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

This research article presents the findings from a histological and arteriographic study conducted on 35 navicular bones from 19 healthy adult horses. The study describes the structure and pathways of the arterial blood supply to the navicular bone, and reveals some diseases related changes to the vessels.

Understanding the Arterial Blood Supply of the Navicular Bone

• The researchers analyzed the arterial blood supply to the navicular bones in horses, employing both arteriographic and histological methods. This provided a detailed mapping of the arteries supplying the navicular bone, and offered precise insights into the cellular composition.
• They found that the blood arrives at the navicular bone from four main directions: distal (from the bottom), proximal (from the top), medial (from the middle), and lateral (from the side). This complex network ensures that all areas of the bone receive adequate nutrients and are well oxygenated.
• The bone itself could be subdivided into areas, based on the direction from which they receive arterial supply. Some areas received arterial inflow from only one direction, others from two, and still others from three. The largest part of the navicular bone, however, received supply from the distal portions or bottom.

The Nutrient Foramen and Connectivity

• The distal arteries, those supplying the largest region of the navicular bone, enter through openings known as nutrient foramen. These hollow channels carry not only blood vessels, but also loose connective tissue and myelinated nerves, thus serving as essential conduits for both nutrient supply and neural signaling.
• Of interest, the study found that at least 77% of these nutrient foramina also contain synovial membrane, a crucial component typically found in joint spaces. This suggests the presence of a unique microenvironment that might carry distinct physiological and cellular properties.

Histological Changes in the Navicular Bone Arteries

• In the last part of their study, the researchers examined the cellular structure of the arteries in the bone, noting any histological changes that might hint at disease or aging. They found such changes in 12% of the navicular arteries.
• The changes included thickening of the intima, the innermost lining of the blood vessels, often accompanied by a splitting of the internal elastic membrane (the layer just outside the intima). Additionally, signs of pathologic tissue remodeling such as the buildup of glassy, translucent hyaline material (hyalinization), formation of excess fibrous connective tissue (fibrosis), and enlargement of the muscle layer (hypertrophy) in the blood vessels wall (media) were observed.