Kissing Spine Disease - Dorsal Spinous Impingement

Skeleton of a horse

Dorsal Spinous Process (DSP) impingement or “Kissing Spines” is a condition recognized as a significant issue for horses. What constitutes the problem is debatable and how to make a conclusive diagnosis can be an elusive process. The following article will discuss the anatomic findings, diagnostic process, therapeutic options and prognosis.

In order to understand the issues behind DSP impingement you have to understand a few anatomical factors. Generally the problem is located in the thoracic section of the vertebral column - the area where the rider sits. Less commonly, involvement of the lumbar vertebrae behind the saddle area can be the source of the problem.

As you can see with the attached picture to the left, the thoracic vertebrae begin with the withers and go through the saddle area.

Diagram of 2 Thoracic Vertebrae with attached rib. The DSP's are in a normal position, paralell to one another

The part of the vertebrae that we are interested in is the vertical part that projects up and should be evenly spaced from the adjacent process. In the following picture two dorsal spinous processes are seen with the correct relationship.

In order to understand the correct relationship between the vertebrae in the back a radiograph is the easiest way to see how the bones sit relative to one another. The following picture is of a combined back radiograph from a horse with normal spacing. The left side of the image starts with the withers and moves down the back to the right showing the lower back. The tall vertical DSP's that make up the withers are narrow and long but are usually not involved with Kissing Spine Disease; instead, it's usually the group of vertebrae behind this area - the thoracic vertebrae, in the area where the rider sits. As you can see the spacing between the DSP’s is even and there is no significant bone reaction.

The next picture is of an abnormal radiograph which clearly depicts kissing spines. As you can see the finger like spinous processes are either touching the adjacent process and in some cases actually overlapping.

DSP impingement in horse with significant back pain.

Clinical Signs

Horses with this condition can exhibit a range of signs from being asymptomatic, that is exhibiting no abnormal signs, up to having a horse that is unrideable, possibly bucking, refusing to be saddled and/or having behavioral issues even on the ground. The question isn’t understanding the more obviously affected horse; instead, it’s the asymptomatic horses. The radiographic changes didn’t occur overnight and there are certainly horses that have been in regular work during this time and able to do jump, be used for dressage and/or western pleasure while the radiographs would have looked abnormal. Something must change in order for the problem to be evident and something must change again if the problem is going to get under control.

I have heard a variety of complaints from the riders and trainers over the years associated with this condition, the most common one relates to behavior-training issues. Generally the horses may not be overtly lame, but rather exhibiting avoidance behaviors that affect their work such as: refusing to accept bit contact. preferring to travel with their heads up and their backs dropped (not rounded), unwilling to bend one direction or the other, not consistently picking up the correct lead, feeling disconnected or possibly cross cantering. Obviously these signs could be associated with a number of issues for example: stomach ulcers, Lyme disease, tack, training, rider to name a few.

Diagnosis

Making the diagnosis can be a straightforward process in some cases; in others it’s a process of elimination. The history and clinical signs are particularly beneficial to the Veterinarian. Following this Radiographs are the first line of defense. Digital x-rays allow us to take radiographs of a horse’s back in a matter of minutes and clearly see if there are issues present as seen in the image below:

Horse with back pain, reluctant to collect and move forward.

Ultrasound is also sometimes employed. Traditionally it’s been considered a great modality to evaluate soft tissues, but it’s exceptionally helpful when looking at bone surfaces. While x-rays penetrate bone and show the margins and inside of bones, ultrasound shows a significant amount of detail about the bone surface and soft tissues attached to them. What can’t be appreciated in some circumstances without ultrasound is back soreness from the ligament that runs over the spine and inserts into these DSP’s nor the ligaments that are located between the bones.

Thermography is also used by me in cases where I want to evaluate heat output which can correlate to inflammation. By using a thermal camera I can visualize areas of the back, legs and even saddle fit. The more intensely red or white areas correlate with inflammation.The following two pictures demonstrate a more normal back on the left compared to the one on the right with more inflammation in the saddle (thoracic) area as well as over the hips (sacro-iliac) areas.

Normal image with some red color indicating warmth in saddle area
 Significant heat output in saddle region + over croup (sacro-iliac area).

In cases where there are more questions as to the involvement of the back versus other areas a Nuclear Scan can be done. These are procedures done at referral hospitals. The advantage is that, like thermography, they are dynamic exams and show problems in real time as opposed to static exams such as radiographs or ultrasound that show what is currently there, but don’t necessarily correlate to inflammation.

Nuclear scan detects output of accumulated radioactive material using a camera.

Treatment

As might be expected treatments can vary. The most important concept is that regardless of the treatment, physical therapy is even more integral to a successful outcome. What I am referring to here is that the treatments can help manage the soreness short term and even for longer periods, but without instituting a modification in the riding, training and/or tack the problem may continue to affect the horse.

Generally I have found that treatment of the affected areas with injections using a combination of corticosteroids and Sarapin has been beneficial. In most cases that will be my first treatment and often done at the same time the radiographs are taken if the diagnosis is definitive.

Over the years I have treated numerous horses with Shockwave Therapy (SWT) and have also found this effective; in fact, for some horses the benefits are about the same as injections. SWT is also beneficial as a management tool, that is allowing treatment periodically and/or a short time before competitions may decrease the discomfort associated with this chronic condition.

