title: Resistance of equine tibiae and radii to side impact loads.
abstract: BACKGROUND
  There are no detailed studies describing the resistance of equine tibiae and radii to side impact loads, such as a horse kick and a better understanding of the general long bone impact behavioural model is required.
  
  
  OBJECTIVE
  To quantify the typical impact energy required to fracture or fissure an equine long bone, as well as to determine the range and time course of the impact force under conditions similar to that of a horse kick.
  
  
  METHODS
  Seventy-two equine tibiae and radii were investigated using a drop impact tester. The prepared bones were preloaded with an axial force of 2.5 kN and were then hit in the middle of the medial side. The impact velocity of the metal impactor, weighting 2 kg, was varied within the range of 6-11 m/s. The impact process was captured with a high-speed camera from the craniomedial side of the bone. The videos were used both for slow-motion observation of the process and for quantifying physical parameters, such as peak force via offline video tracking and subsequent numerical derivation of the 'position vs. time' function for the impactor.
  
  
  RESULTS
  The macroscopic appearance of the resultant bone injuries was found to be similar to those produced by authentic horse kicks, indicating a successful simulation of the real load case. The impact behaviours of tibiae and radii do not differ considerably in terms of the investigated general characteristics. Peak force occurred between 0.15-0.30 ms after the start of the impact. The maximum contact force correlated with the 1.45-power of the impact velocity if no fracture occurred (F(max) ≈ 0.926 · v(i) (1.45) ). Peak force scatter was considerably larger within the fractured sub-group compared with fissured bones. The peak force for fracture tended to lie below the aforementioned function, within the range of F(max) = 11-23 kN ('fracture load'). The impact energy required to fracture a bone varied from 40-90 J.
  
  
  CONCLUSIONS
  The video-based measuring method allowed quantifying of the most relevant physical parameters, such as contact force and energy balance.
  
  
  CONCLUSIONS
  The results obtained should help with the development of bone implants and guards, supporting theoretical studies, and in the evaluation of bone injuries.
authors.affiliation: Swiss Federal Laboratories for Materials Testing and Research (Empa), Dübendorf, Switzerland. gabor.piskoty@empa.ch
authors.forename: G
authors.initials: G
authors.lastname: Piskoty
authors.forename: S
authors.initials: S
authors.lastname: Jäggin
authors.forename: S A
authors.initials: SA
authors.lastname: Michel
authors.forename: B
authors.initials: B
authors.lastname: Weisse
authors.forename: G P
authors.initials: GP
authors.lastname: Terrasi
authors.forename: A
authors.initials: A
authors.lastname: Fürst
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000502:physiology*; D006736:Horses; D011884:Radius / Q000502:physiology*; D013314:Stress, Mechanical; D013977:Tibia / Q000502:physiology*