Magnetic resonance imaging and histological findings in the proximal aspect of the suspensory ligament of forelimbs in nonlame horses.
Authors: Nagy A, Dyson S
Journal: Equine veterinary journal
Summary
# Editorial Summary Nagy and Dyson's 2012 investigation used high- and low-field MRI alongside histological analysis of cadaver forelimbs from 30 nonlame horses to establish baseline anatomical and imaging standards for the proximal suspensory ligament (PSL)—a critical structure often implicated in forelimb lameness but previously undocumented in detail. The researchers identified important correlations between horse size and PSL cross-sectional area, with both height and bodyweight showing significant positive associations (P<0.001), whilst also discovering substantial individual variation in the composition, shape and signal intensity of muscular and adipose tissue within the PSL across the population. High signal intensity on MRI corresponded to adipose tissue and intermediate intensity to muscle, enabling practitioners to distinguish tissue types; the medial lobe was consistently smaller than the lateral lobe. The authors' key finding—that considerable normal variation exists in PSL appearance between nonlame horses—has direct clinical relevance: clinicians must exercise caution when interpreting PSL lesions on MRI and avoid over-pathologising subtle signal changes without correlating imaging findings with lameness localisation, palpation findings and clinical progression.
Read the full abstract on PubMed
Practical Takeaways
- •When evaluating MRI images of lame horses with suspected PSL injury, remember that normal horses show considerable variation in PSL appearance—variation alone does not indicate pathology
- •Larger horses will naturally have larger PSL cross-sectional areas; this should be accounted for when comparing MRI findings between individual horses
- •Understanding normal MRI signal patterns (collagen as low-intermediate, muscle as intermediate, fat as high signal) is essential for accurately identifying abnormal lesions on imaging
Key Findings
- •PSL collagenous tissue shows low to intermediate signal intensity on MRI depending on pulse sequence used
- •Large variability exists among horses in amount, shape and signal intensity of muscle and adipose tissue within the PSL
- •Medial lobe of PSL has smaller cross-sectional area than lateral lobe, with positive association between CSA and both horse height and bodyweight (P<0.001)
- •High signal intensity on MRI corresponds to adipose tissue while intermediate signal intensity corresponds to muscle tissue within the PSL