Accessory Ligament of the Deep Digital Flexor Tendon of the Horse Forelimb and Its Relationship with the Superficial Digital Flexor Tendon: A Plastination, Histological, and Morphometry Study.
Authors: Eren Gulsum, López-Albors Octavio, Guilabert Segura Ruth, Jordan Montesinos Joana, Latorre Rafael
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Understanding the anatomy of the deep digital flexor apparatus is fundamental to diagnosing and managing flexor tendon pathology in sport horses, and this 2024 investigation by Gulsum and colleagues adds important detail to our knowledge of how the accessory ligament (AL-DDFT) interacts with the superficial digital flexor tendon (SDFT) within the metacarpal region. Through macroscopic dissection, plastination, and histological analysis of forelimbs from horses aged 1–6 years, the researchers identified a previously undercharacterised fibrous band connecting the AL-DDFT to the SDFT, which transmits the common synovial sheath and carries associated epiligament and peritenon collagen fibres—a finding that may explain how load is distributed across these critical structures during movement. The study also identified two distinct morphological variants of the AL-DDFT (Type I and Type II), with Type II specimens displaying significantly greater cross-sectional area, suggesting considerable variation in individual anatomy that could influence biomechanics and injury susceptibility across the population. For practitioners, these findings underline the need for detailed ultrasonic and clinical assessment of the entire flexor apparatus as an integrated functional unit rather than as isolated structures, whilst the morphological heterogeneity observed raises important questions about whether anatomical variation predisposes certain horses to specific patterns of tendon and ligament injury. Future research correlating these anatomical variants with clinical outcomes in working horses would help clarify the practical significance of this structural diversity for injury prevention and rehabilitation protocols.
Read the full abstract on PubMed
Practical Takeaways
- •Understanding the fibrous connection between AL-DDFT and SDFT is important for interpreting imaging and recognizing how injuries to one structure may affect the other through their shared synovial sheath
- •Recognition of two distinct AL-DDFT types (Type I and II with different cross-sectional areas) may help explain variation in clinical presentations and injury patterns between individual horses
- •This detailed anatomical knowledge supports more accurate clinical assessment of metacarpal region pathology and can guide treatment planning for flexor tendon injuries
Key Findings
- •A fibrous band connection was identified between the AL-DDFT and SDFT, extending the common synovial sheath with associated collagen fibrils of epiligament and peritenon
- •Two distinct morphological types of AL-DDFT were identified, with Type II showing significantly greater cross-sectional area than Type I
- •Plastination-based morphological and histological evaluation revealed detailed anatomical relationships within the metacarpal region previously underexplored in equine literature