Trigger point injection therapies for chronic myofascial neck and back pain: A systematic review.

[OBJECTIVE] To assess the comparative effectiveness and harms of trigger point injections (TPI) for myofascial neck and back pain.

[METHODS] Electronic literature databases were searched to identify articles pertaining to TPI for chronic myofascial neck and back pain. Searches were done from database start dates up to April 2020. Inclusion criteria were randomized controlled trials, cohorts, and case control studies. Pain, functional outcomes, and harms were extracted. Outcome time points were divided into short term (7 days to <6 weeks), intermediate term (6 weeks to ​< ​3 months), long term (3 months to ​< ​6 months), and longest term (>6 months). Quality assessment was done using the Cochrane Back Review Group (CBRG) checklist for RCTs, and the Newcastle-Ottawa Quality Assessment Scale for cohort and case control studies.

[RESULTS] 14 studies met inclusion criteria. Six studies compared TPI of Botulinum toxin A (five with Onabutulinum toxin A, and one with Abobotulinum toxin A) with normal saline (NS). Two of the Onabotulinum toxin A studies showed greater pain improvement in the Onabotulinum toxin A group at short, intermediate, compared with NS. The Abobotulinum study showed pain improvement at short, intermediate, and long terms. Of note Onabotulinum toxin A was associated with improved anxiety and depression in two studies. Two studies compared Onabotulinum toxin A to local anesthetic, one to methylprednisolone, and one to dry needling (DN), all of which showed no difference. One study compared Ozone to Lidocaine and DN, and it showed no difference. Two studies compared sterile water to NS; they both found no difference in pain outcomes at the short term time point. However one of these two studies showed improved pain at intermediate, long, and longest terms in the sterile water group. Tropisetron showed no difference vs. NS. Adverse effects were mostly reported for Onabotulinum toxin A and Abobotulinum toxin A.

[CONCLUSION] Given the mixed results, we are unable to conclude whether an injectate composition is superior to another, or make recommendations in that regard. Further studies will help elucidate the ideal injectate composition and parameters.