title: Can high-resolution peripheral quantitative computed tomography imaging of subchondral and cortical bone predict condylar fracture in Thoroughbred racehorses?
abstract: BACKGROUND
  High-resolution 3D imaging may improve the prediction and/or early identification of condylar fractures of the distal metacarpus/tarsus and reduce the frequency of breakdown injury in racehorses.
  
  
  OBJECTIVE
  To test the hypotheses that horses suffering condylar fractures have higher bone volume fraction (BV/TV) of the distal metacarpal epiphysis, greater subchondral bone thickness at the fracture site and higher second moment of inertia in the metacarpal midshaft as identified with high-resolution 3D imaging.
  
  
  METHODS
  Cross-sectional study using cadaver material.
  
  
  METHODS
  Thoroughbreds that died on racetracks were grouped as: 1) horses with third metacarpal (McIII) fractures with a condylar component (cases, n = 13); 2) horses with no limb fracture (controls, n = 8); 3) horses with fractures in other bones or suspensory apparatus disruption (other fatal injuries, n = 16). The palmar condyles of McIII and the midshaft were examined with high resolution peripheral quantitative computed tomography (HR-pQCT). Statistical analysis included logistic regression and Spearman's correlation.
  
  
  RESULTS
  There were no significant differences in BV/TV of distal McIII and second moment of inertia of the midshaft between cases and controls. Epiphyseal bone BV/TV was greater in injured limbs of horses with any fatal limb injury (Groups 1 and 3 combined) compared with controls (odds ratio = 1.20, 95% confidence interval 1.01-1.42, P = 0.034). An epiphyseal BV/TV>0.742 resulted in a sensitivity of 82.8% and specificity of 62.5% in identifying horses with fatal limb injury. In horses without condylar fracture, increased subchondral bone thickness was associated with palmar osteochondral disease lesions in the adjacent condyle (rs = 0.65, P<0.001).
  
  
  CONCLUSIONS
  Increased BV/TV of the distal metacarpus may have some value for identifying horses at risk of any fatal breakdown injury but not metacarpal condylar fractures. Measurement of parasagittal groove subchondral bone thickness is complicated by adjacent palmar osteochondral disease lesions. Thus, high-resolution imaging of the distal metacarpus appears to have limited ability to identify horses at risk of condylar fractures.
authors: Faculty of Veterinary Science, University of Melbourne, Werribee, Victoria, Australia.
authors: G D
authors: http://orcid.org/0000-0002-1153-3772
authors: GD
authors: Trope
authors: Department of Endocrinology and Medicine, Austin Health, University of Melbourne, Parkville, Victoria, Australia.
authors: A
authors: A
authors: Ghasem-Zadeh
authors: Faculty of Veterinary Science, University of Melbourne, Werribee, Victoria, Australia.
authors: G A
authors: GA
authors: Anderson
authors: Faculty of Veterinary Science, University of Melbourne, Werribee, Victoria, Australia.
authors: E J
authors: EJ
authors: Mackie
authors: Faculty of Veterinary Science, University of Melbourne, Werribee, Victoria, Australia.
authors: R C
authors: RC
authors: Whitton
mesh_terms: D000818:Animals; D015519:Bone Density; D002102:Cadaver; D003430:Cross-Sectional Studies; D005260:Female; D005552:Forelimb; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000662:veterinary*; D006734:Horse Diseases / Q000000981:diagnostic imaging*; D006736:Horses; D008297:Male; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000662:veterinary*
keywords: condylar fracture; high-resolution quantitative computed tomography; horse; metacarpal fracture; stress fracture; three-dimensional imaging