Overriding spinous processes, more commonly known as kissing spines are more then just a pain in the back for horses and horse owners alike. They are though, probably the most common cause of back pain in horses, and with technology continuing to increase they are more easily diagnosed now then ever before. I have been involved in more then ten horse dissections and we have not had a horse on the table that has not had some presence of kissing spines, so it is more common then we think.
The spine of the horse is composed of vertebrae (attached to ribs in the thoracic region) joined together and held there by ligaments and the surrounding muscles. The part of the spine that sticks up and that we think of as the “back” is the dorsal spinous process. These are present from the firs thoracic vertebrae T1 to the last lumbar vertebrae L6. In a normal horse there is space between these spinous processes as can be seen in the image below. Kissing spines occurs when something happens to decrease this space and causes one of the dorsal processes to brush (or kiss) against another, and in the worst cases override the other process. This causes pain and inflammation and also restricts movement within the back itself.
What causes kissing spines is an open ended question that will be unique to the specific horse, but ultimately it will be something that effects the straightness and alignment of the spine. It can be purely poor conformation, secondary postural changes from other issues such as sacro iliac, hock arthritis, etc or it can be caused directly by the rider wether it be an ill fitting saddle, a rider that is too big for the horse, or riding a horse without the muscle to support it’s spine etc. The most common place for kissing spines to occur is between T13 – T16 (the 13th – 1th thoracic vertebrae) because is the region in which the spinous processes change from rear facing to forward facing, and also under where the rider sits. More often then not you will not know the cause of the issue, but that is important to try and work out when determining a rehabilitation program for your horse.
The signs and symptoms of kissing spines and vast and varied and can easily be mistaken for something else as you can read here: https://horsemassagecourse.com.au/blog/when-things-are-not-all-they-seem Some horses don’t even have any physical signs of pain associated with it, but the most common signs include:
- Discomfort under saddle
- Drops the back when the saddle is placed on
- Does not like being mounted
- Reluctance to bend under saddle
- Pain in the back when brushing or sweat scraping
- Loss of topline
- Disuniting behind
- Alteration of gait
- Back stiffness or “hollow” through the back
- Reluctance to work in a frame
- Behavioural changes – bucking, rearing, pig rooting
But these signs can be just as simple as a loss of performance. What you need to be very careful of is that kissing spines is often secondary from something else that the horse is experiencing and if your horse is diagnosed with them then it’s important the vet does a full work up to try and identify the primary issue.
It is also important that kissing spines are only diagnosed by a vet using radiology as it is important to see wether there are any other bony changes associated with the overriding processes such as loss of bone density, calcification, sclerosis, bone spurs etc. They will also want to asses how much space is remaining or not between the spinous processes.
Depending on the severity of the kissing spines there is a range of options. Obviously removal of the cause is the most important factor, but difficult if you don’t know what that is….Getting the back to a point where the pain is limited is the primary goal. Then depending on the severity the vet may recommend a conservative therapy such as muscle therapy, shockwave, mesotherapy, therapeutic ultrasound, acupuncture or cortisone injections, which is the most common form of therapy. In severe cases they may suggest surgery (shaving the bone or cutting the ligaments) but this is controversial and does not have a lot of clinical evidence available on the success.
Once treatment has been advised then a rehabilitation program should be implemented in order to rehabilitate the strength and function of the back. We will talking about this in our next blog.