title: Site-specific adaptive remodeling of Greyhound metacarpal cortical bone subjected to asymmetrical cyclic loading.
abstract: OBJECTIVE
  To quantify geometric, inertial, and histomorphometric properties at the mid-diaphyseal level of left and right metacarpal bones (MCB) of racing Greyhounds.
  
  
  METHODS
  MCB from 7 racing Greyhounds euthanatized for reasons unrelated to MCB abnormalities.
  
  
  METHODS
  Mid-diaphyseal transverse sections of left and right MCB were stained with H&E or microradiographed. Images of stained sections were digitized, and cross-sectional area, cortical area, and maximum and minimum area moments of inertia of each bone were determined. Histomorphometric data (osteonal density, osteonal birefringence, and endosteal new lamellar bone thickness) were collected in 4 quadrants (dorsal, palmar, lateral, medial). Values were compared between limbs and among bones and quadrants.
  
  
  RESULTS
  Cross-sectional area, cortical area, and maximum and minimum moments of inertia of left MCB-IV and -V were significantly greater, compared with contralateral bones. Overall osteonal densities in the dorsal quadrants of left MCB were greater, compared with lateral and medial quadrants. Also, percentage of birefringent osteons was significantly greater in the dorsal quadrant of left MCB-III, -IV, and -V, compared with the palmar quadrant. Thickness of new endosteal lamellar bone was not significantly influenced by limb, bone, or quadrant.
  
  
  CONCLUSIONS
  Increased cortical thickness and geometric properties of left MCB-IV and -V of Greyhounds, together with altered turnover and orientation of osteons in the dorsal quadrants of left MCB, are site-specific adaptive responses associated with asymmetric cyclic loading as a result of racing on circular tracks. Site-specific adaptive remodeling may be important in the etiopathogenesis of fatigue fractures in racing Greyhounds.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus 43210-1089, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Johnson
authors.forename: G A
authors.initials: GA
authors.lastname: Skinner
authors.forename: P
authors.initials: P
authors.lastname: Muir
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D016723:Bone Remodeling / Q000502:physiology*; D004285:Dogs / Q000033:anatomy & histology / Q000502:physiology*; D005552:Forelimb / Q000033:anatomy & histology / Q000502:physiology; D006253:Haversian System / Q000033:anatomy & histology / Q000502:physiology; D006651:Histocytochemistry / Q000662:veterinary; D008663:Metacarpus / Q000033:anatomy & histology / Q000502:physiology*; D018715:Microscopy, Video / Q000662:veterinary