title: Effect of hoof angle on joint contact area in the equine metacarpophalangeal joint following simulated impact loading ex vivo.
abstract: BACKGROUND
  To add to the existing data on impact loading of the metacarpophalangeal (MCP) joint as a precursor to assessing the potential role of impact in joint disease.
  
  
  OBJECTIVE
  To examine the effect of impact loading on contact areas of the first phalanx (P1) and proximal sesamoids (PS) with the third metacarpal (McIII) under 3 hoof-strike conditions (toe-first, flat, heel-first).
  
  
  METHODS
  Randomised, repeated controlled experiment using cadaver material.
  
  
  METHODS
  Eight cadaver limbs were subjected to randomised, repeated controlled trials where the hoof was struck by a pendulum impact machine (impact velocity 3.55 m/s) under 3 strike conditions. Data from pressure sensitive film placed over medial and lateral McIII condyles and lateromedially across the dorsal aspect of McIII were quantified: total areas of P1 and PS contact (cm(2) ) at maximum recorded pressure; centroid locations of contact areas relative to the sagittal ridge (cm) and transverse ridge (cm) and dispersion of pixels (cm(4) ) for each McIII condyle (medial/lateral). The effect of the strike conditions on each variable were statistically tested using repeated-measures ANOVA (α = 0.05).
  
  
  RESULTS
  Contact area between P1 and McIII condyles fell in well-defined areas bounded by the sagittal and transverse ridge, contact areas from PS were smaller and widely dispersed across McIII palmar border. Ratio of contact area of P1 to PS was 2.83 (P<0001). Hoof strike had no significant effect on contact area (P>0.54) CONCLUSIONS: Contact at impact (primarily from P1 and distally situated on McIII), contrasts with contact areas at midstance from both P1 and PS, symmetrically placed. Under impact, the greatest contact area was on the dorsal aspect of the medial condyle and coincides with the area subjected to the greatest increase in subchondral bone stiffening in joint disease.
authors.affiliation: Department of Biomedical Science, University of Guelph, Ontario, Canada.
authors.forename: C A
authors.initials: CA
authors.lastname: McCarty
authors.affiliation: Department of Biomedical Science, University of Guelph, Ontario, Canada.
authors.forename: J J
authors.initials: JJ
authors.lastname: Thomason
authors.affiliation: Department of Biomedical Engineering, School of Engineering, University of Guelph, Ontario, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Gordon
authors.affiliation: Department of Clinical Studies, University of Guelph, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Hurtig
authors.affiliation: Department of Biomedical Science, University of Guelph, Ontario, Canada.
authors.forename: W
authors.initials: W
authors.lastname: Bignell
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002102:Cadaver; D006724:Hoof and Claw / Q000033:anatomy & histology*; D006736:Horses / Q000502:physiology*; D007596:Joints / Q000502:physiology*; D011312:Pressure
keywords: biomechanics; horse; impact; joint loading; metacarpophalangeal; osteoarthritis