The sacroiliac joints: evaluation using nuclear scintigraphy. Part 1: The normal horse.

This research focuses on enhancing diagnosis and understanding of sacroiliac (SI) disease in horses through scintigraphic imaging. It concludes that there is a substantial difference in radiopharmaceutical uptake between the fifth lumbar vertebra and the sacroiliac joints in normal horses; this varies with age but not gender, and demonstrates a high degree of bilateral symmetry.

Research Methodology

• The researchers selected 15 horses, extracted from a clinic database, for scintigraphic imaging. These images were then analyzed by two authors, comparing the output of both noncorrected images and motion-corrected images.
• To better understand the scintigraphic anatomy, images of 10 Thoroughbred horses were superimposed over a ventrodorsal radiographic image of an isolated pelvis.
• Subsequently, scintigraphic images of a cohort of 40 normal horses, aged between 3 and 16, were evaluated applying subjective examination, profile analysis, and quantification with regions of interest.

Research Findings and Interpretation

• The tubera sacrale, the rounded upper part of the sacrum, was identified as two defined oval areas on either side of the midline. The sacroiliac joints were represented by larger oval areas displaying less radiopharmaceutical uptake, suggesting lower disease levels.
• The researchers observed that, for younger horses, there was a clearer distinction between the sacroiliac region and the tubera sacrale. However, nonmotion-corrected images tended not to offer diagnostic data or could be misinterpreted as abnormal.
• Significant differences were noted in radiopharmaceutical uptake between the tubera sacrale and sacroiliac joints in comparison with the fifth lumbar vertebra. As the horses aged, there was a decrease in uptake in the tubera sacrale but no change in the sacroiliac joint region. There was also no noticeable effect of the gender of the horse on the radiopharmaceutical uptake.
• The study found a high level of symmetry in the left-right distribution of the tubera sacrale and sacroiliac joint regions.

Inferences and Implications

• The study suggests that for horses suspected of sacroiliac disease, their scintigraphic images should be contrasted with those of normal horses of a similar age. This helps establish relative norms and better identify potential abnormalities.
• In normal horses, high symmetry is observed between the left and right sacroiliac regions. Thus, significant left-to-right asymmetry may be an indicator of abnormal conditions, providing a clearer diagnostic criteria for sacroiliac disease in horses.