The radiographic development of the distal and proximal double contours of the equine navicular bone on dorsoproximal-palmarodistal oblique (upright pedal) radiographs, from age 1 to 11 months.
Authors: Dik K J, van den Belt A J, Enzerink E, van Weeren P R
Journal: Equine veterinary journal
Summary
# Editorial Summary: Radiographic Development of the Equine Navicular Bone in Young Foals The proximal articular contour of the navicular bone—whether concave, undulating, straight or convex—is known to be heritable and represents a significant predisposing factor for navicular disease, yet uncertainty has surrounded when horses achieve their mature radiographic bone architecture. Dik and colleagues conducted serial upright pedal radiographs on 19 Dutch Warmblood foals from 1 month to 11 months of age at four-weekly intervals, tracking the ossification and contour development of both the distal and proximal double contours visible on dorsoproximal-palmarodistal oblique views. The distal double contour (representing the articular border and flexor cortex border) became apparent by 1–2 months with clear definition by 3–4 months, whilst the proximal double contour developed more slowly, with the characteristic mature shape typically recognisable by 7 months and consistently obvious by 9–11 months. This early establishment of the bone's mature conformation—appearing well before skeletal maturity—argues against shape determination being primarily force-dependent (contrary to Wolff's law), instead suggesting that the navicular's morphology is predetermined, with its biomechanical consequences potentially driving disease susceptibility. Practically, this enables radiographic assessment and shape classification from 12 months onwards to identify individual and breed predisposition to navicular disease, allowing informed breeding decisions and early implementation of preventative management strategies in susceptible animals.
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Practical Takeaways
- •Radiographic evaluation of navicular bone shape for predisposition to navicular disease can be reliably performed from 12 months of age in young horses
- •Hereditary proximal articular border shape appears fixed early in development and may identify individual and breed susceptibility to navicular disease before clinical signs appear
- •The early manifestation of mature radiographic appearance supports early identification strategies for at-risk foals, potentially enabling preventive management decisions
Key Findings
- •The distal double contour of the navicular bone becomes visible within the first 1-2 months of life, with clear manifestation by 3-4 months
- •The proximal double contour develops later, becoming clearly visible from 9 months of age
- •The mature shape of the proximal articular border (concave, undulating, straight, or convex) becomes recognizable from 7 months and is always obvious by 9-11 months
- •The navicular bone achieves its mature radiographic appearance during the first year of life, suggesting shape is genetically determined rather than force-dependent