title: Photoelastic stress analysis of strain patterns in equine hooves after four-point trimming.
abstract: OBJECTIVE
  To evaluate changes in strain patterns in normal equine hooves following 4-point trimming, using photoelastic stress analysis.
  
  
  METHODS
  15 equine front limbs with normal hoof configuration.
  
  
  METHODS
  Limbs were disarticulated at the carpometacarpal joint. Weight-bearing surfaces of each hoof were trimmed level to ensure 100% ground contact. Hoof walls were coated with a custom-made strain-sensitive plastic, and limbs were loaded to a third of body weight. Using a polariscope, strain distribution, magnitudes, and directions were evaluated in level hooves as well as before and after standardized 4-point trimming. Repeated-measures ANOVA was used to compare strain magnitudes and directions before and after trimming.
  
  
  RESULTS
  In leveled specimens, strain fields were symmetrically distributed above the heels and at quarter-toe junctions along a line between the middle and distal thirds of the hoof wall. After 4-point trimming, strain epicenters localized above the contact points, whereas strain magnitudes significantly increased by approximately 50%. Decreasing contact area by 50% resulted in an additional significant increase (32%) in strain magnitude. Trimming did not have a significant effect on strain orientations.
  
  
  CONCLUSIONS
  This study documents that 4-point trimming results in strain concentration above the hoof contact points and that strain magnitude is dependent on contact area.
authors.affiliation: Laboratory for Comparative Orthopaedic Research, Michigan State University, East Lansing 48824, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Dejardin
authors.forename: S P
authors.initials: SP
authors.lastname: Arnoczky
authors.forename: G L
authors.initials: GL
authors.lastname: Cloud
authors.forename: J A
authors.initials: JA
authors.lastname: Stick
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004548:Elasticity; D005552:Forelimb; D006724:Hoof and Claw / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D013180:Sprains and Strains