We have never really understood navicular disease, but maybe we're getting closer. Two horses would have identical lameness symptoms but the radiographs were clean on one, and clearly showed a bone lesion in the other. Some horses stayed lame for years and were never ridden again. Others took a year or so off and, to everyone’s surprise, returned to training.
Navicular disease confounded veterinarians, frustrated trainers and broke the hearts of riders and owners young and old. But as the sophistication of veterinary medicine improved, so did the accuracy of both the diagnosis and prognosis for horses suffering from what we started to call “navicular-type lameness”.
The farrier profession joined forces with veterinarians to fight the war on navicular disease. Farriers adopted the use of bar shoes, pads, impression material and complex localized combinations of hard and soft materials to support the hoof and take stress off the navicular bone, navicular bursa, deep flexor tendon, and/or the ligaments of the navicular zone. Sometimes it was a trial-and-error process. Coffin joint and navicular bursa injections helped sometimes, too, as might injectable treatments like Legend and Adequan. And then there was shockwave, vibration, acupuncture, chiropractics, changes in bedding and arena footing, joint supplements and an arsenal of medications.
But that was then.
Since the advent of standing MRI for the horse, veterinarians are able to see the inside of the foot from every angle. They are able not only diagnose the health of the navicular bone, they can evaluate the bursa, the tendon and the ligaments, and look for clues to the horse’s pain.
And when they find the source, they can accurately judge if the problem is likely to respond to treatment.
Eugenio Cillán García, LV, MSc, MRCVS
Lecturer in Equine Surgery
Cillán-García led researchers at the University of Edinburgh in Scotland, who reviewed 168 horses that had been evaluated for foot lameness that was subsequently diagnosed as being caused by a lesion or tear in the DDFT. All the horses had both front feet scanned with the Hallmarq Standing MRI unit, either at the private Liphook Equine Hospital, University of Liverpool or at the University of Edinburgh.
The authors write: “Lesions of the DDFT were divided into core lesions, dorsal border lesions and parasagittal splits. Lesion location was documented.”
|All the horses in the study were shod according to a standard set for them, using a graduated heart-har shoe. (Photo courtesy of Eugenio Cillán García)|
After 18 months had passed, owners were asked how the horses were doing.
The authors collected the owners’ statements and reported, “Of 168 horses with primary DDFT injury, 54 horses had dorsal border lesions, 59 had parasagittal splits and 55 had core lesions. Twenty-five per cent of all horses returned to previous levels of athletic activity within 18 months of MRI evaluation.
Horses with complete splits or core lesions of the DDFT were significantly less likely to return to some level of athletic activity than horses with dorsal border lesions . Dorsal border lesions of the DDFT appear to have a better prognosis than core lesions or parasagittal splits.
|Hallmarq infographic compares the route to recover for horses diagnosed with and without MRI to back up the diagnosis.|
The authors concluded that injury to the deep digital flexor tendon is still a serious threat to a horse’s athletic future but that by using MRI to pinpoint both the location and severity of the injury it may be possible to give owners an accurate picture of what the horse’s future may hold.
An important fact that emerged from the study was that horses that were referred for MRI within 0–8 weeks of onset of lameness, had a significantly increased likelihood of returning to some level of athletic activity compared with horses referred after a longer period.
Without equine MRI, vets use the limited tools available to them to diagnose the probable cause of lameness, and prescribe treatment on this basis. In effect, they are doing it the old-fashioned way, and without the accuracy afforded by MRI.
The most common approach to lameness is to check the hoofcare, rest the horse and treat conservatively. Improvement in the condition is generally taken as confirmation of the diagnosis, but this process is only effective around 30% of the time. If the horse fails to improve the vet will investigate again in search of a different diagnosis, but often a horse will be investigated many times over before a satisfactory conclusion is reached (if ever).
The outcome of horses treated in this way varies, as the catch-all “navicular syndrome” diagnosis covers many different pathologies. Some of these injuries do originate in the navicular bone, others in structures such as the navicular bursa, coffin joint, tendons or ligaments.
Standing MRI can return clear images of each of these structures. With high quality MRI images, picturing the inside of the foot as "slices" in different planes, vets can make diagnoses with more confidence than ever before.
MRI may seem expensive, but when comparing the costs it is important to weigh up the alternative potential costs of multiple trial-and-error shoe-rest-treat cycles, and the other costs incurred through remedial farriery, extra stall rest and time off work.
To learn more about Hallmarq Veterinary Imaging and standing MRI technology for horses:
- "Like" Hallmarq Equine MRI Facebook page;
- Follow @HallmarqMRI on Twitter;
- Subscribe to the hallmarqvetimaging channel on YouTube.com;
- Watch for a growing equine distal limb Hallmarq MRI image gallery on Flickr.com.
- Visit the Hallmarq.net web site. (Plan to spend some time there!)
© Fran Jurga and Hoofcare Publishing
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Disclosure of Material Connection: The Hoof Blog (Hoofcare Publishing) received direct compensation for writing and posting this article. Hoofcare Publishing has no other material connection to the brands, products, or services mentioned, other than products and services of Hoofcare Publishing. I am disclosing this in accordance with the Federal Trade Commission’s 16 CFR, Part 255: Guides Concerning the Use of Endorsements and Testimonials in Advertising.