Though many experts believe magnetic resonance imaging (MRI) is underused in equine veterinary medicine, greater availability
of the technology and access to interpretation experts are facilitating greater adoption, especially when diagnosing lameness.
The integrated table at Alamo Pintado Equine Medical Center is able to hold 550 pounds, so they are able to place a portion
of the horse on the table within the magnet, allowing them to image a larger portion of the horse.
"I think the message to equine practitioners right now is that they tend to think that they don't have to worry about MRI
because they can't afford it and that it is not available," says Bob Schneider, DVM, Dipl. ACVS, equine orthopedic surgeon
at the Washington State University Veterinary Teaching Hospital. "But it is available. We're not talking about something that's
in the near future. It's pretty much in use widely right now."
MRI has exceptional sensitivity and specificity, provides physiologic and anatomic information about bone and soft tissue
and is useful to identify occult subchondral bone and soft-tissue injuries. MRI has made it possible to identify injury to
the bone, tendons and ligaments that could not previously be identified in horses.
MRI provides several sequences composed of hundreds of images in each sequence.
Sagittal view of a cushingoid horse with no macroscopic evidence of an adenoma present.
"We have been able to diagnose lameness problems we didn't even realize existed before MRI," Schneider says.
Ultrasound works for some problems but has limitations in imaging all the structures of the foot. Radiographs can detect major
bone injuries clearly, but MRI is more sensitive, provides an even clearer picture and can identify accompanying soft-tissue
injury. MRI produces a clear display of anatomy on any plane and allows for visualization of different tissue structures.
The image along with a good physical can cue clinicians into what might be significant about an animal's presentation.
Helping make a firm diagnosis
When lameness develops in performance horses, a definitive diagnosis is necessary to provide effective treatment and an accurate
prognosis. Lameness evaluations, radiographs and ultrasound are typically used to identify the cause of lameness. MRI should
be considered in cases when the lameness has been localized to the distal portion of the limb, but a definitive diagnosis
can not be made from radiographs or ultrasound, says Chad Zubrod, DVM, MS, Dipl. ACVS, of Oakridge Equine Hospital in Edmond,
Okla. The results of MRI evaluation may change the type of treatment prescribed in many cases. New and novel treatments may
be beneficial and improve the horse's prognosis for return to athletic performance.
Fractured navicular bone at the central eminence with mild palmar displacement. Increased fluid accumulation at the central
eminence is indicative of inflammation.