September 3, 2020
As performance horse owners, we can be hyper-aware of pain or lameness in our horses. When they start to show pain, the symptoms can start out small—your horse starts to dip their back when you curry them and pins their ears when you cinch the saddle. Later on, they may bolt when you cue for canter transitions and explode into a bucking bronco.
These are just some of the symptoms associated with kissing spine, known in the veterinarian and equine health community as overriding dorsal spinous processes. Other clinical signs of lumbar or thoracic impingement can include failure to maintain gait and lead, cross-firing in the hind end, painful withers, or cross-cantering. Another sign is hollowing of the back when being brushed and pain upon palpation of the back and spine. Your veterinarian can provide a diagnosis of kissing spine after reviewing radiographs of the horse's back. Thermography and a bone scan can offer further information.
While kissing spine was once a career-ending diagnosis for performance horses, veterinary medicine has made great strides in the last 15 years, and more horse owners are seeking surgery to correct the condition. Before the surgical procedures, horse owners had to rely on treatment options such as corticosteroid injections, acupuncture, chiropractic, anti-inflammatories, muscle relaxants, physical therapy, mesotherapy, and shockwave therapy to help give affected horses some relief from the pain that can be associated with kissing spine.
Symptoms of kissing spine can include pinned ears when cinching the saddle, hollowing their back when being brushed, pain upon palpation of the back and spine, bolting when cued to canter, failure to maintain a gait or lead, cross-firing in the hind end, and switching leads while cantering.
What exactly is kissing spine?
Kissing spine occurs when two or more bony projections at the top of the vertebrae (dorsal spinous processes) touch or overlap. It is a common cause of back pain and back problems in thoroughbreds and warmbloods.
How do you treat kissing spine?
There are currently two surgical intervention modalities available to correct kissing spine. The first, called a bone shave procedure, is designed to remove and shave down some of the bony spinous processes, as well as clip the ligaments, to allow more room and movement for the vertebrae. The second procedure is called an interspinous ligament desmotomy, more commonly referred to as a “lig-snip.” This procedure involves cutting only the ligaments connected to the affected spinous processes, allowing the spine to relax. While the bone shave procedure is more invasive and can result in a longer recovery and rehab, it has a higher success rate than the lig-snip procedure.
Two X-Rays show a horse's "kissing spine" before having surgery vs. after having surgery. Image courtesy of Bethann Coldiron.
Cliff Honnas, DVM, DACVS, lead veterinarian and owner of Texas Equine Hospital in Bryan, Texas, has been performing the bone shave surgery for more than 10 years.
“Kissing spine involves one or more spaces between vertebrae that are either touching each other or overlapping,” Honnas said. “Nobody knows what causes it. A group of people in Europe think it is caused by horses being ridden too early, but I have started to x-ray some yearlings at a local farm and one of those already has it. So, I don’t think it is caused by trauma. It could be genetic or just the way they are born.”
Honnas has seen cases of kissing spine in performance horses of all disciplines, including dressage horses. Typically, the first sign of kissing spine will involve poor performance caused by pain. A weak topline and conformation is also a good indication that a horse may have the condition.
“They dread what I perceive is pain, and it affects their behavior and performance,” Honnas said. “A barrel horse could turn left but they can flex right. Those vertebrae will pinch and then you’ll see a reaction. Sometimes pleasure horses will switch leads while cantering, left, right, left, right, just trying to get comfortable.”
Moreover, Honnas said that in some cases a horse could be owned by the same person and competed in the same discipline for many years before showing any symptoms of kissing spine. Then, one day something triggers the back pain response in the horse, and issues will arise. “It’s not like the kissing spine just showed up, it’s been there a while,” he said.
Bethann's horse during surgery for kissing spine
The only way to accurately diagnose kissing spine is through x-ray. Though the numbers have not yet been backed by clinical study, Honnas predicts 20-30% of horses have some sort of kissing spine. He once operated on a horse that required ten vertebrae to be shaved down. However, just because an x-ray comes out positive for kissing spine, that does not always mean that the horse will exhibit pain. Honnas sees this frequently in pre-purchase exams.
“Less than one percent of horses will present symptoms,” he said. “We see a lot show up on pre-purchase exams with radiography of the horse's spine. That then creates a problem because the buyer can see the x-ray, I can see the x-ray, and then try to predict if the horse will be bothered—there is just no way to predict if the horse will have issues down the road. It’s up to the buyer if they want to take a chance on that horse.”
