Intensity mapping of pain referral areas in sacroiliac joint pain patients.

OBJECTIVE: To identify differences in pain referral areas, using intensity maps, between responders and nonresponders to a double diagnostic sacroiliac joint injection with a short- and long-acting local anesthetic in patients with chronic low back pain.
METHODS: From a group of 140 consecutive patients with chronic low back pain, 60 patients who met clinical criteria were included in the study. Twenty-seven demonstrated a positive response to a double diagnostic fluoroscopically guided intra-articular sacroiliac joint block and were compared with 33 patients with a negative response. Each patient's preinjection pain diagram was used to determine areas of pain referral. The summation of these pain referral zones for both groups was used to construct intensity maps.
RESULTS: No major differences were observed between responders and nonresponders with regard to mean size and distribution of referral pain areas. Intensity maps, however, showed differences in pain referral at the buttock in the areas overlying the sacroiliac joint (100% of the responders vs 80% of the nonresponders) and the ischial tuberosity (10% of the responders vs 100% of the nonresponders).
CONCLUSIONS: Overall referred pain maps appeared not to be useful to discriminate patients with an identified sacroiliac joint pain from chronic low back pain patients with pain from other sources. Differences were only found using intensity maps. By implementing these data, it could be concluded that patients with sacroiliac joint pain are less likely to experience pain in both the 'Fortin' and 'tuber' areas. This knowledge can be used as additional selection criterion for putative sacroiliac joint patients, next to sacroiliac joint pain provocation tests.