Does immediate pain relief after an injection into the sacroiliac joint with anesthetic and corticosteroid predict subsequent pain relief?

Abstract

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%, -2.6, 95% CI=1.1-5.9) demonstrated 50% or greater pain relief at follow-up, and four of 11 (36.5%, 95% CI28.4%, -3.00, 95% CI=1.4-5.1) had 100% relief at two to four weeks. Fourteen of 14 (100%, 95% CI21.5%, -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.