Are paraspinous intramuscular injections of botulinum toxin a (BoNT-A) efficient in the treatment of chronic low-back pain? A randomised, double-blinded crossover trial.

[BACKGROUND] Treatment for patients with chronic low-back pain (LBP) is a public health issue. Intramuscular injections of botulinum toxin A (BoNT-A) have shown an analgesic effect on LBP in two previous randomized controlled studies. The objective of the study was to verify the efficacy of paravertebral injections of BoNT-A in patients with LBP.

[METHODS] Patients were included in this phase 3 randomized double-blinded trial comparing the efficacy of BoNT-A versus placebo in a crossover study on LBP. Both groups received 200 units of BoNT-A in paravertebral muscles or a placebo, and vice versa at Day 120. The main judgment criterion was LBP intensity 1 month after the injections, evaluated by using a visual pain scale (VAS). Secondary assessment criteria included: LBP intensity 90 and 120 days after injection day; number of days when an allowed antalgic oral treatment was needed in between each evaluation; functional disability measured by the Quebec Back Pain Disability Scale; quality of life; inability to work; patient satisfaction in relation to the treatment's effect; spinal mobility; and strength of spinal muscles, measured by isokinetic technique.

[RESULTS] Nineteen patients completed the study. There was no significant difference between the groups' average LBP during the last 8 days at Day30 (p = 0.97). There was no significant difference between the two groups regarding the secondary assessment criteria (p > 0.05).

[CONCLUSIONS] Injections of BoNT-A in the paravertebral muscles were not found to be effective to relieve chronic LBP. The limits of the study are that the dose of BoNT-A used was lower than in other studies, and that the limited number of patients included may explain the negative results.

[TRIAL REGISTRATIONS] Identifiers: NCT03181802 . Unique Protocol ID: CHUBX2003.