Double-blind, Prospective Comparison of Medications Used in Trigger Point Injections - Ketorolac, Lidocaine, or Dexamethasone

Background

Trigger point injections (TPIs) are a commonly-performed procedures by physicians for the treatment of myofascial pain, specifically targeting myofascial trigger points (MTrPs). Commonly injected substances include local anesthetic, botulinum toxin, or corticosteroid (CS), though non-steroidal anti-inflammatory drugs (NSAIDs) and other substances have been reported. A Cochrane review found that intramuscular injection of local anesthetic demonstrated moderate evidence of benefit for mechanical neck disorders; no other treatment demonstrated greater benefit.

Great variation is seen in how TPIs are performed, however. The standard method was described by Simons and Travell, and is often cited. Hong et al. demonstrated that, similar to the technique described by Simons and Travell, obtaining a local twitch response (LTR) was the most important factor in producing pain relief. Further research by Shah et al., which demonstrated an inflammatory component to MTrPs, also showed a decrease in inflammatory cytokines following trigger point injections that obtained a LTR. Despite these findings, most studies do not use the LTR method in their TPI techniques.

Prior studies demonstrated that most patients obtain significant relief from TPI, but did not identify differences between injection of CS or other substances. However, none of these studies identified LTRs in their injection techniques.

As can be learned from a review of the published literature on muscular trigger points, the cause of this condition is unknown, and no single treatment approach has been established as a clearly accepted gold standard treatment. There is evidence, however, that there is an inflammatory component associated with trigger points and that obtaining a local twitch response is associated with a decrease in local inflammation at the site of a trigger point. The combination of injecting an anti-inflammatory medication and obtaining a local twitch response has never been studied. The purpose of this study is to examine the comparative effectiveness of injectable substances on patient outcome after a TPI with LTR identified, namely a CS (dexamethasone), a NSAID (ketorolac), or only a local anesthetic (lidocaine).