Pathological changes in the navicular bone and associated structures of the horse.

The research investigates the pathological changes in the navicular bones of 74 horses aged between 8 months and 30 years, including 8 with a history of navicular disease. The study reveals that such changes are often related to age, with the likelihood of degenerative lesions and osteophytes increasing with age, but independent of lameness. In horses with navicular disease, these alterations were more extensive and accompanied by further complications.

Sample and Methodology

• The study involved 74 horses of varying ages, from 8 months to 30 years.
• Out of these, 8 horses had a previous clinical history of navicular disease, a condition affecting the horse’s bone and surrounding structures.
• The researchers conducted a necropsy, or autopsy, on the navicular bones from these animals to investigate the pathological changes.

Main Findings

• Degenerative lesions in two key areas – the fibrocartilaginous surface of the navicular bone and deep flexor tendons – were found to be age-related changes, implying that they do not have direct relations to lameness or mobility issues of the horses.
• In horses suffering from navicular disease, these lesions were more extensive and often paired with adhesions and subchondral cavitation of the fibrocartilaginous surface of the navicular bone. This suggests that navicular disease exacerbates these conditions.
• Osteophytes (bone spurs, which are indicators of joint degeneration) were found in 12 out of the 74 horses, showing that such developments are common with aging, but are not common in horses with navicular disease.

Additional Observations

• The nutrient foramina, openings on the distal border of the navicular bone, showed considerable variability in size and shape across the studied horses. Particularly, in horses with a history of navicular disease, the external opening was often smaller than the internal part.
• Arteriosclerosis, or hardening of the arteries, was identified in both healthy horses and those with a history of navicular disease. The disease, therefore, does not seem to have specific links with navicular disease.
• Contrary to potential expectations, neither thrombosis (blood clots within arteries) nor ischemic necrosis of bone (bone cell death due to insufficient blood supply) was found in any of the examined cases.