Imaging and Gross Pathological Appearance of Changes in the Parasagittal Grooves of Thoroughbred Racehorses.
Authors: Johnston Georgina C A, Ahern Benjamin J, Palmieri Chiara, Young Alex C
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Parasagittal Groove Changes in Thoroughbred Racehorses Understanding what constitutes normal adaptive change versus early fracture risk in the equine fetlock remains challenging for practitioners managing racing Thoroughbreds, which prompted Johnston and colleagues to systematically compare imaging findings with gross pathological specimens from twenty deceased racing and training horses. Using radiography, low-field MRI, CT, contrast arthrography and post-mortem examination, the researchers mapped parasagittal groove (PSG) changes across all fetlocks and correlated imaging appearances with documented fracture status. Horses that had sustained fetlock fractures showed significantly higher prevalence of lateromedial PSG sclerosis asymmetry and lateral PSG lysis compared to fracture-free controls—findings that suggest these changes may reflect microdamage accumulation rather than innocent adaptive remodelling. Importantly, standard radiography proved poor at detecting PSG pathology, MRI poorly visualised PSG lysis, and subchondral bone defects were difficult to distinguish from cartilage involvement, whilst the clinical significance of STIR hyperintensity remains unresolved. For equine practitioners, these findings advocate bilateral advanced imaging (CT or high-field MRI) when investigating suspected fetlock disease in racing stock, with particular attention to asymmetrical sclerosis and lytic changes as potential indicators of fracture risk rather than normal training adaptation.
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Practical Takeaways
- •When evaluating racing Thoroughbreds with suspected fetlock problems, use CT or contrast arthrography rather than radiography alone, as these modalities better detect PSG changes associated with fracture risk
- •Asymmetric sclerosis or lysis in the parasagittal grooves may indicate microdamage accumulation and increased fracture risk—bilateral advanced imaging is recommended to identify these subtle changes
- •Not all PSG changes indicate pathology; some represent normal adaptive remodeling from galloping, so imaging findings must be interpreted carefully alongside clinical signs
Key Findings
- •Lateromedial PSG sclerosis asymmetry and lateral PSG lysis were more prevalent in horses with fetlock fractures compared to non-fractured horses
- •PSG lysis was not readily detected using MRI despite being visible on CT and gross pathology
- •Radiography was poor for detecting PSG changes; CT and contrast arthrography proved more useful imaging modalities
- •PSG subchondral bone defects and STIR hyperintensity were not reliably associated with fracture risk or pathology