Kissing spines in veterinary equine patients: Easy to diagnose, complicated to treat

One researcher found that the highest prevalence of cases of ORDSP, or “kissing spines,” in the horses he studied occurred in competitive jumping horses. (Getty Images)

Overriding dorsal spinous processes (ORDSP), commonly known as “kissing spines” in horses, has become a commonly discussed and more frequent concern among sport horse owners. Lateral spinal radiographs are increasingly included in routine prepurchase examinations specifically to provide owners and potential buyers with information about this condition. Equine practitioners are being asked to address the issue through saddle fit questions, concerns about conditioning and exercise, and inquiries about treatment ranging from pain relievers and local injections to shockwave therapy and more. Recently, a number of new surgical techniques have also been developed and implemented to address ORDSP. 

However, while problems of the equine back are considered a significant source of lameness and poor performance, “kissing spines” is only one potential cause of those problems and, perhaps most significantly, ORDSP does not cause gait alterations or problems in all horses that have it. 

Interpreting imaging results

Tracy Turner, DVM, DACVS, DACVSMR, of Anoka Equine Veterinary Services in Elk River, Minnesota, is a board-certified surgeon, a member of the American Academy of Thermology and a member of the newly formed American College of Veterinary Sports Medicine and Rehabilitation. He has long been interested in back lameness in horses and, with his unique skill set, was in a perfect position to investigate kissing spines-its diagnosis, significance and treatment. He presented some of his research at the American Association of Equine Practitioners meeting in 2011 but has continued to look at the equine spine in his daily practice. 

“Kissing spines is a radiographic diagnosis,” he says, explaining that while the condition is fairly easy to document, the actual significance for each horse is much less clear. In his original study, 4,407 horses were evaluated over seven years.1 These horses were presented for lameness or poor performance, and back pain was identified in 310 (7 percent) during clinical examination. Seventy horses that had never shown any signs or history of back pain were also examined, and all horses in both groups had their backs radiographed. Of the horses with clinical back pain, 212 (68 percent) had a diagnosis of kissing spines on the basis of radiographs alone, but 27 (39 percent) of the horses without back pain history had the same radiographic diagnosis. 

A lateral spinal film from one of the author's patients. This horse is sound and in work (as an upper level jumper) without any clinical issues with its back or its performance. The dorsal spinous processes are in alignment with relatively equal spacing. The roughening on the tops of some of the processes can be normal. (Photo courtesy of Dr. Kenneth L. Marcella)

“The presence of ‘kissing spines' alone is not necessarily cause for concern but should be considered as a predisposing factor for back pain,” Turner concludes. 

His view is echoed by other researchers as well. In a collaboration between the Norwegian School of Veterinary Sciences in Oslo and the Swedish University of Agricultural Sciences in Uppsala, researchers examined 33 riding horses without any history of lameness issues or clinical evidence of back problems.2 They too found numerous abnormalities in the backs of these apparently “normal” horses using both radiography and nuclear scintigraphy. 

Their findings included increased radiopharmaceutical uptake, sclerosis, radiolucencies and abnormal spacing of the spinous processes. Only seven of the 33 had no evidence of any type of irregularity in the thoracolumbar spine. These researchers ended their study by saying, “The findings of a wide spectrum of scintigraphic and radiographic changes [among this population of normal horses] leads to the conclusion that changes within this range found in affected horses cannot be interpreted as clinically significant.” 

Evaluating clinical signs

Most of the horses that clinicians evaluate for back pain present with fairly similar clinical signs despite their wide range of eventual diagnoses. Those signs can vary from overt lameness to subtle indications of avoidance and resistance. These horses are generally back-sore to touch and may refuse to accept the bit, preferring to travel with their heads up or their backs stiff, dropped and not rounded. Some may be slow to warm up when worked or unwilling to bend in one direction. Others may not take the correct lead when directed or may cross-canter. Many riders remark that their horse feels “disconnected” from front to back. 

In these horses, signs can progress to rearing, bucking and even attempting to avoid any type of saddle or rider pressure on their backs. Many horses are eventually diagnosed with hock problems, hip or pelvis problems, or any number of conditions that cause compensatory back pain. In horses with back pain, it is imperative that clinicians evaluate the entire horse and that the back pain be clearly defined as a primary or secondary problem.

