Relationship between scintigraphic and radiographic evaluations of spinous processes in the thoracolumbar spine in riding horses without clinical signs of back problems

Reasons for performing study: Radiography and scintigraphy are used to aid diagnosis of the cause of back pain, but a large variation in appearance and radiopharmaceutical uptake in fully functioning horses make diagnosis difficult. Objectives: To describe the range of and compare scintigraphic and radiographic findings in the spinous processes of horses without clinical signs of back problems. Methods: Thirty-three apparently normal riding horses underwent scintigraphic and radiographic examinations of the spinous processes in the thoracolumbar spine. Scintigraphic images were evaluated in a continuous blue, green and red colour scale, and the level of radiopharmaceutical uptake in the spinous processes from T10-L2 was graded into none, mild, moderate or severe increased radiopharmaceutical uptake. Structural changes along the borders of the spinous processes and the width of the interspinous spaces from T10-L2 were recorded. Results: Only 7 horses had no scintigraphic or radiographic findings. Nine horses had no increased radiopharmaceutical uptake, 17 had no sclerosis, 21 had no radiolucencies and 11 had normal spacing of the spinous processes (>4 mm wide). The majority of findings in 26 horses were located from T13-18 and were mild. Conclusions: The findings of a wide spectrum of scintigraphic and radiographic changes leads to the conclusion that changes within this range found in affected horses cannot be interpreted as clinically significant. Potential relevance: To determine whether scintigraphy and/or radiography can be used to separate horses with back pain from horses without clinical signs, the results from this study should be compared to the scintigraphic and radiographic findings in horses with clinical signs.