The arterial supply of the navicular bone in the normal horse.

An arteriographic and histological study of the arterial blood supply of 35 navicular bones, from 19 adult horses with no clinical or radiographical signs of navicular disease, is described. The arteries enter the navicular bone from four directions: distal, proximal, medial, and lateral. The navicular bone can be divided into areas which receive arteries from one, two, or three directions, whereas the distal supply covers the largest part of the navicular bone. The distal arteries enter the navicular bone through the nutrient foramen which contains loose connective tissue, nutrient vessels and myelinated nerves. At least 77 per cent of the nutrient foramina contains synovial membrane. Twelve per cent of the arteries in the navicular bone show histological changes. Thickening of the intima with or without splitting of the internal elastic membrane and hyalinization, fibrosis and hypertrophy of the media were observed.