Turner's research showed a statistically significant overrepresentation of primary back pain in young thoroughbreds (less than 5 years old) and in dressage horses. Leo Jeffcott of the Equine Research Station of the Animal Health Trust in Newmarket, England, found that the highest prevalence of cases of ORDSP in the 443 horses he studied occurred in competitive jumping horses (39 percent).3 

Turner speculates that since the discipline of dressage requires that the horse progressively use its back and hind end to perform collection and lateral movements, it predisposes some horses to problems. “During training and competition,” he says, “the horse may overuse its back resulting in inflammation and pain at the sites of spinous impingement.” 

The most common site of those problems is at T15 or the anticlinal vertebrae. This site is where the angle of the dorsal spinous processes changes orientation and where increased rotational motion of the spine is possible. This area is also commonly just under the rider's saddle and the site of most contact and concussion, which may account for the high percentage of ORDSP problems noted in jumping horses. 

In Turner's study, 191 of the 212 horses had problems with this particular spinous process, and the more processes involved (going cranially and caudally from T15 and ranging from a single process to five or more), the worse the back pain experienced by those horses. All horses in the control or nonaffected group that showed radiographic changes of kissing spines but no lameness problems had those changes at T15 as well. 

Veterinary researchers and some prominent trainers are investigating a number of ideas as to why ORDSP is centered at this spot and what that might mean for treatment and-more importantly-for prevention. Jean Luc Cornille has competed internationally in dressage, steeplechase, stadium jumping and three-day eventing and he has collected numerous medals in those disciplines. He has founded Science of Motion, an organization dedicated to applying the latest biomechanical research in ways that redefine traditional approaches to equine training. 

“Kissing spines,” Cornille says, “develop from an incorrect combination of lateral bending and transversal rotation.” Though many riders may not want to hear his views, he stresses that “the solution [to kissing spines] is to create new and adequate locomotor patterns, which can only be done with the horse in motion. Basically, competent equitation is the horse's best therapy.”4

Turner believes that horses are not born with kissing spines. He told me, “I have radiographed the backs in a significant number of neonates and have not found evidence of ODSP at that age.” Consequently, predisposing conformation coupled with specific use and inappropriate riding technique may be the contributing factors to development of the condition. 

A normal thermography scan of a performance horse's back. This 11-year-old warmblood has been an upper level jumper with no history of back problems or performance issues. The scan shows a thin area of increased heat (white linear strip along the midline) and symmetric heat (red area) throughout the rest of the back. (Photo courtesy of Dr. Kenneth L. Marcella)Turner used his thermography skills to evaluate the horses in his back pain study and found this imaging modality to be “the most useful diagnostic test to differentiate ‘kissing spines' cases from other causes of back soreness prior to radiology.”1 Kissing spines was suspected whenever specific thermal or heat patterns were observed. Horses that showed a “hot streak” perpendicular to the thoracic spine, a “cold streak” perpendicular to the spine, or a combination “hot spot-cold streak” pattern over the back were much more likely to show evidence of kissing spines when radiographed. Turner states, “The positive predictive value of the thermal patterns for ‘kissing spines' is 91 percent, which is a much stronger indicator in comparison to pain on palpation in the thoracolumbar region.” 

A thermography scan from a horse with a complaint of poor performance and back pain. The linear white transverse stripes are associated with the impinging areas of the affected spinal processes. These thermal patterns are associated with a 91 percent predictive value for kissing spines. (Photo courtesy of Dr. Kenneth L. Marcella)Again, other researchers agree. Doutor Fonseca and a group of researchers from the Surgery Service for Large Animals of the Veterinary and Animal Sciences Faculty of the Sao Paulo State University in Sao Paulo, Brazil, also investigated the use of thermography in the diagnosis of back pain in equine athletes.5 They found the same types of hot spots and cold streaks described by Turner and concluded, “Thermography presents a great potential as an auxiliary in back pain diagnosis because it quickly reveals the presence or absence of alterations in this region, whether inflammatory or degenerative.”

Assessing treatment options

Once a diagnosis of ORDSP is made, there are a number of treatment options available to horse owners ranging from simple saddle fitting to invasive surgery. In Turner's study, saddle fit showed a moderate to better improvement in the performance of horses diagnosed with kissing spines in 21 of 29 horses. Some owners elected to have the affected spinous process in their horses' backs injected with corticosteroids. Fifty-five percent of horses treated in this way showed good to excellent results. 