In some of the acute conditions I have effectively used a laser to treat focal areas of inflammation. Laser treatments can treat inflammation of the bone, soft tissues and nerves.

Tildren is the newest medication that I would add to my list. Most of the research with this drug has been done in Europe and it has proven benefits for horses with kissing spines. The essential mechanism is that it decreases the bone destructive process of bone inflammation and “turns on” the bone cells that help to rebuild damaged bone. What is unique with this medication is that its role is not to mask pain, but to improve damaged bone which interrupts the destructive process and improves long term comfort. Currently I import it from France with a special permit and have used it successfully in numerous cases. While it is somewhat costly, the benefits far outweigh any negatives.

The horse below with kissing spines that was unwilling to go forward comfortably, refused jumps and would not collect well was treated with Tildren. Following treatment he was markedly improved and the results lasted longer than when just local injections were used.

Kissing spines identified in saddle region of Thoracic Vertebrae.

Alternative modalities such as acupuncture, chiropractic adjustments, mesotherapy and/or massage can also have a role here. I have used them as a first line treatment as well as in a more supportive role. In my opinion if we have a case of significant bone reaction along with kissing spines then the benefits of chiropractic may be minimal and possibly counter productive; however, acupuncture or mesotherapy can reduce the pain and dysfunction. There are a number of individuals in our area that practice equine massage and are frequently recommended by me.

Again physical therapy should be considered the essential component for management of this condition. Using exercises that help to build core strength and ones that allow the back to lift are the main concepts. Lunge work often with side reins, using a Pessoa system, belly lifts are all designed to help strengthen the back and pelvic muscles.

Horse lunged with Pessoa system

Again physical therapy should be considered the essential component for management of this condition. Using exercises that help to build core strength and ones that allow the back to lift are the main concepts. Lunge work often with side reins, using a Pessoa system, belly lifts are all designed to help strengthen the back and pelvic muscles.

When we refer to building core strength it’s not the back muscles that are over the spine but rather the ones adjacent to the spine (multifidus muscles), the ones that go from under the spine to the hips (psoas muscles) and the ones that run along the abdominal wall (abdominal oblique muscles) that we try to strengthen. These are the muscles that work to lift or flex the back versus the ones on top that extend the back.

Of course the physical therapy piece of the puzzle is easier than it sounds and may take months to fully appreciate the benefits. I find that combining it along with some type of therapy that makes the horse more comfortable is the best way to go.

Surgery - new procedure

Interspinous Ligament Desmopathy (ISLD):

This is a surgery that originated in Europe, possibly some initial work was done in France, then later further developed in England. One of the first surgeons to publish information on the procedure and results was Dr. Richard Coomer from Cotts Equine in Wales. About a year ago I contacted Dr. Coomer about some cases that seemed like good candidates for the procedure and asked his opinion. He very graciously replied, reviewed the radiographs and definitely agreed that the new ISLD surgery was appropriate for them. He offered to come over and do some cases with me and while that was appreciated, my goal is to not do surgery thus I have referred these cases to a surgeon who has done quite a few of these. In the past 12 months Dr. Jose Garcia-Lopez from Tufts University Veterinary School has been the surgeon I have referred all of these cases to and we have had excellent results.

The theory behind the surgery is described by Dr. Coomer as follows:

"The pain from kissing spines comes from nerve endings present where the ISL sticks on to the bone. Tension and pressure on these nerve endings gives the horse back pain, and causes reflex muscle spasm which pulls the spines even closer and makes it even worse. By cutting the ligament, the nerves stop being stimulated, and the horse experiences a profound improvement in perceived pain. Evidence from France originally suggested that cutting the ligament alone was the important element in successful treatment of kissing spines. We developed this and applied it to the standing horse."

The procedure is done with the horse standing and sedated and a small vertical incision is made adjacent to the involved DSP's on one side then the ISL is cut thus releasing the tension between the two opposing vertebrae. Most of the horses are sent home the next day to rehabilitate at home where they start with hand walking for the first 4 weeks, followed by a period of lunging and turn-out in the 2nd month and if there is appropriate improvement when re-radiographed at 8 weeks they are started back under saddle. So far, unless there have been extenuating circumstances, all of the horses were able to start back with a rider at that point.

Minimally affected spine showing some impingement along with 2 ligaments: SSL and ISL

In the above picture there are several vertebrae where the space between them is mildly narrowed and there is some increased whiteness in some of the edges where the red arrows indicating the ISL attach. Fortunately this horse, a Hunter/Jumper, responded well to medical management. Initially I injected between and adjacent to the affected vertebrae with steroids plus Sarapin. This worked great for the season and he jumped successfully. The following year due to other soundness conditions arising I treated him with Tildren and he had a very positive response with the multiple areas involved.

For the actual surgery, the surgeon would make a vertical incision that would transect the ISL which is depicted as the area where there are red arrows. The Supraspinous Ligament (SSL) that runs over the tops of the DSP's is still intact and that stabilizes the vertebrae.

The following two radiographs will demonstrate an actual patient that had the surgery in the summer of 2013.

This horse is an 11 year old Irish Sport Horse gelding that had been a jumper for years.

Pre-surgery see 4 spaces involved.
8 weeks post surgery

In the above images you can already see some "opening up" of the spaces between the 4 sites. Prior to the surgery this horse became unrideable as he was bucking so much and even low level jumping had become impossible. During the fall once he was started back under saddle all of that had resolved and he was able to start over low jumps and remained very comfortable.