CT for Equine Limb Fracture Diagnosis? (AAEP 2012)

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Originally published on TheHorse.com

A fracture can put a horse's athletic future--sometimes even his life--on the line, and basing treatment on a complete and accurate diagnosis can make a major difference in the horse's recovery. A veterinarian in Belgium believes computed tomography (CT) offers a better option for imaging some lower limb fractures than radiography.

At the 2012 American Association of Equine Practitioners convention, held Dec. 1-5 in Anaheim, Calif., Casper Crijns, DVM, presented a study comparing radiographs and CT--which can provide detailed 3-D images of bone and damage within it--for diagnosing equine distal limb fractures.

Crijns, a researcher at the Ghent University Faculty of Veterinary Medicine, in Belgium, said that veterinarians often use radiography as a first-line diagnostic modality when they suspect limb fractures, but they must assess several different views to make a diagnosis. Superimposition (anatomical structures overlapping each other in a two-dimensional image) and fracture complexity can complicate diagnosis. Crijns says in his experience, bone damage is often underestimated when evaluated radiographically.

On the other hand, he said, CT creates cross-sectional images of the limbs (allowing a 3-D evaluation), which eliminates the superimposition problem and allows the veterinarian to see the fracture better. In most cases, practitioners must place horses under general anesthesia for CT, and they can only evaluate the head and limbs with this modality because of unit size.

To compare the two modalities, Crijns and colleagues conducted a retrospective study involving 27 horses with suspected lower limb fractures and three control horses. All animals underwent both radiographic and CT exams. Four observers evaluated a variety of fracture characteristics with each modality, and the research team evaluated intermodality (IM, consistent among modality) and interobserver (IO, consistent among the group of evaluating veterinarians) agreement levels statistically.

Veterinarians were able to:

• Detect and localize fractures (determine exact physical location) consistently with "very good" IO agreement levels on both radiographs and CT, but they were able to find fractures with CT that they missed on radiographs (showing "moderate" IM agreement);
• Detect fracture displacement consistently using both modalities ("good" IM and IO agreement);
• Detect joint involvement and fracture comminution (breaking into multiple smaller fragments) and identify the number of fragments consistently, but all "boardered on the lower levels of good agreement" with CT showing a slightly better IO agreement; and
• Determine fracture orientation and width and identify coalescing cracks (numerous smaller cracks that form before a single dominant crack is evident) with "poor to fair IM agreement levels," meaning results were inconsistent between radiograph and CT results, while veterinarians' evaluations were more consistent with CT than radiography ("IO agreement levels were clearly higher").

"Being able to visualize a presumed fracture or fissure is important, and accurately describing the fracture characteristics is necessary for a proper diagnosis and treatment," Crijns said.

"If a CT scan is available, I would always recommend a CT for a fracture diagnosis," he continued. "In my experience (and) opinion the extent and severity of a fracture is often underestimated on the radiographs. If a surgeon encounters additional lesions during surgery, he or she will need to adapt or completely change his or her surgery plan and this will prolong the surgical intervention and general anesthesia time.

Crijns said the resources (both time and money) needed to carry out a CT scan "will be recovered by a shorter surgery time and less complications afterwards. And due to the accurate diagnosis, better treatment is possible, which leads to a better prognosis for the horse."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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