The majority of horses in that study were treated with a combination of shock wave therapy, mesotherapy and exercise (SME therapy). Shock wave therapy was performed to reduce the pain associated with impingement at the spinous processes while mesotherapy was performed to help with nerve-related pain and allow better stretch through the back muscles. Exercise was added to further help with stretch and range of motion. These components on their own were shown to be less effective than the multimodal SME approach, which showed good to excellent results in 86 percent of horses that underwent the therapy. 

Turner states that “the most important aspect of any treatment regimen was the exercise program,” and the exercise must achieve the goal of the horse moving freely forward in a relaxed frame. It is imperative that the rider not force collection at any time. “If this goal was not achieved or attempted,” he adds, “therapy simply failed.”

More recently a number of aggressive surgical procedures have been developed to address the problem of kissing spines. Some procedures report resection of the dorsal spinous processes using an oscillating saw. Drs. Walmsley, Pettersson, Winberg and McEvoy of the Liphook Equine Hospital in Hampshire, U.K., report on long-term follow-up with 209 cases treated with this technique and found that 72 percent of these horses returned to full work.6 Another study from the Department of Veterinary Clinical Science and Animal Husbandry, the University of Liverpool, South Wirral, U.K., used an endoscopic approach to remove selected dorsal spinous processes and to resect the interspinous ligament between these processes in 10 horses.7 Their follow-up evaluation showed that nine horses had no complications and returned to full work within eight weeks of surgery. 

Dr. Richard Coomer of Cotts Equine Hospital in Narbarth, U.K., has pioneered another surgical technique that is markedly less traumatic. He performs an interspinous ligament desmotomy (ISLD) in the standing, sedated horse. “The pain from ‘kissing spines,'” according to Coomer, “comes from nerve endings where the interspinous ligament is attached to the bone.”8 Tension and pull on the ligament from exercise and the demands placed on the horse's back in various disciplines cause reflex muscle spasms that pull the spinous processes even closer together and worsen the condition. “By cutting the ligament [between the spinous process],” explains Croomer, “the nerve stops being stimulated and the horse experiences a profound improvement in perceived pain.” 

In his procedure, Croomer makes a small vertical incision on one side of the affected dorsal spinous process and a Mayo scissors is used to cut the interspinous ligament. Horses are hand-walked for four weeks followed by lunging and turnout, and they return to under-saddle work in eight weeks. Coomer compared his technique with cortisone injection therapy and reported that 89 percent of horses (34 of 38) treated with injections initially resolved signs of back pain compared with 95 percent (35 of 37) treated surgically. The significant finding was that back pain recurred in 19 of the injected horses and none of the surgically treated cases, making ISLD 24 times more likely to produce long-term resolution of signs of back pain. These surgical techniques and their refinements are a promising future for the treatment of ORSDP in horses.

Summary

In conclusion, kissing spines is relatively common in both back-sore and normal horses. Its mere presence does not constitute a problem for individual horses, but it should be seen as a possible predisposing factor for future concern. Issues varying from saddle fit to rider technique and exercise regimen should be carefully evaluated and monitored to help prevent ORDSP. Correct exercise is a key element in any treatment program, and new surgical procedures may be the ultimate answer to the management of this increasingly prevalent condition.

References

1. Turner T. Overriding spinous processes (“kissing spines”) in horses: diagnosis, treatment and outcome in 212 cases. AAEP Proceedings 2011;57:424-430.

2. Erichsen C, Eksell P, Holm KR, et al. Relationship between scintigraphic and radiographic evaluations of spinous processes in the thoracolumbar spine in riding horses without clinical signs of back problems. Equine Vet J 2004;36:458-465.

3. Jeffcott LB. Disorders of the thoracolumbar spine of the horse-a survey of 443 cases. Equine Vet J 1980;12:197-210.

4. Cornille JL. Kissing spine. Science of Motion LLC. Available at: scienceofmotion.com/documents/279.html.

5. Fonseca BPA, Alves ALG,  Nicoletti JLM, et al. Thermography and ultrasonography in back pain diagnosis of equine athletes. J Equine Vet Sci 2006;26 (11):507-516.

6. 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(1):23-28.

7. Desbrosse FG1, Perrin R, Launois T, et al. Endoscopic resection of dorsal spinous processes and interspinous ligament in ten horses. Vet Surg 2007;36(2):149-155.

8. Coomer RP, 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(7):890-897.