Today’s case takes you into the world of equine nuclear scintigraphy! For those of you that haven’t seen one before, we inject Technetium-99m-MDP, which is a radioisotope that localizes to active bone. After a few hours, we can take the images and find areas of increased uptake that can indicate inflammation, fracture, or neoplasia. The images will look grainy because they have low spatial resolution, but they are very sensitive to small changes in activity. This type of functional imaging can give us a lot of information about biological processes. Take a look!
The case is a 4 year old Thoroughbred filly in race training with intermittent right hind limb lameness for the last few months.
Radiographs of the tarsus and tibia are normal.
There is increased uptake of radioisotope on the right ilium, which indicates focal bone remodeling. The hind limbs are normal.
Stress fracture of the right ilium.
Common areas for stress fractures in racehorses include the tibia, humerus, scapula, metacarpus, and ilium. Oblique views of the pelvis, in addition to dorsal views, can help to isolate the lesion.
Hornof, W. J., S. M. Stover, P. D. Koblik and R. M. Arthur (1996). “Oblique views of the ilium and the scintigraphic appearance of stress fractures of the ilium.” Equine Veterinary Journal 28(5): 355-358.
Mackey, V. S., D. R. Trout, D. M. Meagher and W. J. Hornof (1987). “Stress fractures of the humerus, radius, and tibia in horses. Clinical features and radiographic and/or scintigraphic appearance.” Veterinary Radiology 28(1): 26-31.