Kinematics of the equine distal sesamoid (navicular) bone of the thoracic limb.
Authors: Elane, Biedrzycki, McCarrel, Banks, Morton
Journal: American journal of veterinary research
Summary
# Editorial Summary Understanding how the navicular bone moves throughout the stride is fundamental to diagnosing and managing problems within the podotrochlear apparatus, yet precise data on its kinematics has been lacking until now. Elane and colleagues used computed tomography imaging combined with medical modelling software to track the three-dimensional movement of the distal sesamoid bone across 30 equine thoracic limbs positioned in extension (200° metacarpophalangeal angle), neutral (180°), and maximal flexion (110°). The navicular bone demonstrated substantial distal translation during flexion—up to 5.4 mm in intact limbs and 6.2 mm in partial limbs—alongside significant dorsal translation during extension (approximately 1.4 mm), with notable rotation around the mediolateral axis during both extension (17.1°) and flexion (2.6°). Critically, movement of the navicular bone was significantly reduced in limbs with transected flexor tendons compared to intact specimens, demonstrating that soft-tissue structures profoundly influence distal limb mechanics beyond their immediate anatomical role. For practitioners, these findings reinforce the importance of evaluating the entire functional unit—bone, cartilage, and soft tissues together—rather than viewing navicular pathology in isolation, whilst highlighting that future research linking these biomechanical parameters to clinical lameness presentation will be essential for refining diagnosis and therapeutic strategies.
Read the full abstract on PubMed
Practical Takeaways
- •Understanding DSB kinematics provides baseline data for evaluating how pathologic changes in the navicular apparatus may contribute to clinical lameness
- •Flexor tendon integrity significantly influences navicular bone movement; injuries or surgical procedures affecting these tendons will alter normal biomechanics
- •This kinematic data may inform farriery and therapeutic approaches to navicular syndrome by clarifying normal motion patterns and how pathology disrupts them
Key Findings
- •Dorsal translation of the DSB was significant during extension (1.4 mm full limbs, 1.3 mm partial limbs, P < 0.001)
- •Distal translation was significant during extension (1.9 mm full, 1.1 mm partial) and maximal flexion (5.4 mm full, 6.22 mm partial, P < 0.001)
- •Angular rotation about the mediolateral axis was significant during extension (17.1° ± 1.4°) and flexion (2.6° ± 1.3°, P < 0.001)
- •Partial limbs (with transected flexor tendons) demonstrated significantly reduced DSB movement compared to full limbs (P < 0.001), indicating flexor tendon transection alters distal thoracic limb kinematics