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A new paradigm for the in vitro simulation of sideways fall loading of the proximal femur

Zani, Lorenzo; Cristofolini, Luca; Juszczyk, Mateusz Maria; Grassi, Lorenzo LU and Viceconti, Marco (2014) In Journal of Mechanics in Medicine and Biology 14(01).
Abstract
Although the direction of loads applied to the proximal human femur is unpredictable during sideways fall, most in vitro and numerical simulations refer to a single loading condition (15° internal rotation; 10° adduction), which has been anecdotally suggested in the 1950s. The aim of the present study was to improve in vitro simulations of sideways falls on the proximal femur.



An in vitro setup was developed that allowed exploring a range of loading directions (+/- 90° internal–external rotation; 0°–50° adduction). To enable accurate control of the loading conditions (direction and magnitude of all load components applied to the femur), the setup included a number of low-friction linear and rotary bearings. The setup was... (More)
Although the direction of loads applied to the proximal human femur is unpredictable during sideways fall, most in vitro and numerical simulations refer to a single loading condition (15° internal rotation; 10° adduction), which has been anecdotally suggested in the 1950s. The aim of the present study was to improve in vitro simulations of sideways falls on the proximal femur.



An in vitro setup was developed that allowed exploring a range of loading directions (+/- 90° internal–external rotation; 0°–50° adduction). To enable accurate control of the loading conditions (direction and magnitude of all load components applied to the femur), the setup included a number of low-friction linear and rotary bearings. The setup was instrumented with an axial and a torsional load cell, three displacement transducers and a rotation transducer to monitor the most significant components of load/displacement during testing. The strain distribution was measured on the bone surface (16 triaxial strain gauges, 2,000 Hz). Fracture was recorded with a high-speed camera.



The setup was successfully tested on a cadaveric femur non-destructively (12 loading configurations) and destructively (15° internal rotation; 10° adduction). All measurements were highly repeatable (the displacements of the femoral head varied by < 2% between repetitions; the tilt in the frontal plane by < 0.05°; and strain varied on average 0.34% between repetitions). The displacement of the femoral head varied by over 50% when the same force was applied in different directions. Principal strains at the same location varied by over 70%, depending on the direction of the applied force. The high-speed video enabled the identification of the point of fracture initiation.



This study has shown that a new paradigm for testing the proximal femur (including improved testing conditions and a variety of loading configurations) can provide more accurate and more extensive information about the state of strain. (Less)
Please use this url to cite or link to this publication:
author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
in vitro destructive test, bone strain distribution, sideways fall, proximal femur fracture, Biomechanics
in
Journal of Mechanics in Medicine and Biology
volume
14
issue
01
publisher
World Scientific
external identifiers
  • scopus:84894834644
ISSN
1793-6810
DOI
10.1142/S0219519414500055
language
English
LU publication?
no
id
d43032d4-cdc2-4a3a-8b85-b1cfaa70d4bc (old id 3956963)
date added to LUP
2013-08-02 10:51:43
date last changed
2017-01-01 07:35:00
@article{d43032d4-cdc2-4a3a-8b85-b1cfaa70d4bc,
  abstract     = {Although the direction of loads applied to the proximal human femur is unpredictable during sideways fall, most in vitro and numerical simulations refer to a single loading condition (15° internal rotation; 10° adduction), which has been anecdotally suggested in the 1950s. The aim of the present study was to improve in vitro simulations of sideways falls on the proximal femur.<br/><br>
<br/><br>
An in vitro setup was developed that allowed exploring a range of loading directions (+/- 90° internal–external rotation; 0°–50° adduction). To enable accurate control of the loading conditions (direction and magnitude of all load components applied to the femur), the setup included a number of low-friction linear and rotary bearings. The setup was instrumented with an axial and a torsional load cell, three displacement transducers and a rotation transducer to monitor the most significant components of load/displacement during testing. The strain distribution was measured on the bone surface (16 triaxial strain gauges, 2,000 Hz). Fracture was recorded with a high-speed camera.<br/><br>
<br/><br>
The setup was successfully tested on a cadaveric femur non-destructively (12 loading configurations) and destructively (15° internal rotation; 10° adduction). All measurements were highly repeatable (the displacements of the femoral head varied by &lt; 2% between repetitions; the tilt in the frontal plane by &lt; 0.05°; and strain varied on average 0.34% between repetitions). The displacement of the femoral head varied by over 50% when the same force was applied in different directions. Principal strains at the same location varied by over 70%, depending on the direction of the applied force. The high-speed video enabled the identification of the point of fracture initiation.<br/><br>
<br/><br>
This study has shown that a new paradigm for testing the proximal femur (including improved testing conditions and a variety of loading configurations) can provide more accurate and more extensive information about the state of strain.},
  author       = {Zani, Lorenzo and Cristofolini, Luca and Juszczyk, Mateusz Maria and Grassi, Lorenzo and Viceconti, Marco},
  issn         = {1793-6810},
  keyword      = {in vitro destructive test,bone strain distribution,sideways fall,proximal femur fracture,Biomechanics},
  language     = {eng},
  number       = {01},
  publisher    = {World Scientific},
  series       = {Journal of Mechanics in Medicine and Biology},
  title        = {A new paradigm for the in vitro simulation of sideways fall loading of the proximal femur},
  url          = {http://dx.doi.org/10.1142/S0219519414500055},
  volume       = {14},
  year         = {2014},
}