Does Immediate Pain Relief After an Injection into the Sacroiliac Joint with Anesthetic and Corticosteroid Predict Subsequent Pain Relief?

Objectives: To determine if immediate pain response following an injection with local anesthetic and corticosteroid predicts subsequent relief.

Design: Prospective observational cohort.

Setting: An institutional review board-approved prospective study from a single academic medical center.

Methods: Patients with clinical diagnosis of sacroiliac (SIJ) pain and referred for SIJ injection were enrolled; 1 cc of 2% lidocaine and 1 cc of triamcinolone 40 mg/mL were injected into the SIJ. Pain score on 0-10 numeric rating scale (NRS) during provocation maneuvers was recorded immediately before injection, immediately after injection, and at two and four weeks of follow-up. Oswestry Disability Index (ODI) was also recorded.

Results: Various cutoffs were identified to establish positive anesthetic response and successful outcomes at follow-up. These were used to calculated likelihood ratios. Of those with 100% anesthetic response, six of 11 (54.5%, 95% confidence interval [CI]+/-29.4%, +LR 2.6, 95% CI = 1.1-5.9) demonstrated 50% or greater pain relief at follow-up, and four of 11 (36.5%, 95% CI+/-28.4%, +LR 3.00, 95% CI = 1.4-5.1) had 100% relief at two to four weeks. Fourteen of 14 (100%, 95% CI+/-21.5%, -LR 0.0, 95% CI = 0.0-2.1) with an initial negative block failed to achieve 100% relief at follow-up.

Conclusions: Patients who fail to achieve initial relief after SIJ injection with anesthetic and steroid are very unlikely to achieve significant pain relief at follow-up; negative likelihood ratios (LR) in this study, based on how success is defined, range between 0 and 0.9. Clinically significant positive likelihood ratios of anesthetic response to SIJ injection are more limited and less robust, but are valuable in predicting 50% relief or 100% relief at two to four weeks.