Detection of Articular Pathology of the Distal Aspect of the Third Metacarpal Bone in Thoroughbred Racehorses: Comparison of Radiography, Computed Tomography and Magnetic Resonance Imaging

Authors: 
Thomas O'Brien, Theresa A. Baker, Sabrina H. Brounts, Susannah J. Sample, Mark D. Markel, Mary C. Scollay, Patricia Marquis and Peter Muir
Volume: 
40
Number: 
8
Pages: 
942-951
Journal: 
Veterinary Surgery
Date: 
December 2011

To compare digital radiography (DR), computed tomography (CT), and magnetic resonance imaging (MRI) for detection of pathology of the distal aspect of the third metacarpal bone (MC3) and to assess whether arthrography would improve detection of articular cartilage or subchondral bone cracking.
Study Design
Cross-sectional study.
Sample Population
Limb specimens from 17 Thoroughbred horses after catastrophic injury and 4 age-matched control horses.
Methods
Standard DR, CT, and MRI images of the metacarpophalangeal joint were acquired before and after iohexol injection. Pathologic features detected with imaging and on visual inspection of cartilage and subchondral bone of the distal aspect of MC3 were graded. Imaging observations were compared with pathologic abnormalities.
Results
Inspection revealed obvious changes in the cartilage and subchondral bone surfaces in Thoroughbreds. Both CT and MRI were superior to DR for detection of subchondral bone pathology. Cracking of cartilage was not detected by any imaging modality. Signal changes associated with cartilage loss and development of repair tissue were evident on MRI in 9/19 cases. There was significant correlation (P < .05) between subchondral bone pathology detected on both CT and MRI, and cartilage pathology on gross examination. Contrast arthrography did not improve the detection of articular cartilage or subchondral plate cracking.
Conclusion
Both CT and MRI are superior to DR for detection of subchondral bone pathology, but underestimate the extent of joint adaptation and pathologic damage. MRI was able to detect cartilage degeneration.