Role of navicular bone shape in the pathogenesis of navicular disease: a radiological study

From progeny lists of 30 Dutch Warmblood sires, 586 3-year-old females by these stallions were randomly selected, each progeny group aimed at 20 animals for statistical reasons. The front feet of the sires and female progeny were examined radiographically using lateromedial and dorsopalmar upright pedal projections. The radiological features associated with navicular disease were classified 0-4 using a standardised classification, grades 3 and 4 representing the more severe changes. The shape of the proximal articular border of the navicular bone outline on the dorsopalmar view was classified 1-4; 1=concave; 2=undulating; 3=straight; 4=convex. A significant shape-grade association was found, the highest grades 3 and 4 incidence demonstrated by shape 4. In shapes 1 and 2, navicular bones grades 3 and 4 features were mainly characterised by inverted flask-shaped channels. In shape 3, navicular bones grades 3 and 4 were dominated by enthesiophytes. These findings indicate an apparent shape predisposition to radiological changes associated with navicular disease. The shape of the navicular bone in the offspring was on average the same as the sire, indicating an hereditary element in navicular bone shape.