Years of experience has taught us that early, safe and accurate diagnosis is paramount when your horse falls lame. The imaging method of choice in human medicine for many years, MRI offers the same diagnostic capabilities for equine limbs and is considered the gold standard for diagnosing orthopaedic conditions. Proved to be diagnostic in over 90% of cases, Hallmarq’s Standing Equine MRI offers a unique insight into equine lameness.
Why would my horse need MRI?
Often during a lameness workup, your vet will use nerve blocks to locate the area of pain. This may then be followed by x-ray or ultrasound examinations. However, x-ray and ultrasound present a limitation in their ability to assess the limb as a whole. MRI not only allows complete evaluation of soft tissue and bone simultaneously but provides an extremely high level of detail of all structures, enabling more subtle lesions to be clearly visualised where x-ray and ultrasound would fail to identify any problem.
How does MRI work?
Your horse is walked into the MRI scanner, and the lame leg placed between the poles of the magnet. A radiofrequency coil is fitted around the injury site and the operator makes careful adjustments to ensure that both horse and magnet are in the right place. Radiofrequency waves are used to assess changes in the position of hydrogen atoms within the body tissues when minor adjustments are made within a strong magnetic field. These changes are interpreted and used to create the images. The magnetic field or the radiofrequency waves are not harmful to your horse or people. MRI is an extremely safe diagnostic imaging modality.
Does my horse need to travel to have MRI?
Yes. MRI equipment is specialist and importantly requires housing in a shielded room to prevent electrical interference distorting the images as they are acquired. Something as seemingly insignificant as a phone receiving a text message near the equipment can result in a non-diagnostic image. MRI scanners are therefore not portable and require the horse to travel to site.
Why do the shoes need to be removed?
In most cases, just two shoes are removed, on the leg to be scanned and the adjacent leg. This is for two reasons; firstly, any metallic objects distort the image and secondly steel shoes could become stuck to the magnet.
Why does the horse need to be sedated?
Even the most docile of horses will sway or move slightly when standing and this movement changes the shape of the joint as the horse shifts its weight distribution. As the horse needs to stand as still as possible throughout the process, sedation helps to ensure this and, if necessary, will be topped up. Hallmarq’s award-winning motion correction software has been designed to better manage these slight movements and improve the resolution of the final images.
How long does MRI take?
An MRI scan usually takes between 1-2 hours and produces around 300-500 images of the limb or hoof taken from multiple angles. Your MRI Operator will have been trained and certified by Hallmarq to capture the highest quality images.
Who looks at the images – will it be my vet?
The images are carefully reviewed by the vet responsible for the scan, to arrive at an opinion on likely conditions or injury. These findings are sent to your own (referring) vet for review with yourself within around 48 hours.
Why does my horse need x-rays beforehand?
When scanning the feet, each foot is radiographed first to check that no tiny pieces of clench remain within the hoof.
What does MRI diagnose?
MRI is most frequently used in cases where lameness has been localised to a specific area of the limb using nerve blocks, but where other imaging modalities such as X-ray and ultrasound are unable to confirm the diagnosis. It is particularly useful for imaging the soft tissue structures within the foot, as ultrasound cannot penetrate the hoof capsule. It is the only modality able to distinguish between the 12 different conditions of navicular disease and can detect bone damage up to 3 weeks before changes can be seen on X-ray.
Why is it better than x-ray and/or ultrasound and/or CT/other imaging modalities?
No single imaging modality gives us all the answers, and it’s important to remember that the information provided by any diagnostic imaging technique must be examined in the context of the individual patient Apart from being an incredibly safe imaging technique, however, MRI delivers a wealth of information about both soft tissue and bones. Unlike other modalities, it can see through the hoof capsule, providing invaluable information about the foot and revolutionising the diagnosis of conditions such as navicular disease and deep digital flexor tendon injuries.
What’s the difference between standing and lying MRI?
Although some level of sedation is nearly always needed, where imaging can only be done with the horse recumbent or lying down, a general anaesthetic will be required. General anaesthesia, even in a healthy horse, carries increased risk; 1% of horses suffer complications, which can be life-threatening. In addition, imaging the limbs while the horse is standing and gently sedated, allows internal structures to be assessed while they’re load-bearing, which is usually when the lameness is most apparent.
Is it the same as human MRI?
While some vets argue that the higher magnetic field of a human-type scanner gives clearer images, comparison studies have shown the images captured of horses in the Hallmarq low-field MRI scanner to be of comparable diagnostic value.
Will it hurt my horse?
In short, no – this is a non-invasive diagnostic technique. Without the need for anaesthesia, and often allowing for day patient scheduling, gentle sedation is administered via a drip or needle and topped up during the scan if necessary. An added benefit is that unlike radiography and scintigraphy (bone scanning’), MRI does not involve the use of ionising radiation, so there are no hazardous biological effects to either the horse or the vets and technicians carrying out the scan.
Is it expensive?
An MRI diagnosis is far more cost-effective than multiple rounds of the examine-treat-repeat loop, leaving enough funds to cover the cost of treatment. With a clear diagnosis, you can make the best decision for your horse, agreeing on a targeted treatment plan that gets results.
Will my insurance cover the cost?
Most UK insurance companies cover the costs of MRI. Some will ask that you cover a certain percentage of the costs and other policies might exclude certain conditions or treatments. Always check with your own insurance company first.
Why is MRI specifically useful for cases of Navicular disease?
MRI is the only modality able to distinguish between the multiple different causes of navicular disease or heel pain. Historically, navicular disease was diagnosed when abnormal changes to the navicular bone were seen on x-ray. With the wealth of additional information MRI gives us about the bones and soft tissues within the hoof capsule, we now know navicular disease or syndrome can cause foot pain due to a number of different problems. Structures such as the impar ligament and the insertion of the deep digital flexor tendon are extremely difficult, even impossible to assess without MRI. Understanding the how damage to these structures results in navicular disease has enabled vets to direct treatment more specifically and therefore more effectively in these cases.
Why is MRI of the fetlock used for racehorses?
Fast work at high speeds during both training and racing places the fetlock, particularly the back of the joint, under extreme forces. This repetitive, extreme shock absorption by the joint can lead to traumatic lesions affecting the subchondral bone and/or cartilage. Whilst the lesions can be severe, horses can appear only mildly lame, ‘work out’ of the lameness or even appear sound but not performing as well as expectations. If left unchecked, these lesions can lead to catastrophic breakdown of the fetlock joint ending the racing career of an individual or resulting in catastrophic fracture and emergency euthanasia.
Although some of the more severe lesions can be seen on x-ray, often by the time they are visible, the disease has progressed. Detection with MRI, due to the superior ability to identify subtle changes earlier in the progression of the disease process, enables rest periods and training modifications to be made before clinical disease terminally affects the individuals racing career. MRI can also be used to monitor return to health of the joint before training for racing performance is resumed.