Your Horse’s Health

LAMENESS

OLIVER C. DAVIS

CONDITIONS OF THE FOOT

BRUISING (Subsolar Bruising)

Bruising of the foot occurs most frequently in horses suffering from thin soles and/or collapsed heels. Laminitic horses also suffer from subsolar bruising as the normally concave sole becomes flatter. Exercise on hard ground exacerbates the problem, but it is wrong to think that bruising is restricted solely to hard ground. Bruising often occurs under really soft, wet conditions in which the foot sinks in the mud onto exposed rock and gravel. Bruising that occurs at the heel is often referred to as ‘corns’. Clinically, the symptoms range from mid low-grade lameness to an acute onset of severe lameness. There may be a pulse in the foot. In mild cases, this pulse may be exacerbated by making the horse walk several steps, so check its intensity immediately after leading it. Hoof testers may also indicate the area of lameness, as may careful cleaning and paring of the foot to look for signs of discoloration.

Treatment As a general rule, bruises need not be opened. Systemic use of NSAIDs (bute) can help in reducing the discomfort. Poultices are not recommended as they will only soften the foot further and make a secondary bacterial infection more likely. Hygiene is very important to prevent infection, and the hoof should be bandaged after first scrubbing it thoroughly with a surgical cleanser. It is advisable to remove the shoe if it is pressing on the sole, and to reduce the wear upon the applied bandage.When shoeing a flat foot prone to bruising, careful attention should be placed on seating out the inside of the shoe so that the weight of the leg rests on the wall of the hoof alone, and not on the sole. Horses with corns may also benefit from the use of bar shoes in order to distribute the weight more evenly, or in severe cases, to suspend that particular heel off the shoe entirely. Regular trimming and shoeing will be necessary if conformational problems exist.

Above: Hoof testers are essential for locating pain within the hoof.

HOOF ABSCESS (Subsolar Abscess)

The inner structures of the hoof are a perfect breeding ground for anaerobic bacteria to multiply. These can gain access either via cracks within the hoof surface, or foreign body penetration, or even ‘pricked’ feet when the hoof nail becomes too close to the sensitive structures of the foot. Horses that are already suffering with founder (chronic laminitis) or seedy toe are particularly at risk. The lameness is acute and very painful, so much so that novices often diagnose a broken leg. The leg is non weight-bearing, and I have even experienced recumbent horses groaning in agony. If there is no obvious sign of a fracture, begin your examination with the foot. Remember, the intensity of the pulse in the palmar digital arteries of the foot will be increased. An exception to this occurs on the occasion when a double sole has formed, which traps the infection. Therefore, a careful inspection with hoof testers is essential, as is careful palpation along the coronary band and the heel in order to ascertain if the infection is ready to burst from these softer, less rigid areas.

Treatment Hoof testers should localise the area with the most pain. In many cases the shoe must be removed to expose the area underneath. Careful paring of the foot with a knife will demonstrate if a puncture wound is present. If not, the area should be searched with a hoof knife until the infection is released. Adequate drainage is essential. The horse should only be poulticed for a few days, but it may be necessary to bandage for longer, depending on the extent of the injury. It is often helpful to have the foot re-examined and trimmed after poulticing when the horse is more comfortable, and to monitor the drainage allowed. Antibiotics will not affect infections within the hoof capsule as there is no blood supply there. Their use should be limited to occasions when the vital part of the foot is affected. NSAIDs may be helpful, though in my experience they are not particularly effective. Similarly, nerve blocks rarely block out the pain entirely and can often prove completely ineffective, therefore demonstrating the importance of the full clinical examination. Radiographs can also prove useful when trying to find deep abscesses that are difficult to get to. If a horse becomes suddenly lame again after initially releasing the infection, a problem with drainage may be present. However it should be remembered that over-poulticing of feet, particularly thin soled, flat feet, can also cause lameness, and these hooves only need drying out for the horse to become sound! Another problem can occur if the drainage hole is cut too deeply, allowing the sensitive corium underneath to protrude through. This is readily seen as a pink to deep red mushroom-like protrusion at the base of the drainage hole. It is sensitive to touch. This must be pushed back with the use of pressure! Fill the hole with gauze swabs, pushing the corium back behind the horn, and apply a pressure bandage. Caustic pencils or copper sulphate may also be useful. All horses with hoof infections should be up to date with their tetanus vaccination.

Above: An abscess has been found. Note the purulent grey pus oozing out.
Below: The infection has been cut out and the hoof carefully cleaned prior to bandaging.

