Morphometric study of the equine navicular bone: comparisons between fore and rear limbs

Area of Science:

• Equine anatomy
• Veterinary orthopedics
• Biomechanics

Background:

• The navicular bone (distal sesamoid bone) plays a crucial role in equine forelimb and hindlimb locomotion.
• Understanding its morphometry and histomorphology is essential for diagnosing and treating conditions like navicular syndrome.

Purpose of the Study:

• To establish anatomic bases for morphometry and histomorphometry of equine navicular bones.
• To investigate variations in navicular bone dimensions and structure between forelimbs and hindlimbs.
• To correlate bone architecture with mechanical loads experienced during locomotion.

Main Methods:

• Morphometric analysis of navicular bones from 95 sound horses, accounting for age, gender, weight, and size.
• Histomorphometric study of navicular bones from 61 sound horses.
• Detailed examination of cortical and cancellous bone, porosity, mineralized cartilage, and ligament attachments.

Main Results:

• Navicular bone dimensions (excluding thickness) were significantly larger in the forelimbs compared to hindlimbs.
• Forelimb navicular bones exhibited less cortical bone and more cancellous bone, with increased porosity and mineralized cartilage.
• Unique flexor surface cortical zones were identified in forelimb navicular bones, suggesting specialized adaptation.

Conclusions:

• Differences in navicular bone morphometry and histomorphology between forelimbs and hindlimbs reflect adaptations to distinct mechanical demands.
• The observed structural variations in forelimb navicular bones are likely related to higher forces encountered during exercise and rest.
• Findings provide a foundation for understanding biomechanical adaptations and potential pathologies of the equine navicular bone.