Quantitative scintigraphy of the sacroiliac joints.

The effects of age and laterality on sacroiliac (SI) to sacral indices and ratios were assessed in 62 patients. For the 14 controls, the left mean SI to sacral index was significantly higher than the right one. There was no correlation between age and SI to sacral ratio (= average of right and left index). The mean ratio in 36 patients with sacroiliitis and 12 patients with low back pain was not significantly different from that of the controls, with a clear overlap of indices between controls and sacroiliitis patients.