Histological and Histopathological Features of the Third Metacarpal/Tarsal Parasagittal Groove and Proximal Phalanx Sagittal Groove in Thoroughbred Horses with Racing History.
Authors: Lin Szu-Ting, Foote Alastair K, Bolas Nicholas M, Sargan David R, Murray Rachel C
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Structural damage within the sagittal grooves of the distal cannon bone and proximal phalanx represents a significant but poorly characterised pathology in racing Thoroughbreds, prompting Lin and colleagues to undertake detailed histological analysis of 29 cadaver limbs from nine racehorses with active racing histories. The researchers graded tissue damage across three anatomical regions—hyaline cartilage, calcified cartilage, and subchondral bone with trabecular bone—comparing degeneration between areas with visible fissures versus intact cartilage, and across dorsal, middle, and palmar/plantar zones. Fissure locations exhibited substantially more severe pathology at both the third metacarpal/metatarsal level and proximal phalanx (p < 0.001), with distinct regional patterns: the palmar/plantar aspect of the cannon bone and dorsal aspect of the proximal phalanx showed the most pronounced subchondral bone collapse and fatigue injury. These findings suggest that sagittal groove disease follows predictable mechanical pathways, with weight-bearing stress concentrating damage in specific anatomical zones and establishing a clear histopathological signature of bone fatigue injury that clinicians can now use to refine diagnosis and prognosis in lameness cases. Understanding these regional vulnerability patterns may inform preventative conditioning strategies, guide rehabilitation timelines, and help farriers and veterinarians identify at-risk individuals before catastrophic failure occurs.
Read the full abstract on PubMed
Practical Takeaways
- •Fissures in parasagittal/sagittal grooves are markers of significant underlying bone and cartilage degeneration, suggesting these lesions are late-stage manifestations requiring prompt intervention
- •Location within the groove matters: palmar/plantar MC3/MT3 and dorsal P1 sites show worst pathology, warranting focused diagnostic imaging in these regions during lameness workups
- •Bone fatigue injury is a key pathological mechanism in these groove lesions, suggesting training load management and surface evaluation are important preventive strategies in racehorses
Key Findings
- •Histopathological grades in hyaline cartilage, calcified cartilage, and subchondral bone/trabecular bone were significantly more severe in fissure locations than non-fissure locations in MC3/MT3 parasagittal grooves (p < 0.001)
- •Subchondral bone/trabecular bone grades were significantly more severe in fissure than non-fissure locations in P1 sagittal grooves (p < 0.001)
- •Palmar/plantar aspects of MC3/MT3 parasagittal grooves showed more severe pathology and subchondral collapse than middle aspects (p < 0.001)
- •Dorsal and middle aspects of P1 sagittal grooves demonstrated more severe subchondral bone pathology and collapse than palmar/plantar aspects (p < 0.001)