Epiduroscopy: an exciting window into back pain in horses
Dr Timo Prange
Read full study online here: 2016 Jan;48(1):125-9. doi: 10.1111/evj.12470
Published in European Trainer - October - December 2017, issue 59
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Back pain is a well known cause of lameness, gait alterations and poor performance in sport horses. Up to 25% of dressage horse owners report back problems in their animals, but not only sport horses are affected.
Although racehorses compete at a younger age than other equine athletes, they might suffer from back pain more often than we think, autopsy studies have identified pathological changes in the back of the majority of examined young thoroughbreds. Until recently, it has been very difficult to investigate back pain and it is easy to overlook this as a cause of disappointing performance. A novel surgical technique which has recently been reported in Equine Veterinary Journal, may change all this.
How can epiduroscopy help veterinarians to find the source of pain in a horse with back problems?
While the spinal cord sends and receives signals directly from the brain, the spinal nerves are the communication pathway between the spinal cord and the body. Spinal nerves are, among other things, responsible for the movements of the muscles in the back and legs and for sending information about pain in the back and legs back to the brain. Injury to a spinal nerve can result in dysfunction of muscles or in pain. Fortunately, the spinal nerve roots are well protected from injury, first by the surrounding bony vertebrae and, after leaving the spinal canal, by a thick muscle layer. However, the nerve can be injured at the point where it exits the spinal canal. The spinal nerves exit the canal through the openings between two adjacent vertebrae. The opening is called the intervertebral foramina. Each opening is in close proximity to the facet joints that connect the vertebrae. Inflammation of these joints (facet joint arthritis) causes back pain and results in irregular growth of bone around the arthritic joint.
While severe bony changes can be picked up on radiographs, subtle changes can easily be missed. Unfortunately, even relatively small bony growths can impinge on the passing nerve and cause irritation and inflammation. Nerve root impingement is a recognized cause of lower back and leg pain in people and now that we have epiduroscopy available for horses, it will be possible to identify the prevalence and importance of this condition in equine athletes. This will be especially interesting for young racehorses, where facet joint arthritis can be found in the thoracolumbar spine of up to 97% of cases that undergo autopsy but currently there is no information about the effects of this arthritis on passing spinal nerves.