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Strain distribution in the proximal human femur during in vitro simulated sideways fall

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Author

  • Lorenzo Zani
  • Paolo Erani
  • Lorenzo Grassi
  • Fulvia Taddei
  • Luca Cristofolini

Summary, in English

This study assessed: (i) how the magnitude and direction of principal strains vary for different sideways fall loading directions; (ii) how the principal strains for a sideways fall differ from physiological loading directions; (iii) the fracture mechanism during a sideways fall. Eleven human femurs were instrumented with 16 triaxial strain gauges each. The femurs were non-destructively subjected to: (a) six loading configurations covering the range of physiological loading directions; (b) twelve configurations simulating sideways falls. The femurs were eventually fractured in a sideways fall configuration while high-speed cameras recorded the event. When the same force magnitude was applied, strains were significantly larger in a sideways fall than for physiological loading directions (principal compressive strain was 70% larger in a sideways fall). Also the compressive-to-tensile strain ratio was different: for physiological loading the largest compressive strain was only 30% larger than the largest tensile strain; but for the sideways fall, compressive strains were twice as large as the tensile strains. Principal strains during a sideways fall were nearly perpendicular to the direction of principal strains for physiological loading. In the most critical regions (medial part of the head-neck) the direction of principal strain varied by less than 9° between the different physiological loading conditions, whereas it varied by up to 17° between the sideways fall loading conditions. This was associated with a specific fracture mechanism during sideways fall, where failure initiated on the superior-lateral side (compression) followed by later failure of the medially (tension), often exhibiting a two-peak force-displacement curve.

Publishing year

2015

Language

English

Pages

2130-2143

Publication/Series

Journal of Biomechanics

Volume

48

Issue

10

Document type

Journal article

Publisher

Elsevier

Topic

  • Medical Engineering

Keywords

  • Hip fractures
  • Sideways fall
  • Physiological loading
  • Strain distribution
  • Direction of principal strain
  • Structural optimization

Status

Published

ISBN/ISSN/Other

  • ISSN: 1873-2380