Nuclear scintigraphy is a diagnostic procedure that allows our veterinarians to diagnose difficult lameness cases. A very small amount of a radioactive substance is injected into the patient’s vein. The circulatory system carries this substance throughout the patient’s body and it localizes wherever there is increased bone turnover, or where there is increased blood supply to soft tissues. A device called a “Gamma Camera” is positioned over the horse’s body to detect where the radiation has localized. Once an area of concern is identified with scintigraphy, the problem can be further defined with radiographs, ultrasonography, or nerve and joint blocks, if needed.
Scintigraphy has several advantages over traditional diagnostics in some difficult cases, including: 1) It is a much more sensitive indicator of bone damage than radiographs; 2) The Gamma Camera can be positioned anywhere on the horse’s body, so we can image the back, head, or any other location needed. Clear radiographs of the back and pelvic regions are difficult to obtain in adult horses, so this is a huge advantage in diagnosing lameness; 3) Some areas of the horse can not be blocked in a traditional lameness examination; 4) With scintigraphy, very subtle causes of lameness can be detected. In a traditional lameness evaluation, a diagnosis is dependant upon the horse being visibly lame; and 5) Scintigraphy shows the blood flow to the distal limb, which can help in some injuries to tell when the blood supply has been lost.
Scintigraphy has several disadvantages, as well, when compared to regular diagnostics: 1) Radiation regulations require that the patient be hospitalized for 24 hours after the radioactive material is injected; and 2) In about 30% of chronic lameness cases, scintigraphy does not give a clear indication of the cause of lameness.