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EQUINE VETERINARY EDUCATION / AE / SEPTEMBER 2017


reassess vascular flow at the anastomosis site was not possible in this case due to the noncompliance of the owner (mare now turned away in foal).


Discussion


Traumatic injuries to the horse are common, particularly concerning the distal limb (Owen et al. 2012). Lacerations involving neurovascular structures can result in significant loss of circulating volume and/or loss of function of the regions


a)


Fig 2: Doppler ultrasound image of the medial digital vein (left) and artery (right) distal to the repair at the level of the first phalanx 5 days post operatively confirming flow and patency of the vessel.


b)


supplied by these structures (Stashak and Theoret 2013). In the distal limb, traumatic lacerations of neurovascular structures are often managed by local pressure bandaging, debridement and ligation. Vascular thrombosis and severe nerve damage following traumatic or iatrogenic injury can lead to subsequent tissue loss through ischaemic necrosis (Turner 1985). Vessel occlusion and ligation can be associated with haemodynamic disturbances, ranging from transient oedema to tissue ischaemia and necrosis (Nazzal et al. 1994). In the equine distal limb, arterial occlusion may result in catastrophic loss of the hoof and associated structures. Restoration of vascular supply would therefore negate this complication. Arterial supply to the equine foot has symmetrical medial


and lateral branches of the digital arteries distal to the fetlock joint. At this distal location the fore- and hindlimb supply are identical (Dyce et al. 2002). The first set of dorsal branches arise at the level of the first phalanx with the palmar (or plantar) branches continuing distally. Branches to the digital cushion arise at the level of the proximal interphalangeal joint and pass axially to the hoof cartilages. A second set of dorsal branches arises at the level of the second phalanx which also helps supply the dermis of the hoof (Dyce et al. 2002). The terminal palmar (or plantar) branches anastomose to form a terminal arch within the third phalanx and it is this arch which provides collateral circulation within the hoof. It is unknown if the collateral circulation could sustain a complete arterial occlusion at a more proximal location, such as the level of the proximal sesamoid bones, as occurred in this case report. Repair of blood vessels should result in a return of


Fig 1: Intraoperative images. Proximal is to the left of the image. a) A 14 gauge catheter was inserted into the distal portion of the medial digital artery to maintain patency. b) Medial digital artery following 2 layer anastomosis.


© 2016 EVJ Ltd


function, as demonstrated in this case by Doppler ultrasound and removes the reliance on collateral circulation to compensate for loss of blood supply. Primary anastomosis of vascular structures, such as the medial digital artery, should therefore be considered a viable option in equine cases where laceration of a main vessel occurs. Trauma involving vascular structures in the extremities is also a common injury in human emergency medicine where repair rather than ligation or compression is commonly the treatment of choice in the absence of a more urgent injury demanding


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