Trigger Point Injection for Myofascial Pain Syndrome of the Low Back: A Partially Blinded Three-Arm Randomized Controlled Trial

Abstract

Study objective: Low back pain is a common complaint in the emergency department (ED), often attributed to myofascial pain syndrome. Prior studies demonstrate trigger point injection efficacy in the ED in various body distributions, but only one has specifically assessed myofascial low back pain, and none have evaluated functional outcomes. The purpose of this study was to compare the efficacy of trigger point injections and standard therapy compared with standard therapy alone.

Methods: In this partially blinded, 3-arm randomized controlled trial, we randomized adults with low back pain and clinically identified trigger points to receive either standard therapy alone or a trigger point injection consisting of bupivacaine or normal saline solution with standard therapy. The primary outcome was change in pain at 30 to 60 minutes measured on a 10 cm visual analog scale. Secondary outcomes included changes in the Modified Oswestry Disability Index score at 30 to 60 minutes. Tertiary outcomes included change in pain on visual analog scale and Modified Oswestry Disability Index score at 60 to 72 hours compared with baseline.

Results: We randomized 180 participants (60 per cohort) into 3 arms. All treatment arms demonstrated pain reduction at 30 minutes. Compared with standard therapy alone, pain reduction at 30 to 60 minutes was 0.55 (95% confidence interval [CI] -0.19 to 1.28) for bupivacaine and 0.71 (95% CI 0.00 to 1.43) for normal saline solution. We found no difference among groups for pain or functional outcomes. No serious adverse events occurred.

Conclusion: We found no improvement with trigger point injections over standard therapy alone.

Keywords: Local anesthetic; Low back pain; Myofascial pain syndrome; Trigger point injection.