What does it mean when people say a horse has “kissing spines”? The term kissing spines refers to the impingement or overriding of the dorsal spinous processes of the thoracolumbar vertebrae. In order to understand this, let’s review some anatomy. The horse has 7 cervical vertebrae, 18 thoracic vertebrae (Arabians have 17), 6 lumbar vertebrae, and 18 coccygeal vertebrae. The thoracic and lumbar vertebrae have dorsal processes that extend upwards like the fin of shark. In a normal back, these dorsal processes should have plenty of space between them. In horses affected by kissing spine, the processes are interfering with one another. This interference can cause inflammation and pain.
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What causes kissing spines?
The development of kissing spines is likely multifactorial. A genetic and hereditary component cannot be excluded, and a poorly fitted saddle and poor training can contribute. For instance, horses that are ridden with a hollow back and those who do not have proper development of their top-line musculature are predisposed. Some experts think that athletic activity, even in good form, causes or contributes to kissing spines. Kissing spines can be diagnosed on radiographs and nuclear scintigraphy. However, just because a horse has kissing spine lesions on diagnostic imaging does not mean that they are experiencing clinical signs or that they require treatment. Studies have not been able to show any correlation between diagnostic imaging lesions and clinical signs.
The development of kissing spines is likely multifactorial. A genetic and hereditary component cannot be excluded, and a poorly fitted saddle and poor training can contribute. For instance, horses that are ridden with a hollow back and those who do not have proper development of their top-line musculature are predisposed. Some experts think that athletic activity, even in good form, causes or contributes to kissing spines. Kissing spines can be diagnosed on radiographs and nuclear scintigraphy. However, just because a horse has kissing spine lesions on diagnostic imaging does not mean that they are experiencing clinical signs or that they require treatment. Studies have not been able to show any correlation between diagnostic imaging lesions and clinical signs.
Clinical signs thought to be related to kissing spines include sensitivity on back palpation, “girthiness,” sensitivity to brushing, poor performance and/or bad behaviour under saddle. However, there are many other differentials for these clinical signs including gastric ulcers, muscle disorders, and ovarian pain in mares. Injury and arthritis can occur between the facets of the thoracic vertebrae as well as within the vertebral disc spaces. These facets and disc spaces require ultrasound in order to be imaged. Back pain may also be secondary to lameness issues in the hind end. To determine if a horse’s diagnostic imaging lesions are the source of their clinical signs, local anesthetic (i.e. lidocaine/mepivacaine) can be injected into the affected area(s). If the horse’s clinical signs do not improve with local anesthetic, then their kissing spine lesions are likely not the cause of their clinical signs. However, some horses will not improve because they have chronic back pain that cannot be blocked out entirely.
In the top image, pe-operatively, the dorsal spinous processes are close together. The bone between the interspinous spaces is sclerotic (red arrows) which indicates that it is reacting to the interference between the processes. The second image is post-operatively, where the bone has been removed and the spaces are now wider.
What are the treatment options?
Treatment options for kissing spines can involve physiotherapy, chiropractic work, mesotherapy, shockwave, and local infiltration of corticosteroids between the affected dorsal spinous processes. Some horses can be managed very well with medical treatment alone. The best candidates for surgical correction are those horses that respond well to medical treatment but require treatment to be repeated in short time intervals.
What does surgery involve?
Depending on the degree of impingement between the dorsal spinous processes, the impinging bone is either removed (cranial ostectomy) or the ligament between the processes is cut (interspinous ligament desmotomy). If no complications arise, horses can generally be reintroduced to work 2 months after the procedure. In one study of 30 horses who received surgical correction for kissing spines, 93% returned to the same level of intended work.
If you feel that your horse is exhibiting signs of back pain, ensure that their saddle is properly fitted and consult a veterinarian. We spend a lot of time on our horses’ backs, and they deserve to be pain-free.
Article Written by Dr. Shelby Krywonos
About Dr. Shelby Krywonos
Dr. Shelby Krywonos, DVM born and raised in Vernon, BC. Animals have been an integral part of her life for as long as she can remember and are what fostered her passion for veterinary medicine. Growing up, she competed locally in the hunters and jumpers as well as obtained her practical HB2 and written A levels in the Canadian Pony Club. She completed three years of undergraduate studies in biology before moving to Saskatoon, SK, to obtain her Doctor of Veterinary Medicine degree. She graduated with distinction in the top 15% percent of her class. Dr. Krywonos completed a 1-year rotating equine internship at Paton and Martin Veterinary Services. She worked in this referral hospital, managing critical cases, assisting in surgery, and running anesthesia. She also gained valuable experience in ambulatory work.
She is currently part of the team at Larch Veterinary Services, a veterinary medical mobile facility serving Enderby, BC, and surrounding areas. larchvetservices.com
References:
Pressanto, M. C., Pepe, M., Coomer, R. P., Pilati, N., & Beccati, F. (2023). Radiographic abnormalities of the thoracolumbar spinous processes do not differ between yearling and trained thoroughbred horses without perceived back pain. Journal of the American Veterinary Medical Association, 1–8. https://doi.org/10.2460/javma.22.09.0419
Beaumont, A., Bertoni, L., & Denoix, J. M. (2021). Ultrasonographic diagnosis of equine thoracolumbar articular process joint lesions. Equine Veterinary Education, 34(11), 592–599. https://doi.org/10.1111/eve.13551
De Souza, T. C., Crowe, O. M., Bowles, D., Poore, L. A., & Suthers, J. M. (2021). Minimally invasive cranial ostectomy for the treatment of impinging dorsal spinous processes in 102 standing horses. Veterinary Surgery, 51(S1). https://doi.org/10.1111/vsu.13736
