Foot X-rays – how they can help your horse, farrier and vet
How do they work?
To first understand the concepts around the use of x-rays in the horse, lets have a quick chat about how x-rays work. X-rays were invented by Professor Wilhelm Conrad Roentgen in 1895. X-rays are electromagnetic radiation similar to light however have a much shorter wavelength. This shorter wavelength allows the x-rays to pass through materials. Materials that have a low density such as tendons, ligaments, skin and the hoof capsule allow x-rays to pass through. Materials that have a high density such as bone and metal don’t allow x-rays to pass through.
The x-ray machine is made up of an x-ray generator and a plate. X-rays are shot out of the generator, towards the plate, and the plate interacts with the beam. As mentioned before, low density materials allow the x-rays to pass through and hit the plate, whereas high density materials stop the x-rays from hitting the plate. When the x-rays touch the plate, it turns black. When the x-rays don’t hit the plate, it stays white. This is why bone and metal appears white on an x-ray, the beam cannot go through the bone/metal and hit the plate.
X-rays are a form of radiation and can cause ill effects to humans. It is important to take the correct precautions when involved in the x-ray process. Lead gowns, thyroid protectors and gloves are worn to reduce the exposure of scattered x-ray beams. Other equipment for holding the x-ray generator and plate are also used to reduce exposure.
Why are x-rays helpful and what can we see?
Bones can be reliably assessed
X-rays are very useful when imaging the foot. As mentioned, we can clearly see the boney structures within the hoof capsule such as the pedal bone, navicular bone and the short pastern bone. We can assess the health of these bones through their appearance on x-ray. Some of the diseases that can be identified on x-ray include; pedal, navicular and pastern bone fractures, bone infection and inflammation, degenerative bone diseases such as navicular syndrome and coffin and pastern joint osteoarthritis (also known as low and high ringbone, respectively).
Biomechanics of the lower limb can be estimated
One of the major reasons to x-ray the foot is to assess the biomechanics of the lower limb. This can be achieved by assessing the alignment of the pedal bone with the short and long pastern bones. We can also determine the inherent conformation of the foot, i.e. either a long toe-low heel foot or an upright/club foot. Not every foot is identical, even within one horse, therefore x-rays can help us determine the differences between them.
Hoof health can objectively be measured
The other major reason to x-ray the foot, is to help assess hoof health. Hoof health is very difficult to objectively measure.
What is hoof health? Is it hoof wall quality? Is it how fast the hoof grows? Is it the hoof pastern alignment or symmetrical hoof shape? So many questions!
X-rays can at least tell us the position of the pedal bone within the hoof capsule. From there we can estimate hoof growth rates in different areas of the foot. For example, the club foot tends to grow more heel and less depth under the tip of the pedal bone.
When should we use them?
X-rays can be used in many different cases. The obvious time is when the horse has a foot related lameness. This may be determined by the history, clinical signs and/or other diagnostics. Obtaining foot x-rays in these cases is invaluable. Common foot related lamenesses that would benefit from radiographs are laminitis, caudal heel pain, long standing abscess, suspected pedal bone fracture or infection, osteoarthritis of the coffin and pastern joint. Also in injuries to the soft tissue structures of the foot, such as the deep digital flexor tendon, navicular bursa, navicular suspensory apparatus and the collateral ligaments of the coffin joint. In cases of soft tissue injury, it helps to guide the farrier on the inherent conformation of the foot and allows to assess what changes can be made to the hoof to optimise healing of the injury.
Once a diagnosis has been reached and initial foot x-rays are obtained, immediately post shoeing images can be taken. This can help show how the biomechanics of the foot has changed after shoe application. It can also enhance the farriers ability to manipulate a foot to achieve a particular outcome. Follow up x-rays at the end of the shoeing cycle can also be taken to assess how the foot has responded to the shoeing plan.
Foot x-rays can be taken in healthy horses with no lameness issues. This is important as a baseline. By doing this it can help to prevent any issues from occurring or a drift in the conformation of the foot.
Who can take x-rays and who can interpret the images?
In Australia, people with a current radiation licence can operate an x-ray machine. This includes veterinarians, nurses and technicians. Regulation on who can take x-rays is important for human and animal health and safety.
In terms of interpreting the x-rays and making a shoeing plan for the horse, it should be a team approach between your farrier and veterinarian. The veterinarian has the knowledge and skill set to assess the x-rays from a bone and soft tissue structure point of view. On the other hand, the farrier has knowledge in terms of the biomechanics of the lower limb along with the skills to manipulate the hoof and apply a orthotic. When the two professions do not come together is when issues arise. If the farrier is interpreting the x-rays alone, this has implications from a diagnostics point of view. Similarly, if the vet in interpreting the x-rays alone, they may not have the skill set and knowledge to best determine an appropriate shoeing plan for that particular horse.
If you are thinking about having your horse’s feet x-rayed or have already done so, check out our online consulting service
Video of hoof measurements
Check out the below video on different measurements that can be obtained through foot x-rays