TriggerPointInjectionforMyofascialPainSyndromeoftheLowBack:APartiallyBlindedThree-ArmRandomizedControlledTrial

Low back pain is one of the most common reasons people visit emergency departments, accounting for 4.4% of worldwide ED presentations and costing approximately $100 billion per year in the United States. While most mechanical low back pain improves within six weeks, a subset of patients have pain caused by myofascial pain syndrome — a condition characterized by hyperirritable trigger points in muscle that cause regional, non-dermatomal referred pain. Emergency physicians have increasingly used trigger point injections as a non-opioid treatment option, with prior studies suggesting they could provide rapid pain relief. However, most prior research was conducted in physical therapy or rehabilitation settings rather than emergency departments, and no ED study had specifically evaluated functional outcomes after discharge.

The investigators aimed to determine whether adding trigger point injections to standard emergency department care would improve pain and function for patients with myofascial low back pain.

The researchers conducted a partially blinded, three-arm randomized controlled trial at a single academic military hospital emergency department with 60,000 annual visits. They enrolled 180 adult patients presenting with low back pain and clinically identified trigger points between January 2021 and February 2024. Participants were randomized in permuted blocks of nine to one of three groups: standard therapy alone (intramuscular ketorolac 30 mg plus oral acetaminophen 975 mg in the ED, with ibuprofen, acetaminophen, cyclobenzaprine, heat therapy, and McKenzie exercises at discharge); standard therapy plus trigger point injection with 0.5% bupivacaine; or standard therapy plus trigger point injection with normal saline solution. The trigger point injection arms were double-blinded to both participants and providers, though the standard therapy alone arm could not be blinded for ethical reasons.

Pharmacists prepared indistinguishable injectates in prefilled syringes. Investigators administered up to four trigger point injections of 2 mL each. The primary outcome was change in pain at 30 to 60 minutes measured on a 10 cm visual analog scale. Secondary outcomes included change in the Modified Oswestry Disability Index at 30 to 60 minutes.

Tertiary outcomes assessed pain and function at 60 to 72 hours via telephone follow-up. The study was designed to detect a clinically meaningful difference of 1.5 cm on the VAS with 80% power.

All three treatment groups demonstrated pain reduction at 30 minutes, but there were no significant differences between groups. Compared with standard therapy alone, pain reduction at 30 to 60 minutes was 0.55 cm (95% confidence interval -0.19 to 1.28) for bupivacaine and 0.71 cm (95% CI 0.00 to 1.43) for normal saline solution — neither meeting the predetermined threshold for superiority of 1.5 cm. At 60 to 72 hours, the differences were 0.45 cm (95% CI -1.11 to 0.20) for bupivacaine and 0.09 cm (95% CI -0.79 to 0.62) for normal saline compared with standard therapy alone. Functional outcomes measured by the Modified Oswestry Disability Index similarly showed improvement in all groups without significant differences between groups.

At 30 to 60 minutes, the difference in functional improvement compared with standard therapy alone was 9.44 (95% CI 3.93 to 14.96) for bupivacaine and 5.18 (95% CI -0.08 to 10.45) for normal saline. Notably, the bupivacaine arm had more side effects including bleeding from injection (5.7%) and soreness (11%), though no serious adverse events occurred and none required further treatment. The trigger point injection arms required less additional rescue pain medication than standard therapy alone. Compliance with discharge medications, stretching, and heat therapy was highest in the standard therapy alone group.

Blinding was imperfect: 21% of participants and 26% of investigators correctly guessed their treatment assignment.

This study challenges the assumption that trigger point injections add meaningful benefit for myofascial low back pain in emergency department patients who can receive standard multimodal therapy. The findings suggest that standard care with NSAIDs, acetaminophen, muscle relaxants, and self-directed exercises may be sufficient, and that the additional invasive procedure of trigger point injection may not be warranted for most patients. The equivalence between bupivacaine and normal saline injectates, while not conclusively demonstrated due to potential ceiling effects, is consistent with prior research suggesting that the mechanical effect of needle insertion may be as important as any pharmacologic effect. For clinicians, this means considering whether resources and time spent on trigger point injections could be better allocated, particularly in busy emergency departments.

For patients, the message is reassuring: standard non-opioid medications and simple home measures like heat and stretching appear to work just as well as injections. However, the study was conducted in a predominantly young, male military population, so results may not generalize to all ED patients. Additionally, the study could not address whether certain subgroups — such as those unable to take oral medications or with specific trigger point characteristics — might still benefit from injections. Future research should explore whether trigger point injections have a role when standard therapy is contraindicated or in patients with refractory chronic pain.