Osteochondrosis in the central and third tarsal bones of young horses.
Authors: Olstad Kristin, Ekman Stina, Björnsdóttir Sigriður, Fjordbakk Cathrine T, Hansson Kerstin, Sigurdsson Sigurdur F, Ley Charles J
Journal: Veterinary pathology
Summary
# Osteochondrosis in Central and Third Tarsal Bones: Evidence of Developmental Vascular Compromise Using micro-computed tomography and histological examination, researchers investigated osteochondrosis lesions detected in 16 of 23 equine fetuses and foals (aged 0–150 days), comprising predominantly Icelandic horses alongside standardbreds, warmbloods, and coldbloods. The central and third tarsal bones undergo a complex dual ossification process—both endochondral and intramembranous—with critical changes occurring between 105 and 150 days of age, during which cartilage canal vasculature progressively regresses and fibrous tissue replaces growth cartilage on dorsal and plantar surfaces. Histological analysis confirmed radiological osteochondrosis defects in three cases, revealing two distinct pathological mechanisms: necrotic vessels with surrounding ischemic chondrocyte death (articular osteochondrosis), and viable but retained hypertrophic chondrocytes indicating failed chondrocyte maturation (physeal osteochondrosis). The evidence strongly supports vascular insufficiency as the underlying cause of these lesions, with the critical window appearing to occur as cartilage canal blood supply fails around 4–5 months of age. For equine professionals, these findings underscore the developmental vulnerability of tarsal bones during late fetal and early foal life, suggesting that nutritional support, exercise management, and maternal health during pregnancy warrant careful attention, though further investigation into breed susceptibility and preventative strategies is needed.
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Practical Takeaways
- •Osteochondrosis in the central and third tarsal bones is common in young foals and is primarily driven by vascular failure during critical development windows (before 150 days of age).
- •Understanding the natural progression of ossification and cartilage canal regression in these bones helps distinguish between pathological lesions and normal developmental variations.
- •Early radiological detection of incomplete ossification or focal defects in young foals warrants investigation, as they may represent clinically significant osteochondrosis lesions that could impact soundness.
Key Findings
- •Osteochondrosis lesions were detected in 16 of 23 equine fetuses and foals (70%) using micro-computed tomography and histological examination.
- •Cartilage canal vessels were present in most cases up to 122 days of age but were absent by 150 days, indicating regression of blood supply to growth cartilage.
- •Radiological osteochondrosis defects resulted from vascular failure characterized by necrotic vessels, ischemic chondronecrosis, and retention of hypertrophic chondrocytes.
- •Central and third tarsal bones developed through both endochondral and intramembranous ossification, with dorsal and plantar aspects transitioning from growth cartilage to fibrous tissue between 4 and 105 days of age.