Welfare And Safety Summit: Using Imaging To Prevent And Diagnose Injury Is Part Science, Part Art

When it comes to diagnosing and preventing injury, the job of interpreting diagnostics is as much art as it is science, according to Rood and Riddle Equine Hospital diagnostic imaging expert Dr. Katie Garrett.

Garrett reviewed common injuries of the fetlock  in the first of a series of webcasts held this week in place of the Welfare and Safety of the Racehorse Summit, along with a quick review of the imaging technologies available for diagnosis.

(Paulick Report contributor Denise Steffanus did a survey of the different modes of imaging in 2018. You can access it here.)

Garrett said there is not yet an imaging modality that is inexpensive, quick, portable, detailed, and does not require general anesthesia – with most, you get four out of the five parameters, maximum. Radiography and ultrasound meet all of these qualifications except for the high level of detail, which is more readily available in more complex technologies like PET and MRI, which is why they’re used as a first-round screening tool when a horse is lame. MRI and PET scans provide much more detailed information, but cannot be taken stallside. PET scans on horses are also comparatively new and veterinarians are still learning about the best contexts to use them. Sometimes, the complexity of a more detailed image like MRI, PET, or bone scans lies in the interpretation.

Garrett stressed that while these technologies can give provide information about what’s going on inside a horse’s leg, there’s still a lot of individual variability to the way the horse handles it.  She used POD, or palmar/plantar osteochondral disease, as an example.

A horse’s skeleton undergoes a constant cycle of overstress/over-repair as part of the training process, which is what prepares it for the horse’s athletic activity. Garrett urged the audience to think about the bone as a living thing; the bone experiences stress and adapts to that level of stress, so as to avoid being over-stressed next time. This process is present in any mammal at any age.

POD happens when there is overstress just below the bone surface at the bottom of the cannon bone, about where it joins with P1 and the condylar bones. If the bone doesn’t have time to repair that overstress, it will begin to experience necrosis, or tissue death, in that spot. This can be a real problem, since this is the part of the joint that takes a significant amount of force when the ankle flexes and the horse puts its foot down in a gallop stride. Eventually, this area can fracture.

When POD is caught early, the horse can usually recover well after a period of turnout. If not, there is more likely to be arthritis at the site of the fracture.

The nice thing about MRI and CT images is they can show cross sections of the bones in more three-dimensional way than a radiograph can. They can show a horse that’s in the early, pre-fracture stages of POD, and they can show a horse whose ankles are responding appropriately to training, with some microdamage that is in the process of repair.

The trouble is, those two images can look very much the same.

“As a whole, the changes are good – that’s what trains the bone,” said Garrett. “One of the things that’s really frustrating is that there’s really no clear answer as to when the bone isn’t keeping up and when those changes cause lameness. There is a ton of individual variation in the middle. You can’t just look at a set of images and say, ‘This horse can keep training and this horse needs a break.’ It’s definitely not that simple.”

This is why Garrett says veterinary science has not yet arrived at a place where a horse could be scanned routinely as a means of preventing injury – some types of imaging technologies may fail to adequately highlight a problem. Others may show bone changes or activity which may be a normal part of training adaptation, rather than a buiding problem.

“The changes that we’re looking for, they’re really subtle. It takes a fair amount of experience to know, what does this finding mean in general and what does it mean to this horse,” she said. “That’s part of why there’s not just a science but an art to veterinary medicine.”

“The other frustrating part is you can have two images from two different horses that look very, very similar and one horse will be lame and one horse will be totally sound. Again, that’s some of the art – not all horses respond the same way to training and what we ask of them.”

The next webinar in the Welfare and Safety Summit series will include a panel of veterinarians discussing the importance of transparency in medical records and monitoring of horses between starts. The webinar will be held May 19 at 2 pm EST. You can access that discussion at this link: zoom.us/j/96557992970

The post Welfare And Safety Summit: Using Imaging To Prevent And Diagnose Injury Is Part Science, Part Art appeared first on Horse Racing News | Paulick Report.

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