The effects of heavy falls on horses *H&H Plus*

A hefty fall can leave a horse winded, but how do we know if he has suffered internal injury, asks Gil Riley MRCVS

After a heavy fall, it is important to establish what, if any, injuries the horse has sustained.

If he can’t stand, he may be winded – a spasm of the diaphragm as a result of sudden force applied to the abdomen – or have a broken limb or an injury to the spine or head. A horse who is merely winded should be back on his feet within 10 to 15 minutes. If he stays down, the likelihood is that much more serious damage has occurred.

A thorough examination should identify any architectural changes to the horse’s external anatomy. Failure to bear weight on a leg could indicate a broken bone or torn muscles in the proximal (upper) limb; moving the limb may result in crepitus, a grating sound or unpleasant sensation produced by friction between bone and cartilage in a joint or the fractured parts of a bone. Injury to the pelvic musculature or the pelvis itself can render a horse very reluctant to walk or weight-bear on one or more limbs.

The challenge is to ascertain whether any damage is superficial or deep, so any vets in attendance must be allowed time and space to examine the animal thoroughly. If serious injury is present, it can take considerable time to gather sufficient clinical evidence to be able to reach an accurate diagnosis.

Bumps and bruises

Falling on heavy ground can cause bruises – ruptures of the small blood vessels (capillaries) underneath the skin. If the ground is hard, damage may be greater, with abrasion to the skin.

A deeper bruise presents as a fluid-filled lump (haematoma), where underlying tissues have bled or oozed serum to create a “balloon” under the skin. The damaged blood vessels bleed until there is sufficient pressure from fluid accumulation within the haematoma to halt the bleeding and allow clotting. If there is major disruption of deeper tissues, there may be torn muscles as well as bruising. Always try to keep the horse calm, since excitement will increase blood pressure and lead to more bleeding.

While a haematoma is developing, it may be possible to control the bleeding and minimise swelling by applying direct pressure and ice to the site – as long as it is in an accessible area where the horse will tolerate it. Cold should be applied for no more than 20 minutes at a time, and only for as long as the area feels warm and soft. Later, after the haematoma has stabilised, warm packs can increase circulation and stimulate healing.

Haematomas are often sterile swellings, so there is little pain or inflammation. Most resolve, if given enough time, so are best left alone. No attempt should be made to drain a haematoma until the damaged vessels have sealed, as opening it up may allow bleeding to resume. If it continues to grow, however, then surgery to ligate (tie) the vessel responsible may sometimes be necessary.

Once a haematoma is “mature”, usually around two weeks after forming, careful drainage with a sterile needle can be considered to minimise long-term scarring or to speed up healing.

If it has developed a subcutaneous pocket, where the skin is no longer attached to the underlying tissue, it may refill with serum. There is also the risk that bacteria is introduced, converting a sterile pool of serum into a painful abscess.

A blood test helps identify the severity of any internal or external haemorrhage by measuring the haematocrit, the level of red blood cells in circulation. Results must be carefully interpreted, however, as horses have large reserves of blood in the spleen and may not appear obviously anaemic, especially in the early stages as everything stabilises.

High levels of muscle enzymes measured in a blood test, proteins found mainly in muscle tissue, will indicate muscle damage. Very high levels are associated with bruising and trauma to the muscles of the hindquarters or back, where most of the muscle tissue is found.

Difficult diagnosis

Ruptures of internal organs such as the spleen or intestine, or the diaphragm (the muscular curtain that separates the chest cavity, or thorax, from the abdomen), are rare.

More commonly, fracture of one or more ribs can cause penetration of the space around the lungs, called the pleural cavity. The resulting pneumothorax (collapsed lung), usually evident because the horse is struggling for breath, can sometimes be resolved with rapid surgical intervention.

While many limb fractures are untreatable and result in euthanasia, some may be corrected. Most can be identified using radiography (X-ray), but nuclear scintigraphy may be required to diagnose hairline distortions in the bone (stress fractures), or fractures within large amounts of muscular tissue impenetrable to X-rays or even ultrasound (in the femur or hip, for example, in the larger horse).

Examination of the pelvis is difficult due to its musculature; the only palpable areas are the points of the hip (tuber coxae) and the tuber sacrale at the highest extremity of the back. Impact with the ground can result in a piece of the tuber coxa breaking off. Since the tuber coxae serve as the origin of some of the gluteals, the largest muscles of the hindquarters, recovery may be prolonged and lameness long term.

After a fall, swimming can be a useful addition to box rest and walking out, as it allows the horse to recuperate without weight bearing and to achieve mobility of damaged muscles and joints. Physiotherapy can help return elasticity to tissues and mobilise scar tissue, minimising the formation of constrictions and adhesions and breaking down those already present.

Up and over

Rearing and toppling over backwards can cause skull fractures. In the case of the basisphenoid bone, at the base of the skull, this can lead to a catastrophic cerebral haemorrhage and rapid death. Blood emerging from the ear after a bad fall is invariably a serious sign, indicating a fracture of important bones in the skull.

Sitting down

If the hindlegs are underneath, the tuber ischii – the point of the pelvis nearest to the tail and an anchor for muscles in this region – can suffer bruising or fracture. Profound hindlimb lameness on that side can develop and the muscles of the tail head will start to atrophy, or waste, within days.

Lameness resulting from trauma to the region can resolve, but requires recuperation of four to six months.

Falling onto belly

Falling with one or both hindlimbs stretched out behind classically leads to rupture of the peroneus tertius – a tendinous structure that runs from the lower end of the femur and over the front of the hock, inserting in the upper front of the cannon bone. This muscle ensures that as the stifle flexes, the hock flexes also, so an affected horse may appear normal at walk but will trot with a profound lameness.

Full recovery is possible after a minimum of three months’ box rest and the introduction of a walking-out programme.

The splits

This typically happens on slippery or icy ground (below) and causes extreme forces to be applied to the muscles on the inside of the thigh and limb. Common injuries sustained are to the adductor muscles of the femur and the collateral ligaments of the hock.

Recovery is dependent on rest and physiotherapy. Where ligament damage involves the hock, an arthroscopy (keyhole) procedure to debride damaged ligament tissue can be beneficial before recovery can begin.

Ref: Horse & Hound; 3 December 2020

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