Anatomical, magnetic resonance imaging and histological findings in the accessory ligament of the deep digital flexor tendon of forelimbs in nonlame horses.
Authors: Nagy A, Dyson S
Journal: Equine veterinary journal
Summary
# Editorial Summary: Normal Anatomy and MRI Appearance of the Accessory Ligament of the Deep Digital Flexor Tendon Nagy and Dyson's detailed anatomical and imaging analysis established the first comprehensive reference for normal AL-DDFT morphology in sound horses, addressing a significant gap in the literature that has hampered diagnostic interpretation. Through dissection, high- and low-field MRI, and histological examination of cadaver limbs, the researchers documented considerable natural variation in both structure and appearance: cross-sectional areas ranged from 68.1 to 299 mm², oblique bands of higher signal intensity appeared in 69% of limbs on high-field imaging, and histological sections revealed thicker collagen bundles with greater cellularity than the deep digital flexor tendon itself, often arranged in characteristic oblique configurations. Notably, these structural variations bore no significant relationship to age, sex, breed, height or weight—meaning they represent inherent individual differences rather than age-related changes or bodyweight effects. When evaluating lame horses with carpal or metacarpal pain on MRI, clinicians must account for this substantial baseline variation in nonlame individuals; what may appear as pathological change could reflect normal anatomical presentation, necessitating correlation with clinical findings and careful comparative assessment rather than relying on MRI appearance alone for diagnostic certainty.
Read the full abstract on PubMed
Practical Takeaways
- •MRI appearance of the AL-DDFT is highly variable in normal horses; oblique signal intensity bands and size variation should not be automatically interpreted as pathological when evaluating lame horses
- •Understanding normal AL-DDFT anatomy and its fibrous connections to adjacent structures (SDFT and DDFT) is essential for accurate MRI interpretation in lameness investigations
- •The greater cellularity of AL-DDFT compared to DDFT may affect signal characteristics on MRI and should be considered when assessing ligament integrity in clinical cases
Key Findings
- •AL-DDFT cross-sectional area in proximal 7 cm metacarpal region ranged from 68.1–299 mm², showing large variability in nonlame horses
- •Oblique bands of higher signal intensity were identified in 69% of high-field MRI images, representing normal anatomical crimp patterns in collagen bundles
- •AL-DDFT cellularity was significantly greater than in the deep digital flexor tendon in all examined limbs
- •No significant relationship between age, gender, weight, or height and AL-DDFT cross-sectional area or presence of oblique signal intensity bands