The deep digital flexor tendon in the equine toe
Authors: König H E, Macher R, Polsterer-Heindl E, Hinterhofer C
Journal: Pferdeheilkunde Equine Medicine
Summary
# Editorial Summary König and colleagues investigated how toe conformation influences biomechanical loading in the equine digit by examining 30 Warmblood horses with radiographs and ultrasound imaging, measuring dorsal metacarpophalangeal joint (DMPJ) angle alongside phalangeal dimensions and flexor tendon cross-sectional areas. The research revealed that proximal and middle phalangeal length and angulation showed moderate but significant negative correlations with DMPJ angle (r = −0.28 to −0.45), meaning steeper pasterns were associated with more closed fetlock angles, whilst notably, neither hoof angle nor flexor tendon size demonstrated meaningful correlation with DMPJ positioning. Bilateral asymmetries emerged for DMPJ angle and pastern angulation—important findings that challenge assumptions of symmetry in limb conformation assessment—and taller horses demonstrated slightly more closed DMPJ angles. For practitioners, these results suggest that pastern morphology (particularly length and angle of the proximal and middle phalanx) represents the primary conformational determinant of metacarpophalangeal joint loading, making detailed pastern evaluation more predictive of tendon strain than distal hoof variables or static tendon measurements alone. Whilst the static radiographic approach has limitations in capturing dynamic loading patterns during movement, these findings offer practical guidance for shoeing strategies and orthopaedic management tailored to individual pastern conformation rather than relying on hoof angle as a proxy for digit biomechanics.
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Practical Takeaways
- •Assess pastern angulation and length as key indicators of load on the DMPJ and flexor tendons when evaluating individual conformation for lameness risk
- •Hoof angle alone is not a reliable predictor of tendon load or injury predisposition; evaluate the entire toe-fetlock complex instead
- •Check for left-right asymmetries in fetlock angles and phalangeal conformation, which may influence shoeing recommendations and injury risk
Key Findings
- •Proximal and middle phalanx length and angle showed significant negative correlation with DMPJ (r = -0.28 to -0.45, p<0.04)
- •Hoof angle and distal phalanx angle showed no noticeable correlation with DMPJ or flexor tendon cross-sectional area
- •Significant left-right asymmetries existed for DMPJ and phalangeal angles (p<0.002)
- •Wither height showed moderate negative correlation with DMPJ (r = -0.31, p=0.04)