title: Association of catastrophic biaxial fracture of the proximal sesamoid bones with bony changes of the metacarpophalangeal joint identified by standing magnetic resonance imaging in cadaveric forelimbs of Thoroughbred racehorses.
abstract: OBJECTIVE
  To compare bony changes in the metacarpophalangeal joint (MCPJ) of racehorses with (cases) and without (controls) biaxial proximal sesamoid bone (PSB) fracture as determined by 2 grading scales applied to images of cadaveric forelimbs obtained by means of standing MRI (sMRI).
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Forelimbs from 74 Thoroughbred racehorses (21 cases and 53 controls) that were euthanized at a Florida racetrack.
  
  
  METHODS
  Both forelimbs were harvested from cases and controls. Each forelimb underwent sMRI to obtain images of the MCPJ. Two grading scales were described and used for image evaluation; one assessed the density of the PSBs, and the other assessed the integrity of the subchondral bone (SCB) plate at the distopalmar aspect of the third metacarpal bone (MC3). Logistic regression was used to compare the grades between case and control limbs.
  
  
  RESULTS
  Biaxial PSB fracture was associated with a total PSB grade (sum of lateral and medial PSB grades) ≥ 5 for the fractured limb, total MC3 SCB grade (sum of lateral and medial MC3 SCB grades) ≥ 5 for the contralateral limb, and the presence of orthopedic disease in the contralateral MC3.
  
  
  CONCLUSIONS
  For cases with biaxial PSB fracture, the density of the PSBs in the affected limb was greater and the MC3 of the contralateral limb was more likely to have orthopedic disease, compared with those for controls. Further evaluation of sMRI as a screening tool for identification of racehorses at risk of biaxial PSB fracture is warranted.
authors.affiliation: Equine Medical Center of Ocala, 7107 W Hwy 326, Ocala, FL 34482.
authors.forename: John G
authors.initials: JG
authors.lastname: Peloso
authors.forename: James B
authors.initials: JB
authors.lastname: Vogler
authors.forename: Noah D
authors.initials: ND
authors.lastname: Cohen
authors.forename: Patricia
authors.initials: P
authors.lastname: Marquis
authors.forename: Lynn
authors.initials: L
authors.lastname: Hilt
mesh_terms: D000818:Animals; D016723:Bone Remodeling; D002102:Cadaver; D016022:Case-Control Studies; D037901:Euthanasia, Animal; D005552:Forelimb / Q000473:pathology*; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000473:pathology / Q000662:veterinary*; D006734:Horse Diseases / Q000000981:diagnostic imaging / Q000473:pathology; D006736:Horses / Q000293:injuries*; D008279:Magnetic Resonance Imaging / Q000662:veterinary*; D008663:Metacarpus / Q000000981:diagnostic imaging* / Q000473:pathology; D011859:Radiography; D012420:Running; D012716:Sesamoid Bones / Q000000981:diagnostic imaging* / Q000473:pathology