Canon Bone
Lower limb swelling
There are many causes of generalized swelling of the lower limbs in horses. Some horses will get swellings due to rest and will not show a lameness, however, may be slightly stiff. In these cases there is no pain on palpation and the limb feels cool. The swelling will often resolve after exercise and can be reduced by stable bandages. If there is no improvement on exercise or the swellings are not associated with rest, the condition should be further investigated as may be due to heart problems, anaemia or a vasculitis (inflammation of the blood vessels) and should be treated accordingly. If one limb is affected and the animal is lame with a hot painful swelling, with or without a wound, the cause is usually traumatic. The swelling should be fully investigated and the underlying cause treated. In some cases the soft tissues are infected (cellulitis). The horse will usually show a severe lameness but will fully weight bear. This lameness will often improve on walking, however, attempting to walk a severely lame horse should not be attempted without veterinary supervision. Cellulitis is usually treated with antibiotics, bandaging and anti-inflammatory drugs.
Bucked shins
This condition is seen in young racehorses due to fatigue damage to the canon bone. Affected horses have pain when the front of the canon is palpated but lameness is often not present.
Diagnosis
Diagnosis is made by radiography and bone scanning (nuclear scintigraphy).
Treatment
The horse should be rested and anti-inflammatory drugs such as phenylbutazone (‘bute’) used. Regular cold water hosing is often carried out to help reduce the swelling. Prevention, which is better than treatment, is achieved by gradually increasing work load.
Canon bone fracture
Fractures of the canon bone will usually cause a sudden, severe lameness, usually non-weight bearing, and have severe pain and swelling on palpation. A suspected fracture is an emergency and a veterinary surgeon should be called before attempts are made to move the animal. A large bandage with a splint should be applied to support the limb.
Diagnosis
Radiographs and to assess treatment options, although, in many instances examination of the animal can provide enough information as to whether the fracture is treatable or not.
Treatment
Fractures of a long bone in the horse generally carry a poor prognosis. Certain fractures can be treated surgically, however, euthanasia on humane grounds must be considered for all canon fractures.
Splints
A splint is a boney growth on one of the splint bones. They are usually caused by stresses being placed on the splint bones during exercise and usually occur on the splint bone on the inside of the limb.
Signs
A hard swelling can be felt along the splint bone. The lump may be hot and painful to palpate in the early stages (acute). It is in these early stages that a lameness may be seen. Later on the lump remains yet no pain or lameness is associated with it (chronic).
Diagnosis
Radiographs are required for diagnosis.
Treatment
In the acute phase the horse should be rested and anti-inflammatory drugs, such as phenylbutazone, (‘bute’) used. Regular cold water hosing is often carried out to help reduce the swelling.
Splint bone fracture
Fractures of the splint bone are usually caused by trauma, e.g. a kick, however, can occur spontaneously due to excessive forces being applied to them during fast gaits. Horses will have heat, pain and swelling over the splint bone and will show a marked lameness initially. In cases of a kick wound there is commonly a wound associated with the splint bone.
Diagnosis
Radiographs are required for diagnosis.
Treatment
Most fractures will heal spontaneously with box rest, wound care and bandaging. In some cases, especially when a portion of bone has become infected and causes a persistent infection (sequestrum), part of or all of the splint bone can be removed surgically.