Puncture wounds are common in horses, and are the most common cause of subsolar sepsis. The majority of puncture wounds result only in sepsis of the subsolar soft tissue (ie, subsolar abscess), but can be catastrophic when the puncture is in the frog and travels deep enough to enter synovial structures such as the navicular bursa, the distal interphalangeal joint, or the deep digital flexor tendon sheath.
Puncture of the sole by a foreign body is associated with introduction of pathogenic microorganisms that lead to subsolar abscess formation. Lameness is usually severe; the degree of lameness may be similar to that of a fracture. The horse may stand pointing the affected foot. There is commonly a prominent digital pulse in the affected limb. If allowed to progress, the abscess may travel proximally to rupture at the coronary band; there will usually be edematous swelling proximal to the coronary band prior to rupture. Diagnosis is made by confirming the site of pain by pulling the shoe, using hoof testers, and picking or paring the suspect area to locate the foreign body or its dark tract. If a foreign body is found in the frog, it may be best to obtain a lateral radiograph of the foot to assess the structures penetrated prior to removing the offending object. If a tract is found in the frog, it should be probed and a radiograph taken with the probe in place. Because puncture wounds in or near the frog commonly enter a synovial structure, they constitute a serious problem requiring rapid, aggressive diagnosis and therapy. If a synovial structure is entered, the horse should be placed on broad-spectrum antibiotics and transported to a facility capable of advanced surgical and medical techniques; the affected synovial structure should be lavaged with sterile polyionic solution as soon as possible (within hours).
If a puncture wound is noted in the solar area, ensuring adequate drainage from the site helps prevent abscess formation. If there is a suspected abscess but no tract is found, the foot can be poulticed in an attempt to promote organization of the abscess for localization. If a tract is found that leads to a subsolar abscess, adequate drainage should be established with a hoof knife; the drainage hole should be kept as small as possible (~0.5–1 cm diameter) to avoid a prolapse of sensitive corium. Some farriers and veterinarians prefer to drain the abscess through the hoof wall (instead of the sole) if possible. The abscess should then be probed to determine its extent; a palmar digital nerve block will usually be necessary prior to probing and lavage of the area. If the abscess underruns a large area of the foot, it can be lavaged by placing a 14-gauge catheter or teat cannula into the affected subsolar space and flushing with saturated Epsom salt solution (made by adding Epsom salts to boiling water or saline until some salt crystals sit on the bottom of the container and will not go into solution). If a chronic subsolar abscess has developed, this treatment may have to be repeated. The foot should then be kept in a rubber or plastic boot for several days; a cotton pad soaked in saturated magnesium sulfate solution or other suitable poultice can be applied to the foot for 12 hr/day until all drainage ceases. All horses with puncture wounds should be immunized against tetanus. Local and systemic antibiotic therapy are not necessary for a sole abscess, but must be used aggressively if sepsis of a synovial structure occurs.
Last full review/revision March 2012 by Stephen B. Adams, DVM, MS, DACVS; Joerg A. Auer, DrMedVet, Dr h c, MS, DACVS, DECVS; James K. Belknap, DVM, PhD, DACVS; Jane C. Boswell, MA, VetMB, CertVA, CertES (Orth), DECVS, MRCVS; Peter Clegg, MA, Vet MB, PhD, CertEO, DECVS, MRCVS; Andrew L. Crawford, BVetMed, CertES (Orth), MRCVS; Jean-Marie Denoix, DVM, PhD, Agregé; Marcus J. Head, BVetMed, MRCVS; C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DACVS, DACVSMR; James Schumacher, DVM, MS, DACVS, MRCVS; John Schumacher, DVM, MS, DACVIM; Roger K. W. Smith, MA, VetMB, PhD, DEO, DECVS, MRCVS; Chris Whitton, BVSc, FACVSc, PhD