Microvasculature of the suspensory ligament of the equine hind limb

Megan R. Williams DVM, DACVS Evan Crisman VMD, and Brianne M. Taylor DVM, MS, DACVP

Background:

This study focuses on the microvascular anatomy of the equine hind limb suspensory ligament, an area previously underexplored compared to the forelimb. Given the high rate of injury and the severe impact on horse performance, understanding the microvascular supply could advance treatment and prevention strategies.

Methods:

The study involved 18 hind limbs from 9 horses euthanized for reasons unrelated to the study. Techniques used included contrast-enhanced CT, India ink injection for microvasculature identification via the Spalteholz tissue-clearing technique, and routine histologic evaluation of transverse sections. The objective was to observe the vascular distribution within the suspensory ligament.

Results:

The findings indicate a uniformly distributed microvascular supply across the proximal, midbody, and distal regions of the suspensory ligament. Both imaging and histological analyses showed that a deficiency in the vascular supply is unlikely to be the cause of the high injury rate in the proximal region of the hind limb suspensory ligament. This contrasts with previous beliefs and hypotheses suggesting regional hypovascularity as a potential cause of frequent injuries.

Limitations:

The study is limited to anatomical and histological observations in euthanized animals and does not account for blood flow dynamics in live animals, which could affect the results. Additionally, the study does not quantitatively measure blood flow, which could provide more detailed insights into vascular supply and potential regional deficiencies.

Conclusions:

The study provides comprehensive insights into the microvascular structure of the equine hind limb suspensory ligament, demonstrating a robust vascular supply that does not vary significantly between different regions of the ligament. These findings suggest that other factors, possibly mechanical or related to tissue composition, may contribute to the high incidence of injuries rather than a lack of vascular supply. This lays a foundation for future research into the physiological responses of these ligaments to stress and injury.

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