Clinically relevant kissing spines can cause a range of pain or behavioral changes. Photo by Captivation Media
Back problems are a growing source of pain and performance issues in horses. One of the most recognized and frequently treated back conditions is overriding dorsal spinous processes, commonly known as kissing spines. This occurs when bony protrusions that extend up from the vertebral bodies touch instead of staying properly spaced. In some cases this contact leads to bony changes, remodeling and even cystlike lesions. Unfortunately, there is a lot we don’t know about why kissing spines develops and how significant the condition becomes when it does.
Identifying Kissing Spines in Horses
In a 2011 study conducted in private practice, Tracy Turner, DVM, Dipl. ACVS, Dipl. ACVSMR, evaluated 310 horses with clinical signs of back pain. He found that 68% of those horses had kissing spines visible on radiographs (X rays), whereas 39% of 70 horses with no history or evidence of back pain also had radiographic kissing spines.
Of the horses with clinical back pain, Thoroughbreds were most likely to have kissing spines, with Quarter Horse-type horses and Warmbloods being less likely. Back-sore younger horses (under the age of 5), dressage horses, eventers, jumpers, and barrel/gaming horses were all more likely to be diagnosed with kissing spines than pleasure or gaited horses. These data suggest kissing spines occurs in horses with and without clinical back pain. Therefore, while the presence of kissing spines can be considered a risk factor for back pain — it is three times more likely to be present in back-sore horses — it is important for veterinarians to correlate exam findings and case history with the radiographic findings.
Clinically relevant kissing spines can cause a range of pain or behavioral changes. Many horses show back sensitivity or soreness to the touch. Under saddle, they might buck, rear, drag their hind toes, toss the head, or kick out. More subtle signs include resistance to getting on the bit, traveling in a hollow frame or behind the leg, cross-cantering, and struggling with transitions. Riders also report discipline-specific problems such as refusing jumps or difficulty turning around barrels.
Kissing spines typically occurs in the thoracic spine, where the saddle would sit. Veterinarians most commonly find the condition from the 13th to the 18th thoracic vertebrae but have seen it as far cranial (forward) as the 11th thoracic vertebra. Occasionally kissing spines can be detected in the lumbar spine. There appears to be a hereditary component to kissing spines, but scientists have not confirmed any genetic factors beyond changes to specific regions on Chromosomes 16 and 25. Also, horses’ height seems to have a strong impact on their likelihood to have kissing spines, while sex and age seem to have less significant roles. Environmental and management factors such as saddle fit, the way the horse travels under saddle and the quality of the riding and training the horse receives could play a role, but researchers have not established definitive correlations.
Diagnosing Kissing Spines in Horses
Veterinarians can readily diagnose kissing spines using radiographs (X rays) of the back. Physiologic imaging techniques such as thermography and nuclear scintigraphy (bone scans) can help determine if inflammation or active bony remodeling accompanies the radiographic changes. To assess whether kissing spines are clinically relevant or cause for concern, practitioners should combine imaging results with a clinical exam and the horse’s history.
Many prepurchase exams include radiographs for kissing spines. It is important to remember that — especially in Thoroughbreds — kissing spines is a common finding even in horses without back pain. When veterinarians identify the condition during a prepurchase exam in a pain-free horse, they have no reliable method to predict if it will become a clinical problem in the future.
Radiograph showing typical kissing spines (black arrows)
Photo courtesy Dr. Tracy Turner
Treatment of Kissing Spines in Horses
In a horse diagnosed with kissing spines that exhibits clinical signs, treatment depends on the severity of the signs, pain and lesions seen. Treatment involves three approaches, which veterinarians and horse owners should combine for best results: pain management, muscle relaxation and strengthening.
Pain management strategies include shock wave therapy, mesotherapy (an intradermal injection technique to help block pain transmission through the spinal cord), corticosteroid injections into the spaces between the dorsal spinous processes and chiropractic adjustments. Confirming good saddle fit can also help alleviate pain. Practitioners can address muscle relaxation using bodywork/massage, muscle relaxers such as methocarbamol and acupuncture. Strengthening exercises include work over poles (in hand and under saddle) or in an underwater treadmill, core exercises and anything that encourages the horse to move freely forward in a long-and-low frame without forcing collection.
In Turner’s study a combination of shock wave, mesotherapy and correct long-and-low exercise proved to be the most effective treatment (86% of treated horses showed good to excellent results). He reported that the shock wave alleviated pain and increased the horses’ willingness to go forward; mesotherapy improved stretching. These modalities facilitated the exercise regimen, which is the most important part of treatment. Veterinarians should consider all aspects of the horse and rider’s interactions, including quality and type of riding, discipline, saddle fit, and even other medical treatments, when determining the best treatment plans.
When medical and rehabilitative exercise options fail to alleviate kissing spines symptoms, practitioners have two main surgical options available. Interspinous ligament desmotomy is a procedure in which surgeons cut the ligaments connecting the dorsal spinous processes to relieve tension between the bones; they can perform this procedure under standing sedation.
Alternatively, a more aggressive approach consists of removing a section of bone from each of the affected dorsal spinous processes to prevent them from rubbing. This surgery involves a very long recovery with a regimented rehabilitation program. Owners who pursue it must be committed to doing the work after surgery. Both procedures can have positive outcomes if horse owners or trainers complete the rehabilitation work properly. Unfortunately, both procedures also destabilize the back, which can lead to performance or lameness issues in the future.
Many horses can do well with treatment for kissing spines and return to their previous level of work. The prognosis for success decreases in horses under the age of 5, as well as for horses with more than five vertebrae involved.
Take-Home Message
Thoroughbreds face a higher risk of having kissing spines than other breeds due in part to genetics and conformation. When a horse shows clinical signs of back pain, it is reasonable for veterinarians to consider this diagnosis. However, not all horses with kissing spines develop back pain or other behavior issues.
For horses with clinical signs of kissing spines, veterinarians can implement management strategies to alleviate pain and keep horses comfortable and even competitive. Long-term treatment success often depends on a multifaceted approach. Medical therapies and proper exercise should be the first steps before pursuing surgical options.
