The role of scintigraphy in the lameness evaluation

Bone scanning to help diagnose orthopedic disease has been used in human patients for over two decades. The value of this diagnostic tool has been well established in helping to identify a variety of musculoskeletal conditions. It has only recently been used by veterinarians for more accurate characterization of equine musculoskeletal disease. The technique offers the major advantage of increased sensitivity over standard radiographic imaging. The case material illustrated here shows that except for consistent identification of bone cysts, most of the pathologic changes to the horse's musculoskeletal system that might cause lameness are detected on bone scans. Many acute bone diseases can be diagnosed by scintigraphy that cannot be discerned by radiographs until the condition has become chronic: Because of their body size, these conditions may not be diagnosed at all in horses. Scintigraphy in horses offers the other major advantage of affording accurate imaging of the upper limbs, pelvis, and vertebral column without general anesthesia. Therefore, it has a final advantage of increased safety over conventional radiography because it eliminates the need to perform general anesthesia to study these areas. In the author's experience, if abnormal uptake of isotope in the upper limbs, pelvis or spine is not observed, general anesthesia to radiograph those areas is not warranted. A second major benefit of scintigraphic imaging is to differentiate mixed lameness conditions in which the component of bone disease must be separated from that of soft tissues to arrive at a rational course of treatment or prognosis. Finally, for athletic horses suspected of having lameness due to localized myositis, scintigraphy not only allows confirmation of muscle inflammation but also identifies the muscle bellies injured reasonably accurately so that specific local treatment may be given. Nuclear imaging of equine skeletal disease is an option that should be employed more frequently by equine practitioners for diagnosis of difficult lameness cases. The technique is safe and comparatively inexpensive when one considers the total expense of multiple examinations or radiographic surveys of patients without conclusively diagnosing the source or sources of skeletal pain. This is particularly true when a horse owner becomes dissatisfied and enlists the services of one or more other veterinarians. The equine specialist will maintain better client rapport if he or she suggests referral of the horse to a veterinary medical teaching center or private clinic where scintigraphic imaging can be done rather than having the client become frustrated and seek another opinion elsewhere.(ABSTRACT TRUNCATED AT 400 WORDS)