Microstructural features of subchondral radiolucent lesions in the medial femoral condyle of juvenile Thoroughbreds: A microcomputed tomography and histological analysis.
Authors: Lemirre Thibeaut, Santschi Elizabeth M, Girard Christiane A, Fogarty Ursula, Janes Jennifer G, Richard Helene, Laverty Sheila
Journal: Equine veterinary journal
Summary
# Editorial Summary Subchondral radiolucent lesions in the medial femoral condyle (MFC) of young Thoroughbreds have an unclear cause, and this 2022 post-mortem investigation examined 178 femurs to determine whether osteochondrosis, the commonly suspected culprit, was actually responsible. Using microcomputed tomography and histological analysis, researchers identified radiolucencies in 19.1% of juveniles (predominantly under 7 months old when positioned axially), then compared their microstructural features against age-matched controls and very young foals without lesions. Strikingly, chondronecrosis—the hallmark of osteochondrosis—was present in only 82.6% of affected horses, and entirely absent in the youngest unaffected foals, suggesting osteochondrosis is not the sole or even necessary cause of these lesions; instead, the consistent finding of osteochondral separation with fibrin deposition and subsequent fibroplasia pointed toward acute traumatic injury followed by healing response. For practitioners managing juvenile Thoroughbreds with radiographic MFC radiolucencies, these findings shift the clinical narrative: rather than assuming developmental osteochondral disease, a trauma-based mechanism should be entertained, which carries different prognostic and management implications for return to training and athletic soundness.
Read the full abstract on PubMed
Practical Takeaways
- •Subchondral radiolucencies in juvenile Thoroughbred fetlocks may result from repetitive microtrauma rather than developmental osteochondrosis alone—consider management strategies that reduce concussive loading in young horses
- •Clinical detection of MFC lesions should focus on younger foals (<7 months), where lesions are more likely to have axial location and may be easier to identify on imaging
- •The presence of fibrin and fibroplasia in most lesions indicates an acute-to-chronic disease process; early intervention targeting inflammation and mechanical unloading may improve outcomes
Key Findings
- •19.1% of juvenile Thoroughbreds had CT-detectable MFC subchondral radiolucencies (SR), predominantly in foals <7 months of age with axial location shifting to central location in older animals
- •Chondronecrosis was present in 82.6% of SR+ lesions but absent in 4 cases and in all SR- control foals, suggesting osteochondrosis is not the sole cause
- •73.9% of SR lesions showed osteochondral separation with fibrin and fibroplasia, indicating both acute traumatic events and chronic remodeling
- •Thickened cartilage overlying all subchondral radiolucencies suggests trauma as an alternate or additional aetiological pathway compared to classic osteochondrosis