Development of the navicular bone in foetal and young horses, including the arterial supply.
Authors: Rijkenhuizen, Németh, Dik, Goedegebuure
Journal: Equine veterinary journal
Summary
# Development of the Navicular Bone in Foetal and Young Horses The navicular bone undergoes considerable vascular remodelling during foetal and early postnatal life, yet little was known about the normal timeline and patterns of these changes. Rijkenhuizen and colleagues examined the gross anatomy, arterial supply, and histological structure of navicular bones from 33 foetuses and 55 young horses to characterise normal developmental progression and identify when pathological changes first appear. By mid-gestation (125 days), dual blood supply routes were present—one superficial within the fibrocartilage and one resembling the mature pattern—but the superficial vessels regressed gradually after 270 days' gestation and disappeared entirely by six months postnatal. Macroscopic thinning of the fibrocartilage began at two months after birth, affecting approximately 45 per cent of bones by one year of age, whilst arterial wall changes (intimal thickening and elastic membrane splitting) appeared as early as four weeks postnatal and became increasingly prevalent thereafter. Notably, radiographic abnormalities (nutrient foramen enlargement) correlated strongly with fibrocartilage thinning and arterial pathology, with affected bones showing arterial wall changes in 25–80 per cent of vessels compared to only 6–20 per cent in radiographically normal bones. These findings establish the normal vascular ontogeny of the navicular bone and suggest that radiographic changes detectable from two weeks postnatal may reflect underlying arterial remodelling that predisposes to navicular disease later in life, emphasising the importance of early detection and management of developmental anomalies.
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Practical Takeaways
- •Early radiographic changes (nutrient foramina enlargement) visible within 2 weeks of birth may predict later navicular pathology; monitor young horses showing these signs closely
- •Significant arterial wall changes occur in the first weeks of life in susceptible horses; understanding this developmental timeline helps explain why navicular problems often emerge in young performance horses
- •Horses with radiographic abnormalities show 3-4 times higher rates of arterial pathology than normal horses, supporting radiographic screening as a useful prognostic indicator for navicular disease risk
Key Findings
- •Dual blood supply in navicular bone exists until 6 months after birth, then superficial vessels regress completely
- •Radiographic abnormalities (nutrient foramina enlargement) first appear at 14 days after birth, preceding arteriographic changes at 10 weeks
- •Arterial wall intimal thickening begins at 4 weeks after birth, with 25-80% of arteries affected in bones showing radiographic abnormalities versus 6-20% in normal bones
- •Fibrocartilage thinning detected macroscopically at 2 months after birth, present in 45% of navicular bones by 7-12 months of age