Improvement in horses after intra-articular injection of botulinum neurotoxin

Lameness improvement in horses with distal tarsal pain after intra-articular injection of botulinum neurotoxin type A

Am J Vet Res. 2025 May 13:1-7. doi: 10.2460/ajvr.24.10.0294. Online ahead of print.
Authors
Antônio A Beck 1 2 , Letícia B Paz 1 , Maria I Frank 1 , Roberta C F Pereira 3 , Flávio D De La Côrte 3
Affiliations

1 Equine Veterinary Teaching Hospital, College of Veterinary Medicine, Federal University of Santa Maria, Santa Maria, RS, Brazil.
2 Marion duPont Equine Medical Center, Virginia-Maryland College of Veterinary Medicine, Leesburg, VA.
3 Department of Large Animal Clinics, College of Veterinary Medicine, Federal University of Santa Maria, Santa Maria, RS, Brazil.

PMID: 40359997
DOI: 10.2460/ajvr.24.10.0294

Abstract

Objective: To evaluate the effect of IA injections of botulinum toxin type A (BoNT-A) in horses with chronic, naturally occurring distal tarsal osteoarthritis.

Methods: 9 horses were selected after physical and radiographic assessments. Horses also underwent an objective lameness examination and were included if they had a hindlimb impact lameness (Pmin ≥ 3 mm), which positively responded (≥ 50%) to the tarsometatarsal and centrodistal joints’ anesthetic block. Horses randomly received an intra-articular injection of BoNT-A or an equivalent volume of saline solution. Horses were reevaluated at postinjection days (PIDs) 1, 7, 15, 30, 60, 90, 120, 150, and 180. Success criteria included a decrease in Pmin (≤ 3 mm) or an abolishment of lameness on the baseline lame limb with lameness shifting to the contralateral limb. A percentage of lameness improvement was calculated for all horses at all timepoints.

Results: 5 horses were included in the BoNT-A group, whereas 4 individuals were allocated in the placebo group. A significant improvement (P < .05) was observed in horses from the BoNT-A group when compared to placebo at PIDs 90, 120, 150, and 180. Two of 5 horses (40%) from the BoNT-A group had an absolute improvement (100%) in lameness at all the timepoints. Higher percentages of lameness improvement were observed at PID 60. Conclusions: The results of this study suggest that the intra-articular injection with 50 U of BoNT-A was effective in reducing lameness in horses with distal tarsal osteoarthritis, mainly 90 days after injection. Clinical relevance: Botulinum toxin type A can be considered as an option for managing horses with chronic osteoarthritis. Keywords: horse; intra-articular therapy; joint pain; osteoarthritis; toxin.