RESUMO
OBJECTIVE: To describe pathological findings identified with MRI in the distal tarsal bones of horses with unilateral hind limb lameness attributable to tarsal pain and to compare the usefulness of MRI with that of radiography and nuclear scintigraphy in evaluation of this region. DESIGN: Retrospective case series. ANIMALS: 20 lame horses. PROCEDURES: In all horses, MRI, radiography (4 standard projections), and nuclear scintigraphy of the tarsus had been performed. Horses were excluded if the results of all 3 imaging modalities were not available or if lameness was detected in more than 1 limb. Pathological changes identified with MRI were cross-referenced with the findings determined with other imaging modalities. RESULTS: Compared with MRI findings, the following lesions were identified with radiography: medullary and subchondral bone sclerosis in 9 of 16 horses, pathological changes related to osseous hyperintensity in 0 of 10 horses, and osteoarthritis in 5 of 8 horses. Standard radiographic projections did not aid in the identification of fracture of the distal tarsal bones (3 horses). Location of increased radiopharmaceutical uptake with nuclear scintigraphy corresponded with the location of pathological changes detected with MRI in all horses. The intensity of the radiopharmaceutical uptake on nuclear scintigraphic images did not correspond with the severity of the pathological changes identified with MRI. CONCLUSIONS AND CLINICAL RELEVANCE: Radiography was unreliable for the detection of pathological changes related to osseous hyperintensity identified with MRI, fracture, and subchondral bone sclerosis in the equine tarsus. Nuclear scintigraphy was effective in localizing pathological changes, but MRI provided superior anatomic detail.