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Equine Back Pain Due to Kissing Spine

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The mare that pins her ears as you tack her up. The colt who bites and strikes when asked to back up. The gelding who just seems a little “off” every time he rounds into frame. If you’ve ever dealt with these issues before, you’ve witnessed firsthand the symptoms of back pain. Lameness and behavioral problems due to back pain are more common than many realize. Luckily, veterinarians have a variety of options in their toolkit to keep your horse pain-free under saddle.

Back pain is a common source of subtle or hard to diagnose lameness. Horses often react by bucking, kicking, biting, or otherwise resenting saddling or motions that cause flexion of the spine, such as backing. They may also have trouble collecting, changing leads, and performing other advanced maneuvers under saddle. There are many causes for back pain in horses. In simple cases it may be related to muscle soreness, but often it stems from the vertebrae themselves.

Vertebral Structure

Each vertebra of the spine is composed of different parts:

  • a “body,” which is below the spinal cord,
  • a “spinal canal,” which the spinal cord passes through,
  • “transverse processes,” which extend to either side of the spinal canal,
  • ‘vertebral facets’ which are the articulations between each vertebra as well as the ‘intervertebral disc space’ and ‘disc’ between the body of the vertebrae,
  • and a “spinous process,” which extends dorsally above the spinal canal.

"Overriding spinous processes, or “kissing spine,” occurs when the vertebrae are too close together. When the spinous processes touch, movement makes these bones grate against each other, causing intense pain.

Diagnosing Back Pain

Veterinarians use palpation and advanced imaging techniques, such as scintigraphy (“bone scan”) and thermography, to help locate the source of pain. Spinal radiographs are also taken to determine which vertebrae are affected. Once identified, they will often block the back with local analgesia to confirm the diagnosis.

Medical Treatment

There are a variety of ways to treat kissing spine. Medical management is often the first step. This includes 3-12 months of rest, extracorporeal shockwave therapy, and corticosteroid injections. Acupuncture, chiropractic treatment, and massage may also contribute to pain reduction. After the rest period is completed, a physical therapy regimen is started. Riding in a low frame, ground poles, and other exercises that strengthen the core and epaxial muscles can help stabilize the overriding vertebrae. Medical management may work for a short while, but often needs to be repeated as the disease progresses, depending on the severity of the change in the dorsal spinous process and the interspinous ligaments between.

Surgical Procedures

If these therapies no longer work, surgery is the next step. There are two main types of back surgery used to relieve the pain from kissing spine. Interspinous ligament desmotomy is a relatively quick procedure and can be performed standing or under general anesthesia. The interspinous ligament is a ligament that runs between each dorsal spinous process and helps hold them together. During an interspinous ligament desmotomy, radiographs are used to determine which vertebrae are affected. The horse is then heavily sedated and an incision is made above the affected portion of the spine. The interspinous ligament is surgically cut to release the tension and allow the vertebrae to move further apart. Nerves are also cut to desensitize the ligament. This is repeated along the spine until all of the impinged vertebrae are corrected.

The second type of surgery used is a dorsal spinous process subtotal ostectomy. This procedure is more invasive but can be more useful for severe disease. During this surgery, the horse is induced under general anesthesia and placed on its side. An incision is made over the affected vertebrae and a portion of the dorsal spinous processes of every other vertebra is removed using an oscillating saw or osteome. Although part of the vertebra is removed, these horses do not suffer from instability or have problems with saddle fit. They can go back to riding within 3-6 months.



Recovery

After surgery is performed, the path to recovery requires 3-6 months of rehabilitation. Horses normally stay on stall rest and slowly incorporate hand-walking, lunging and back strengthening exercises. Flexibility rehabilitation, including carrot stretches and ground poles, can begin immediately after surgery. After completion of the rehabilitation period, about 82-95% of interspinous ligament desmotomy cases return to riding, with 53% achieving an equal or greater level of performance. After subtotal ostectomy, about 72% of cases return to full function.

Back pain can put a huge roadblock in your horse’s career, but your veterinarian can help. Through medical rehabilitation or surgical intervention, they can put your horse back on track to achieve your riding goals.



References:

  1. Coomer RPC, McKane SA, Smith N, et al. A controlled study evaluating a novel surgical treatment for kissing spines in standing sedated horses. Vet Surg 2012;41:890-897.
  2. Walmsley JP, Pettersson H, Winberg F, et al. Impingement of the dorsal spinous processes in two hundred and fifteen horses: case selection, surgical technique and results. Equine Vet J 2002;34:23-28.
  3. Prisk, Amanda J., and José M. García‐López. "Long‐term prognosis for return to athletic function after interspinous ligament desmotomy for treatment of impinging and overriding dorsal spinous processes in horses: 71 cases (2012–2017)." Veterinary Surgery7 (2019): 1278-1286.
  4. Brink, Palle. "Subtotal ostectomy of impinging dorsal spinous processes in 23 standing horses." Veterinary Surgery1 (2014): 95-98.

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