Laminitis is an avascular necrosis involving the sensitive
laminae, which intermesh with the horse's hoof wall. The hoof
(particularly the capillary blood supply) appears to be a target
organ for endotoxins, which can be released as a result of a
variety of causes. While the blood supply to the feet is the
main area apparently affected, it seems likely that other vascular
beds are also involved. However, the unique housing of the
blood supply to the foot in a nonexpandable structure (the hoof)
may accentuate the impact of blood flow changes. Systemic
hypertension is found in the early stages of the diease. The
end mediators of the endotoxins are prostaglandins that affect
flood supply to the feet, leading to opening of arteriovenous
anastomoses. The outcome is a loss of blood supply to the
laminae, despite an increase in blood flow to the foot.
Leading to degeneration and then failure of the attachments
between the coffin bone and the inner hoof wall.
Seen on the xray as rotation of coffin bone down. The most
common causes are grain engorgement, qrazing in lush pastures,
postfoaling metritis, and systemic gram-negative bacterial
infections. In fat ponies, it is common to find laminitis
during the spring months, when the soluble carbohydrate content
increases in grasses and clovers.