If you’re considering a whole-body bone scan to find out if your horse’s lameness or poor performance might be due to foot pain, think again. Recent study results suggest that scintigraphy (bone scanning) might be useful in a lameness workup, but it’s not the most reliable diagnostic tool overall.
Scintigraphy can provide the practitioner with information about some injuries related to bone or soft-tissue connections to bone, but it might not reveal many other sources of foot pain, said Sue Dyson, MA, VetMB, PhD, DEO, Dipl. ECVSMR, FRCVS, head of Clinical Orthopedics at the Animal Health Trust Centre for Equine Studies, in Newmarket, England.
Essentially, if the scan gives a negative result, that doesn’t mean there’s no injury, Dyson said. And if the scan gives a positive result, that doesn’t mean it’s the only injury.
“The foot is a complex structure comprising bony structures, joints, tendons, and ligaments,” she said. “Given that scintigraphy primarily gives us information about the metabolic activity of bone, it is not surprising that it is more reliable for detection of bony abnormalities and soft tissue lesions at attachments to bone than primary soft tissue lesions.”
In their study of 70 horses, including examinations of 121 front feet, Dyson and colleagues found that MRI scans were far more likely to reveal injuries that were sources of pain than scintigraphy. The results overturned their hypothesis that scintigraphy could meet minimum scientific requirements as a diagnostic tool, Dyson said. In the end, it’s not a sure method for diagnosing lameness or poor performance—as it misses too many sources of pain and can also provide false positive results.
However, scintigraphy still has a place in lameness evaluations, she added. It can be very beneficial in certain situations, such as confirming a suspected bone-related injury in the foot.
“Scintigraphy is particularly useful for determining the likely clinical significance or otherwise of ossification of the ungular cartilages (sidebone),” Dyson said. “If sidebone was detected on radiographs, a targeted scintigraphic examination of the foot could be a cheaper and quicker option than MRI.”
Where it’s unlikely to be useful is for general screening when the reason for lameness or poor performance is unknown.
“What often happens in practice is that if a horse is not obviously lame, but is performing poorly, certain veterinarians tend to suggest scintigraphy as a screening tool,” Dyson said. Of course, if the scintigraphy turns up positive for pain in the foot, that could help identify the problem. But even then, that wouldn’t mean the problem is limited to just that scintigraphic finding.
It’s better to first use nerve blocks to try to find out what bodily region is responsible for the pain and get an expert lameness workup, she added.
“I see limited value in whole-body screening of sports and leisure horses, but targeted examinations can be useful in some clinical situations,” Dyson said. “And as with any other imaging modality, image quality and correct image interpretation are crucial.”
The study, “Evaluation of the diagnostic accuracy of skeletal scintigraphy for the causes of front foot pain determined by magnetic resonance imaging,” was published in Veterinary Radiology and Ultrasound.