Honnas certainly did not predict that he would go on to specialize in kissing spine surgery. He did his first kissing spine surgery in the early 2000s after a calf horse came into the clinic presenting pain and poor performance. After performing multiple diagnostic tests with no clear answer, Honnas decided to x-ray the horse’ back.
“Sure enough the horse had kissing spine and the owner said, ‘well, fix it!’ I said, ‘I’m not sure if we can,’ so I started reading some literature and I found out they had been doing the surgery in England for quite some time,” he said. “I talked to some surgeons there and decided to give it a whirl, and the owner was on board, and it worked.”
That first surgery caused Honnas to dig deeper on horses who were presenting pain and poor performance but weren’t able to pinpoint it to one cause. Soon, taking an x-ray of the back became a regular diagnostic tool when all else failed. “It just kind of snowballed from there, and it became another after another. I’ve probably done 800 surgeries now,” Honnas said.
Bethann's horse post-surgery for kissing spine.
If surgical treatment is an option for the horse and owner, Honnas will perform the bone shaving surgery. He prefers this procedure to the “lig-snip” procedure for severe cases because he believes it is more efficient and will have a better chance at completely curing the horse. It is, however, a bloody surgery due to the vascular location of the area to be cut. A horse owner should be prepared for extensive rest and rehab. After the surgery, a horse will usually stay at Honnas’ clinic for two to five days before they are released to go home. Stall rest is typically about two weeks followed by hand-walking and turnout in a small area.
“Depending on how many spaces I have to operate on, a horse with one to three spaces are typically being legged up in 60 days,” Honnas said. “If it is four or more spaces, it is a minimum of 90 days of rest, and then more spaces than that, [it’s] at least four months. A lot of it is just letting those muscles heal that we have to cut to get in there. Using an aqua-tread can be beneficial to rehab for warm-up.”
“Saddle fit is also very important. You want a saddle that is as close to a perfect fit as possible. You don’t want anything that will be too narrow and pinch. I don’t recommend a treeless saddle because it concentrates too much pressure on one part of the back. You want something that disperses pressure evenly. A horse owner should at least take their saddle to a custom saddle maker and have their saddle evaluated.”
Of the bone shaving procedures he has performed, Honnas said that about 90% of horses make a full recovery with an improved range of motion. In some cases, he said, some horses will still experience some pain and you will never get to the bottom of what is hurting them.
“I won’t ever say that the surgery is 100% successful because you’ll always have those horses who will still have something nagging them and you can’t attribute it to anything. You just can’t ever figure it out,” he said. “And that is very frustrating to me as a veterinarian because I want to help these horses and owners.”
Post-surgery, giving their back some level of fitness before returning under saddle is very important. It gives them a jump-start before they go back under saddle again. Using a Pessoa balance training system, lunging, stretching and pole exercises have also been proven to be beneficial to a horse being legged up after kissing spine surgery.
Some equine rehab centers specialize in the after-care of a horse who has had kissing spine surgery, such as Equi-Care in Lampasas, Texas. Working closely with the veterinarian who performed the surgery, Equi-Care’s staff formulate a rehabilitation plan that fits the needs of each horse.
“Our main job is to fill a prescription, so to speak,” said Cody McCorkle, manager of Equi-Care. “They most all have the same protocol but we may tweak it depending on who did the surgery. After that horse has completed 30 days of rest, they will typically come straight to us. We have an underwater treadmill. They will go on that every day for 30 days, and after the 30 days, they will get rechecked. If everything looks good, we increase the time on the underwater treadmill, and they will also start on our equiciser for 15 minutes and we will gradually increase the time and level of work.”
McCorkle said giving their back some level of fitness before returning under saddle is very important. I think it gives them a jump-start before they go back under saddle again. Using a Pessoa balance training system, lunging, stretching and pole exercises have also been proven to be beneficial to a horse being legged up after kissing spine surgery.
Equi-Care has rehabbed 20 horses post-kissing spine surgery in the last six months, McCorkle said. In the last year, they have seen a spike in the number kissing spine horses that receive after-care at the facility, and McCorkle expects that number to rise even more.
“I think more horse owners are deciding to have the surgery done because the technique used in both surgical procedures has improved,” McCorkle said. “It is usually a happy ending for both the horse and the owner.”