CORONITIS

This is an inflammation of the coronary band, and is only seen rarely in laminitic horses and those suffering from systemic, often febrile illnesses. Clinical findings include swelling around the coronary band of the foot and the acute onset of lameness, with the horse reluctant to bear weight on one or more legs. Initially therefore, the disease is easy to mistake with abscessation or laminitis. Over a period of days, exudates development under the coronary band may increase until it finally bursts forth, causing a separation between the hoof wall and the coronary band.

Treatment It is difficult, and usually limited to pain relief. The prognosis is poor. In many cases which do resolve, abnormal hoof growth can occur. When considering whether or not euthanasia is appropriate, it is important to consider the aetiology of the disease. Certain cases warrant prevailing with. I once treated a pony that had caught its hind pastern in straight wire. Unusually this did not do too much damage initially, but in the coming week, the hoof slowly began separating from the coronary band: the wire had obviously cut off the blood supply to the foot. The entire hoof was removed, the exposed foot cleaned and carefully bandaged, and the pony placed on clean soft shavings. Surprisingly, it experienced only mild to moderate pain throughout its ordeal, convincing us to persevere. The satisfaction was immense when trimming the hoof eight months later revealed a completely normal hoof, and the pony was able to return to work.

CANKER

This refers to a condition in which the frog and related horn-producing structures of the horse’s foot begin to hypertrophy, and exude a foul smelling excretion.

Treatment Is usually prolonged and difficult, and consist of radical resection of the affected horn and treatment with stringents designed to dry and disinfect the bandaged hoof. Systemic treatment with antibiotics may also be prescribed concurrently. The prognosis in these cases is guarded.

HOOF WALL CRACKS (Sandcracks)

Hoof cracks can arise from a variety of causes. Although it may be a result of dehydration, horses with damage to the laminae (laminitis, seedy toe, long toe confirmation) are predisposed to this problem. Cracks will also arise if the coronary band has been damaged, in which case the crack will arise from the coronary band and extend distally; in the more usual scenario, the crack begins distally.

Treatment Many cracks are superficial, and apart from the application of hoof dressing to help with hydration, do not warrant any further treatment. Cracks that extend deeper into the sensitive structures of the foot, or continue to extend proximally towards the coronary band, do not need to be treated. The use of modern acrylics has greatly improved the treatment of cracks. However, corrective trimming and shoeing are still essential to success. If the crack occurs in the toe area, it is important to trim the toe back as far as possible. The entire crack should be resected out of the hoof wall, taking care to remove all dead tissue and dirt until the healthy tissue is found. In order to alleviate further pressure on the damaged area, I prefer to suspend this portion of the hoof wall. The hoof should be shod with a closed bar shoe in order to alleviate excessive movement in the area. Primary defects of the horn arising from a damaged coronary band can only be treated symptomatically.

KERATOMA

Although the name implies a cancerous tissue, keratomas are in fact masses of keratin-containing tissue growing between the hoof wall and pedal bone. As pressure is exerted upon the sensitive laminae and/or the pedal bone, they can cause the horse to go lame. They are also a continuous source of infection. Over time, keratomas can cause a pressure necrosis to the underlying bone. A history of intermittent lameness is common, before distortion of the coronet band and hoof wall comes visible. An examination using hoof testers produces a painful response. On the solar surface, a distortion of the white line may be present. A ring block of P3 or an abaxial nerve block is necessary in order to improve the lameness. Radiographically a discrete, well-circumscribed lytic area may be visible; however, this is not always the case. The lesion can usually be differentiated from septic bone due to the smooth borders and lack of sclerosis.

Treatment involves the complete removal of the keratoma. Although this can be performed in the standing horse, for larger lesions and more fractious horses, general anesthesia may be necessary. A tourniquet should be applied in order to minimize bleeding. Using an oscillating saw or motorized bur, two vertical cuts are made on either side of the lesion. The distal end of the hoof wall is then grasped and peeled upwards, taking care not to damage the coronet band. The mass is removed, and the underlying tissue is exposed. A bar shoe with large clips on either side of the defect is nailed on to stabilize the weakened hoof. The defect is then carefully packed in soaked povidone iodine swabs, and bandaged. These swabs and bandages should be changed every three days until the area is cornified. After this, the area may be filled. The stabilizing bar shoe should be retained until the defect has grown out completely.

Your Horse’s Health Lameness

by Oliver Davis MRCVS

Published by David & Charles

RRP: $49.99

A comprehensive guide aimed at giving you a better understanding of the causes, diagnosis and treatment of equine lameness

Oliver Davis MRCVS is the fourth generation of his family to become a vet and is the practice principal of a busy equine veterinary surgery. He trained in Munich before establishing The Whistlejacket Equine Veterinary Surgery near Blandford in Dorset, UK. Oliver writes regularly for Your Horse magazine.