Histological study of navicular bone disease

Area of Science:

• Equine Podiatry
• Veterinary Pathology
• Histology

Background:

• Navicular disease is a common cause of forelimb lameness in horses.
• The exact etiology of navicular disease remains debated, with theories including ischemia and mechanical stress.

Purpose of the Study:

• To histologically investigate the aetiology of radiological findings in equine navicular bones.
• To assess bone vitality and remodeling activity in horses with navicular disease.

Main Methods:

• Histological examination of navicular bones from 8 horses with navicular disease.
• Tetracycline labeling in two horses to evaluate bone vitality and remodeling rates.
• Microscopic assessment for osteoclasts, osteoblasts, osteoid formation, and tetracycline uptake.

Main Results:

• No evidence of bone necrosis or loss of vitality in diseased areas.
• High rates of bone resorption and formation (remodeling) were observed in all cases.
• Microscopic findings indicated significant osteoblast and osteoclast activity and high tetracycline uptake.

Conclusions:

• Navicular disease is likely a consequence of increased bone remodeling, not primary ischemia.
• Altered pressure from the deep flexor tendon and increased load on the foot's caudal part contribute to the condition.
• The disease is potentially reversible through interventions like corrective shoeing to alter load distribution.