PERHAPS no part of the horse is subject to such force during exercise than the back. With an average of 54 vertebrae from the neck to the tail (the number can vary from 51 to 58) it is a remarkable structure capable of withstanding considerable force.
The position and movement of the back is affected by the health, position and movement of the head and neck, the forelimbs, the pelvis, and the hindlimbs. With good back posture being critical to good performance, understanding more about how the horse's back works should be high on the list for every rider and trainer.
There are several parts of the back which contribute to some of the common diseases afflicting our horses and understanding the anatomy can help the rider steer physios and vets to the painful area. Because each vertebra is topped by a bony appendage of 5 – 25 cm in length, the so-called spinous process, the spine runs lower than you might think.
These spinous processes rise to form the withers and provide attachments for the ligaments and muscles. You may have felt these spinous processes as small bumps on the midline of the horses back. To each side of the spinous process is the Multifidous muscle, although all the muscles of this region are important, it is spasm of the multifidous muscle that is a primary cause of back pain in horses (and humans).
Diagnosing back pain can be a challenge because clinical signs are variable, subtle, and non-specific. They include, stiffness, refusing to work, head tossing and tail swishing, loss of hind limb propulsion (owners often liken this to having the brakes on), lameness, an abnormal reaction or sourness when saddling, mounting, or riding or bucking, stopping and bolting.
Investigation starts with a full examination and palpation. Your vet or physio should see the animal moving, including under saddle, and may use radiography (X-Ray), ultrasound or Scintigraphy (bone scan) to image the back.
Most horses are initially affected by spasm of the multifidous and other muscles, this is the horsey equivalent of human lower back pain and can be extremely debilitating. Medication with anti-inflammatories (usually this means injecting the back with corticosteroids and treating the horse with a drug such as phenylbutazone), physiotherapy and a controlled exercise program are the first line of treatment. Just as in humans, rest is contraindicated, and horses should be encouraged to work.
In some cases, muscle spasm can bring the spinous processes closer together such that they rub against one another. This impingement or kissing spines is a very common disease and affects all types of horses. It has been known since horses were first domesticated.
Most commonly diagnosed between the ages of 5 and 10, treatment is based on reducing the spasm and pain, initially with medication, but often surgery is required. Previously surgery for kissing spines was a major undertaking with a long recuperation period and variable results. Recently a new surgery was described which involves cutting the ligament between the spinous processes to allow normal back movement to return.
This so called minimally invasive surgery (because it is performed through small incisions with minimal trauma) is undertaken with the horse standing and sedated and carries a success rate of around 90-95%. Horses are able to return to work within 2-3 weeks. Many thousands of horses, of all types and uses, have now been treated in this way allowing pain free movement and a long and active athletic career.
If you think your horse may have back pain, contact your physiotherapist, or vet who will be glad to help.
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