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Objective

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.