Blog Post - Kissing Spines
Kissing spines (also known as spinous process impingement or overriding dorsal spinous processes) is a condition that is gaining increasing attention among horse owners and within the equine industry. So, what exactly is kissing spines, what causes it, and what can we do about it?
What is kissing spines?
Kissing spines describes the condition which occurs within the thoracolumbar spine of horses characterised by evidence of impingement or contact between one or more dorsal spinous processes of neighbouring vertebrae.
As mentioned previously, kissing spines can occur anywhere along the length of the horse’s back, and commonly occurs within the thoracic portion of the spine (the portion of the spine that is joined by the ribcage, underneath where the saddle sits) or the lumbar portion of the spine (from the end point of the horse’s ribcage until the junction with the pelvis.)
How do we diagnose kissing spines?
The presence of kissing spines is most commonly diagnosed via X-rays. Best practice dictates the use of high-powered mounted X-ray, due to both the ability to use higher exposures, and optimise radiation safety for person/s taking the X-ray images. An aluminium wedge is commonly used to “even out” the tissue density between the spinous processes and the vertebrae to avoid “anatomic clipping” which can result in certain areas being clipped out of the image due to differences in radiation absorption from different tissue densities.
Evidence of kissing spines can also be seen on ultrasound evaluation of the back, which is often a useful adjunctive tool to assess if there is other pathology in the region of the back which may be contributing, or causing, back pain.
How common is kissing spines?
Kissing spines has been found to occur in 39% of the horse population (Turner 2011), however is not always associated with back pain. Care should be taken to not over-interpret the presence of kissing spines when evaluating a horse with back pain.
A recent study (Patterson Rosa et al., 2024) identified a genetic component to kissing spines, with two genetic markers on one chromosome (chromosome 25) having a significant relationship with the severity of the condition. The study included both Warmblood and stock-type breeds (such as Paints and Quarter Horses) which identified the genetic factor within all studied breeds.
Above: An X-ray highlighting the presence of kissing spines. Image Source: Dr Jackie Hill from https://thehorse.com/148184/kissing-spines-horses-back-pain/
How do we treat kissing spines?
Treatment of kissing spines is highly dependent on practitioner preference. A recent international survey of equine surgical specialists (Treß, Lischer, Merle, & Ehrle, 2024) revealed a significant variation in treatment recommendations according to the region from which the specialist originated, with specialists in Europe being more likely to recommend manual therapy than specialists from the USA. Surgical intervention was recommended as a first-line therapy was recommended mainly by specialists working in the UK, USA or Ireland, however 71% of respondents said they preferred conservative management and recommended surgery only in horses that did not respond to conservative therapy.
The most common forms of “conservative” veterinary intervention includes ultrasound-guided local injection (usually with a corticosteroid such as triamcinolone acetate) as well as controlled exercise.
Exercise should ideally be targeted to reduce the degree of postural lordosis of the spine (dipping of the back) to reduce contact between the spinous processes of adjacent vertebrae, strengthening the topline and increasing the muscle mass and activation of the multifidus muscle, which is integral to stabilisation of the spine (and is commonly reduced in size in both horses and humans with back pain!)
Equipment can be utilised to increase the degree of postural stabiliser musculature engagement (including the multifiduc) such as the Equiband. Other aids can include lungeing with a Lunge Aid, Pessoa or Equiami system, which are particularly useful in horses with thoracic kissing spines due to the action of the nuchal ligament increasing the tension on the supraspinous ligament when the head is lowered, therefore increasing the space between spinous processes.
Other important exercises include dynamic mobilisation exercises and abdominal lifts (mentioned in a previous blog post), polework, as well as thoroughly warming up the tissues of the back before asking for engagement/an increase in work demand.
Above: Systems such as the Equiband Pro may be useful in increasing the activation of spinal stabilisation musculature including the Multifidus muscle. Photo source: https://ridingmagazine.com/2023/08/03/equicore-concepts-equiband-pro-system/
References
Turner, T. A. (2011). Overriding spinous processes ("Kissing Spines") in horses: Diagnosis, treatment, and outcome in 212 cases. In Proceedings of the American Association of Equine Practitioners Annual Convention, San Antonio, 2011. American Association of Equine Practitioners.
Patterson Rosa, L., Whitaker, B., Allen, K., Peters, D., Buchanan, B., McClure, S., Honnas, C., Buchanan, C., Martin, K., Lundquist, E., Vierra, M., Foster, G., Brooks, S. A., & Lafayette, C. (2022). Genomic loci associated with performance limiting equine overriding spinous processes (kissing spines). Etalon, Inc., Menlo Park, CA, USA.
Treß, D., Lischer, C., Merle, R., & Ehrle, A. (2024). International survey of equine orthopaedic specialists reveals diverse treatment strategies for horses with overriding spinous processes. Veterinary Record.
Ellis, K. L., & King, M. R. (2020). Relationship between postural stability and paraspinal muscle adaptation in lame horses undergoing rehabilitation. Journal of Equine Veterinary Science, 91, 103108. https://doi.org/10.1016/j.jevs.2020.103108