Computed Tomographic Evaluation of the Sagittal Ridge of the Third Metacarpal Bone in Young Thoroughbred Racehorses: A Longitudinal Study.
Authors: Boros Koppány, Dyson Sue, Kovács Ágnes, Lang Zsolt, Nagy Annamaria
Journal: Animals : an open access journal from MDPI
Summary
Understanding changes to the sagittal ridge of the third metacarpal bone is clinically important because radiological abnormalities in this region correlate with metacarpophalangeal joint effusion and reduced performance value in racehorses, yet little is known about their natural progression during early training. This longitudinal computed tomographic study tracked 40 Thoroughbred yearlings at three time points over approximately one year, with 23 horses completing all assessments, measuring bone mineral density via Hounsfield Units across eight radial segments and characterising any hypoattenuating (low-density) lesions by location, size and morphology. Between the first and second examinations (approximately six months into training), mean bone density increased significantly across the sagittal ridge, then plateaued by the third assessment; notably, hypoattenuating lesions decreased in prevalence from 41.3% of limbs at baseline to 30.4% by the final examination, with many lesions either reducing in size or resolving completely. All identified lesions were located in the dorsodistal aspect of the sagittal ridge, most commonly presenting as proximodistally elongated defects or those extending into the trabecular bone beneath the cortical surface. Most significantly for practice, none of these hypoattenuating lesions were associated with clinical lameness in this cohort, and their tendency to improve with early training suggests they may represent adaptive bone remodelling rather than pathological lesions requiring intervention—though these findings warrant validation in horses with concurrent clinical signs or poor performance outcomes.
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Practical Takeaways
- •Sagittal ridge lesions visible on CT imaging in young racehorses may resolve or improve during the first 12 months of training without causing clinical lameness, suggesting these findings warrant cautious rather than alarmist interpretation.
- •The dorsodistal location of sagittal ridge lesions is consistent; practitioners should focus preventive or monitoring efforts on this specific region.
- •Early radiological abnormalities do not necessarily predict lameness or poor performance, so decisions regarding sales, training intensity, or therapeutic intervention should not be made solely on CT findings without clinical correlation.
Key Findings
- •Mean Hounsfield Unit values of the sagittal ridge increased between time 0 and time 1 (first six months), then plateaued at time 2.
- •Hypoattenuating lesions decreased in prevalence from 41.3% of limbs at time 0 to 30.4% at time 2, with lesions capable of resolving during early training.
- •All hypoattenuating lesions were located in the dorsodistal aspect of the sagittal ridge, with elongated proximodistal orientation being the most common shape.
- •Hypoattenuating lesions in this population were not associated with lameness during the study period.