Botulinum toxin A injection may ease pain due to osteoarthritis of base-of-thumb: Lancet

France: The phase 3 RHIBOT trial found that Botulinum toxin A is effective in relieving pain and can be considered as a fast-acting, intra-articular therapy in individuals having osteoarthritis of base-of-thumb. The article was published in The Lancet Rheumatology.

Globally, millions of people suffer from Osteoarthritis, the most common form of arthritis. It occurs when flexible tissue at the ends of bones wears down. Osteoarthritis at the base of the thumb is a common and highly disabling condition that severely compromises the function of the entire hand. Botulinum toxins are neurotoxins that affect nerves. Botulinum toxin is a proven and widely used treatment for numerous conditions characterized by excessive muscular contractions. Recent studies have assessed the analgesic effect of botulinum toxin in joint pain. Intra-articular botulinum toxin A injection might have analgesic effects in patients with joint diseases.

Christelle Nguyen, Université Paris Cité, France and colleagues conducted a double-blind, randomised, controlled, phase 3 trial to compare the effects of intra-articular botulinum toxin A injection with those of intra-articular saline injection for patients with painful base-of-thumb osteoarthritis.

The research team recruited 60 adult patients with x-ray evidence of trapeziometacarpal osteoarthritis, who reported a pain intensity score of at least 30 on an 11-point numeric rating scale (0: no pain to 100: maximal pain). Participants were randomly assigned (1:1), to receive an ultrasound-guided injection of either botulinum toxin A (50 Allergan units) in 1 mL of saline (experimental group, n-30) or 1 mL of saline alone (control group,n-30) in the trapeziometacarpal joint, in addition to custom-made rigid splinting. The primary outcome was the mean change from baseline in base-of-thumb pain on a numeric rating scale at 3 months after injection, analysed by intention to treat.

Key findings of the study,

• Base-of-thumb pain score was 60•0 of 100•0, at baseline,

• At 3 months, the mean reduction in base-of-thumb pain was –25•7 in the experimental and control groups.

• Overall, 53% of the participants in the experimental group and 47% of participants in the control group reported adverse events.

• During follow-up, 47% of the participants in the experimental group and 7% of participants in the control group reported a mild transient motor deficit of the thenar muscle.

• No serious adverse events were reported.

The authors conclude that Botulinum toxin A could be considered a fast-acting, intra-articular therapy targeting chronic pain in individuals with base-of-thumb osteoarthritis. Future studies are needed to investigate the potential mechanism of the effects observed in this trial, to replicate the findings.

The effects of repeated injections of Botulinum toxin A in the long run and their clinical effectiveness, including an analysis of cost-effectiveness should be assessed, the authors wrote.

Reference:

Prof Christelle Nguyen, Hendy Abdoul, Raphaël Campagna, , Henri Guerini, , Léa Jilet, Catherine Bedin, et al. Published:July, 2022. DOI: https://doi.org/10.1016/S2665-9913(22)00129-1