Comparison of radiography and computed tomography for identification of third metacarpal structural change and associated assessment of condylar stress fracture risk in Thoroughbred racehorses.
Authors: Irandoust Soroush, O'Neil Linnea M, Stevenson Christina M, Franseen Faith M, Ramzan Pieter H L, Powell Sarah E, Brounts Sabrina H, Loeber Samantha J, Ergun David L, Whitton R Chris, Henak Corinne R, Muir Peter
Journal: Equine veterinary journal
Summary
# Editorial Summary Condylar stress fractures of the third metacarpal bone remain a significant cause of catastrophic injury in racing Thoroughbreds, yet early detection through radiographic screening is inconsistent. This controlled ex vivo study compared the diagnostic performance of standard digital radiography and standing computed tomography (sCT) in identifying structural changes within the metacarpophalangeal joint of 31 Thoroughbreds, using direct macroscopic examination and sCT imaging as the reference standard. Digital radiography demonstrated poor sensitivity for detecting subchondral bone changes and lucencies in the condyles and parasagittal grooves—findings that correlated weakly with reference assessments (correlation coefficients below 0.5)—whilst standing sCT performed substantially better with correlation coefficients of 0.49–0.82 and notably improved sensitivity when identifying horses at elevated or high risk of fracture. Critically, observers using both imaging modalities tended to underestimate fracture risk in high-risk cases, suggesting that current screening protocols may miss horses that warrant intervention; however, sCT showed significantly superior repeatability and inter-observer reliability compared with radiography. These findings support the integration of standing sCT into pre-racing screening programmes for horses with questionable radiographic findings, particularly when identifying early degenerative changes that might predict injury risk, though practitioners should remain cautious about false-negative assessments using radiography alone.
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Practical Takeaways
- •Digital radiography alone underestimates condylar stress fracture risk in many cases—consider standing CT for high-risk racehorses in screening programs to improve injury prevention
- •Both imaging modalities tend to underestimate risk in horses with actual structural damage, so clinical judgment and further investigation are warranted when radiographic findings suggest any abnormality
- •Standing CT provides more consistent and reliable assessment across different evaluators, making it more suitable for standardized screening protocols in racing operations
Key Findings
- •Standing CT showed improved sensitivity for detecting subchondral structural changes compared to digital radiography (correlation coefficients 0.49-0.82 vs below 0.5)
- •Sensitivity for condylar stress fracture risk assessment was consistently lower than specificity for both imaging methods across all observers
- •Standing CT demonstrated improved diagnostic sensitivity for risk assessment, particularly for horses categorized as having elevated injury risk on reference assessment
- •Observer assessment repeatability and reliability was significantly better with standing CT than digital radiography