title: Injury tolerance criteria for short-duration axial impulse loading of the isolated tibia.
abstract: BACKGROUND
  Impulse loading of the lower leg during events such as ejection seat landings or in-vehicle land mine blasts may result in devastating injuries. These impacts achieve higher forces over shorter durations than car crashes, from which experimental results have formed the current basis for protective measures of an axial force limit of 5.4 kN, as registered by an anthropomorphic test device (ATD). The hypotheses of this study were that the injury tolerance of the isolated tibia to short-duration axial loading is higher than that previously reported and that secondary parameters such as momentum or kinetic energy are significant for fracture tolerance, in addition to force.
  
  
  METHODS
  Seven pairs of cadaveric tibias were impacted using a pneumatic testing apparatus, replicating short-duration axial impulse events. One specimen from each pair was impacted with a light mass and the contralateral impacted with a heavy mass, to investigate the effects of momentum and kinetic energy, as well as force, on injury. Impacts were applied incrementally until failure.
  
  
  RESULTS
  Force, kinetic energy, age, and height were shown to be significant factors in the probability of fracture. A 10% risk of injury corresponded to an impact force of 7.9 kN, with an average kinetic energy of 240 J. In comparison, this same impact level applied to an ATD would register a force of 16.2 kN because of the higher stiffness of the ATD.
  
  
  CONCLUSIONS
  These results suggest that the current injury standard may be too conservative for the tibia during high-speed impacts such as in-vehicle land mine blasts and that factors in addition to force should be taken into consideration.
authors.affiliation: The Jack McBain Biomechanical Testing Laboratory, Thompson Engineering Building, Department of Mechanical and Materials Engineering, The University of Western Ontario, London, Ontario, Canada.
authors.forename: Cheryl E
authors.initials: CE
authors.lastname: Quenneville
authors.forename: Stewart D
authors.initials: SD
authors.lastname: McLachlin
authors.forename: Gillian S
authors.initials: GS
authors.lastname: Greeley
authors.forename: Cynthia E
authors.initials: CE
authors.lastname: Dunning
mesh_terms: D000328:Adult; D000367:Age Factors; D001696:Biomechanical Phenomena / Q000502:physiology; D001827:Body Height; D050723:Fractures, Bone / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013314:Stress, Mechanical; D013977:Tibia / Q000293:injuries* / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology