Microvasculature of the suspensory ligament of the equine hind limb

Abstract

Abstract OBJECTIVE To describe the microvascular anatomy of the equine hind limb suspensory ligament. ANIMALS 18 hind limbs harvested from 9 adult horses euthanized for reasons unrelated to lameness. METHODS A catheter was placed in the transected cranial tibial artery at the level of the mid-distal tibia for each hind limb and used to inject 120 to 150 mL of contrast medium (2 limbs) to identify principal vasculature using contrast-enhanced CT or India ink (11 limbs) to identify microvasculature using the Spalteholz tissue-clearing technique. Routine histologic evaluation was performed on transverse sections from 4 hind limbs. RESULTS The hind limb suspensory ligament is principally supplied by branches of the medial and lateral plantar metatarsal arteries and, to a lesser extent, the medial and lateral plantar arteries as well as the associated proximal and distal deep plantar arches. A uniformly distributed intraligamentous microvascular supply was observed without relative deficiencies in vascularity between the proximal, midbody, and distal regions. Histologic examination supported these findings, demonstrating a network of connective tissue surrounding and entering the suspensory ligament containing cross-sections of branches of the principal vasculature. CLINICAL RELEVANCE The equine hind limb suspensory ligament has a uniformly distributed and abundant microvascular supply throughout its length, with no evidence of relative deficiency of vascular supply in any region. A region of hypovascularity does not appear to be a viable explanation for the high rate of injury to and commonality of lameness associated with the proximal hind suspensory ligament in horses.