torsional strength reduction. A 20% defect caused a 34% decrease in strength, representing the “stress riser” dimension. Defects between 20 and 60% of bone diameter decreased strength linearly as a function of defect size, and thus no discrete “open section” dimension was identified. For circular defects we were unable to demonstrate a discrete “open section” effect at which dramatic strength reduction is observed. These data may prove to be helpful when planning surgery that involves placing defects in bone such as for infection, biopsy, and prosthesis removal. The accepted guideline to avoid defects of greater than 50% of the bone diameter may be too great. Our data reveal this 62% reduction in torque strength and 88% energy to failure exist with a 50% circular defect.

Original languageEnglish (US)
Pages (from-to)851-855
Number of pages5
JournalJournal of Orthopaedic Research
Issue number6
StatePublished - Nov 1990


  • Circular defect
  • Cortical bone
  • Torsional strength

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine


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