When we think of the bones in a horse's body, it is hard to pick which one is the most important. Every bone has it's own role and purpose for the horse to function and move. Did you know that a horse has 205 bones in their body! Horses are very similar to humans because humans have 206 bones. In my opinion the spinal column is the most important area of the body. It is made up of 54 bones. Seven are located in the cervical section (neck), 18 in the thoracic section (body), 5/6 lumbar vertebrae, 5 sacral vertebrae (lumbar and sacral making up the hindquarter) and 15-25 caudal vertebrae (these are the tail bones, some horses only have 15 while others can have 25, the average number is 18). Each section of the spine is responsible for supporting the whole horse's body.
Individual vertebrae are shaped differently according to it's purpose. The cervical vertebrae in the neck hold up the head while the start of the thoracic vertebrae help support the muscles in the shoulder (hence why the wither is the highest point of a horse's back). Something that you may not be aware of is the strength of a horse's back and how much weight they can carry is determined by the size of the vertebrae in the lumbar region.
The spine is responsible for:
- Lateral bending
- Axial rotation
Now that you have a bit more of an understanding a horse's spine it is important that we can understand common problems. One of these issues is called 'kissing spine' or an impingement of the dorsal spinous processes. This problem occurs when adjacent vertebrae come in contact with each other. Kissing spine is very common in racehorses. This is because they are broken in at a young age, so horses that have immature and weak bones do not handle the weight and stress placed on the spine when being broken in.
Above is an example of what the spine looks like when the vertebrae are too close.
Common signs of a horse that may have 'Kissing Spine"
- Refusing to be saddled
- Avoiding owners ques (bridling)
- Head staying up in work
- Difficulty picking up the correct canter lead
- Cross cantering/disuniting
Kissing spine or overriding spinous processes (OSP) can create further issues in a horse's body. When the vertebrae start to push together the inter-spinal ligament is affected resulting in osteoarthritis. Osteoarthritis creates a loss of structure and integrity within the ligament. Weakness, pain and further behavioural symptoms can then occur. To check if this ligament has been affected ultrasound can be used to diagnose. The ligament will show thickening and there will be changes in the fibers.
A study conducted also found that horses that had OSP had fibrocartilaginous metaplasia. This is a phenotypical transformation of fibroplasts into chondrocytes with subsequent change in the matrix product which occurs as a response to chronic soft tissue irritation. Wait! what does all this mean? Well, basically when the vertebrae connects the soft tissue surrounding the spine are irritated. Sensory nerves are also significantly increased for horses with OSP. The more sensory neurons there are, the more pain the horse will have. This therefore makes them a lot more reactive to external stimuli (for example: being saddled).
So how can we help a horse is OSP? There are many therapies that can be used to improve the soft tissue and muscle structures around the spine. These include:
- Bowen Therapy
- Physical therapy
- Corticosteriod needles
If your horse has been diagnosed by a vet with OSP I highly recommend that the horse receives some form of therapy to prevent future problems.