Influence of age and gender on quantitative sacroiliac joint scintigraphy

The value of quantitative sacroiliac joint scintigraphy for detecting sacroiliitis is controversial. Age and gender may contribute to this discordance. In previous reports, the number of control groups has been small and might not exactly reflect the change of sacroiliac/sacral (SI/S) ratios related to different age. In addition, the selection of control subjects was not strict. In most studies, care was not taken to ensure that control subjects did not have a history of back pain or any other relevant conditions. In addition, there was no requirement for a normal radiograph as a condition of inclusion. The aim of our study was to evaluate the consequent changes in SI/S ratios, according to age (in 10-yr intervals) and gender.

Over a period of 5 yr, 413 control subjects without a history of back pain, scoliosis, kyphosis, joint pain, arthritis, lesions within the pelvis, chemotherapy or systemic disease such as diabetes or systemic lupus erythematosus were included in this study. A posterior planar film of the pelvis was obtained to calculate SI/S ratio 3 hr after injection of 740 MBq 99mTc-methylenediphosphonate. Our data showed that: (a) the change in SI/S ratios related to age was significant in both females and males; (b) the SI/S ratios were higher in males younger than 30 yr and higher in men in the 41-50-yr age group and in females in other groups; (c) the SI/S ratios declined steadily with increasing age in females, whereas there were two plateaus in men aged 21-40 yr and 41-70 yr; (d) there were significant differences of SI/S ratios between the genders in certain age groups; and (e) no differences were found between left SI/S ratios and right SI/S ratios.

The influence of age and gender on SI/S ratios are substantial, and it is essential for each department to establish its own values for SI/S ratios based on gender and age (in 10-yr intervals).