Relationships of age and shape of the navicular bone to the development of navicular disease: a radiological study.

This study investigates the impact of age and the shape of the navicular bone on the development of navicular disease in horses. It specifically focuses on the potential effects of age on the previously noted predisposition of certain bone shapes to the disease.

Study Design and Objectives

• The study aimed to evaluate any age-related implications of the reported shape predisposition to navicular disease.
• This was done by estimating the shape of the proximal articular border of the navicular bone and grading the radiological navicular bone condition, with grades 3 and 4 representing the most severe changes.
• The research involved a total of 920 Dutch Warmbloods, comprising 746 normal and 174 clinically affected horses aged 3 to 19.

Findings on Shape-Grade Association and Age

• The research discovered a significant shape-grade association that was independent of age in both normal and affected horses. This reinforces the notion that the shape of the navicular bone plays a fundamental role in predisposing horses to navicular disease.
• An age-related increase in the prevalence of the least susceptible bone shape was found in older, normal horses.

Disease Progression and Grade Dependence

• In the context of disease progression, researchers noted a low prevalence (average 15%) of severe grades 3 and 4 changes in normal horses, but a high prevalence (average 85%) of these changes in the affected horses.
• This suggests that the clinical presentation of navicular disease is dependent on the grade of changes, rather than the shape of the navicular bone.

Age-Related Findings in Clinically Affected Horses

• In horses affected by navicular disease, there was a significant age-related appearance of inverted flask-shaped channels and enthesophytes (bone spurs at the attachment of a tendon or ligament).
• However, considering the significant association between the shape of the bone and radiological features previously reported in 3-year-old normal horses, the relationship to these features may depend more on the shape of the bone than the age of the horse.

Summary

• The results of the study suggest that the shape of the navicular bone has a fundamental impact on the predisposition to navicular disease.
• The grade of changes in navicular bone condition is more influential in disease manifestation over the shape of the bone.
• New age-related features observed in clinically affected horses might still be more dependent on the shape of the bone than on the age of the horse.