Intra-articular Botulinum Toxin A Targets Chronic Pain in Base-of-Thumb Osteoarthritis

The use of botulinum toxin A can be considered a fast-acting, intra-articular treatment that targets chronic pain in patients with base-of-thumb osteoarthritis (OA), according to study results published in The Lancet Rheumatology.

Hypothesizing that an intra-articular botulinum toxin A injection with splinting might have analgesic effects among patients with joint diseases, researchers sought to compare the effects of an injection of intra-articular botulinum toxin A with those of an injection of intra-articular saline in individuals with painful base-of-thumb OA.

The phase 3, double-blind, randomized controlled RHIBOT trial (ClinicalTrials.gov identifier: NCT03187626) was conducted at Cochin Hospital in Paris, France. Patients recruited for the study were adults who had evidence of trapeziometacarpal OA on x-ray, met the 1990 American College of Rheumatology criteria for OA of the hand, and reported a pain intensity score of at least 30 on an 11-point numerical pain rating scale (0=no pain, 100=maximal pain). Study patients were randomly assigned in a 1:1 ratio to 1 of 2 treatment groups: (1) the intervention group, who received an ultrasonography-guided injection of botulinum toxin A (50 Allergan units) in 1 mL of saline; or (2) the control group, who received an injection of 1 mL of saline alone.

Study recruitment was initiated on November 2, 2018, and follow-up was completed on April 23, 2021. Between November 2, 2018, and November 3, 2020, a total of 317 individuals were evaluated for eligibility, with 60 participants ultimately recruited — 30 to the intervention group and 30 to the control group. The mean participant age was 64.9±9.4 years. Overall, 78% of the participants were women and 22% were men.

At baseline, the base-of-thumb pain score was 60.0 of 100.0. The mean reduction in base-of-thumb pain at 3 months was -25.7 (95% CI, -35.5 to -15.8) in the intervention group vs -9.7 (95% CI, -17.1 to -2.2) in the control group (absolute difference, -16.0; 95% CI, -28.1 to -3.9; P =.043).

A total of 51 adverse events (AEs) were reported in both groups, with 27 AEs reported in the intervention group and 24 AEs reported in the control group. During follow-up, 14 individuals in the intervention group reported mild transient motor deficit of the thenar muscle compared with 2 individuals in the control group. There were no serious AEs reported.

No positive effects of intra-articular botulinum toxin A injection on pain were observed at 6 months because the biologic effects of botulinum toxin A only last up to 3 months.

Limitations of the study included the fact that the participants were recruited from a single center and the sample size was small, which may have been associated with larger estimates of treatment effect. Because ethnicity data were not collected as part of this study, any differential effects of the treatment according to race or ethnicity could not be estimated.

The study authors concluded, “Future studies are needed to investigate the potential mechanism of the effects observed in this trial, to replicate our findings, and to assess the effects of repeated injections over time and their clinical effectiveness, including an analysis of cost-effectiveness.”

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference  

Nguyen C, Abdoul H, Campagna R, et al. Intra-articular botulinum toxin A injection for painful base-of-thumb osteoarthritis: a double-blind, randomised, controlled, phase 3 trial (RHIBOT). Lancet Rheumatol. 2022;4(7):e480-e489. doi:10.1016/S2665-9913(22)00129-1