34th Annual Scientific Meeting proceedings

Wounds involving the hoof capsule need specific management tailored to the particularities related to wound characteristics, biomechanics, and healing.

Due to their closeness to the ground, wounds involving the hoof capsule are often very contaminated. In horses kept in the field or loose housing, a hoof wound may be overlooked for days, resulting in infection being established at the time of presentation. Another characteristic of wounds involving the hoof capsule is the frequent occurrence of foreign body embedment. This can be dirt, manure particles or straw, as well as glass, metal or wood splinters being embedded after the horse kicking through windows, plates or walls.

Due to the rigid nature of the hoof capsule, particularly the hoof wall, fracturing with compete avulsion is much more common than tearing (albeit not in the coronary band and heel bulbs, where lacerations may occur). The anatomy and rigidity of the hoof capsule imparts specific healing characteristics: wound edges will not retract or gape after injury, swelling cannot occur under the hoof capsule, adequate drainage is difficult to obtain, and healing of the hoof wall relies on horn regrowth rather than on the contraction and epithelialization known from dermal wounds. There is extensive movement of wound edges, as the elastic heel cushion of the hoof results in expansion of the hoof capsule and stretching of the tissues with every step the horse takes.

Taken together, the above-mentioned particularities of wounds involving the hoof capsule have the consequences that healing is protracted and costly, and complications such as subsolar abscesses, septic arthritis of the distal interphalangeal joint, septic chondritis, formation of exuberant granulations tissue, horn spurs or hoof wall defects, fracturing or septic osteitis of the distal phalanx, and support limb laminitis are relatively common. To reduce risk of complications, wound management needs to be specifically directed at abating the issues arising from the anatomy and healing characteristics of the hoof capsule.

With wounds involving the hoof capsule, it is very important to be cognizant of foreign bodies and injury to vital structures. Imaging, e.g., native and contrast radiographs, ultrasonography, native and contrast CT, and MRI, is therefore of paramount importance. It is the author’s preference to manage horses with wounds involving the hoof capsule under general anesthesia to facilitate detection and management of injury to vital structures underlying the hoof capsule (pedal or navicular bones, navicular bursa, digital flexor tendon sheath, distal interphalangeal joint, deep digital flexor tendon, collateral cartilages, vascular and neural structures etc.).

Management of wounds involving the hoof capsule should follow general wound management principles, i.e. thorough debridement and lavage followed by suturing. Delayed primary or secondary closure is relevant for many hoof wounds to ascertain that the wound is clean at the time of suturing. This entails an initial 3 or more days long period of open wound management with topical antiseptics or antimicrobials to reduce bioburden in the wound. Debridement of devitalized tissues and removal of bone fragments is required for healing to proceed.

Reconstructing the coronary band is of great importance in order to avoid hoof wall defects and horn spurs. Avulsed horn segments can either be removed distal to the coronary band or retained and stabilized. With the latter approach the surgeon may choose to suture the avulsed segment onto the hoof wall after thinning it with a motorized burr or immobilizing the segment using metal implants inserted in the outer insensitive portion of the hoof wall.

Postoperative immobilization in a slipper, foot or half-limb cast and stall rest for several weeks is followed by 2-4 months’ convalescence. Close collaboration with a skilled farrier is highly advantageous, as the horse may need long-term therapeutic farriery such as hospital plates, egg bar and/or heart bar, frog support pads with packing etc.

Suggested reading

1. Céleste, C.J., Szöke, M.O. 2005. Management of equine hoof injuries. Vet. Clin. Equine, 21:167-190
2. Fürst, A.E., Lischer, C.J. Foot. In: Equine Surgery, 5^th ed., eds. Jörg Auer, John Stick, Jan Kümmerle & Timo Prange, Elsevier, Missouri, USA. Pages 1543-1587
3. Honnas, C.M., Dabareiner, R.M., McCauley, B.H. 2003. Hoof wall surgery in the horse: approaches to and underlying disorders. Vet. Clin. Equine, 19: 479-499
4. Parks, A.H. 1997. Wounds of the equine foot: principles of healing and treatment. Eq. Vet. Edu., 9: 317-327
5. Pollitt, C.C., Daradka, M. 2004. Hoof wall wound repair. Eq. Vet. J., 36: 210-215
6. Schumacher, J., Stashak, T.S. 2017. Management of wounds of the distal extremities. In: Equine Wound Management, 3^rd ed., eds. Christine Theoret & Jim