Effect of Clostridium botulinum toxin type A injections into the deep digital flexor muscle on the range of motion of the metacarpus and carpus, and the force distribution underneath the hooves, of sound horses at the walk.

The research explores the use of Clostridium botulinum toxin type A injections into a horse’s deep digital flexor muscle as a potential treatment for laminitis, and reveals that it doesn’t substantially alter the animal’s gait.

Explanation of Research

• This study investigates the efficacy of using Clostridium botulinum toxin type A, commonly known as Botox, as a therapeutic treatment for laminitis in horses. Laminitis is a serious disease affecting the feet of horses leading to severe pain and lameness. The aim of the study was to see if the toxin could decrease muscle activity in the deep digital flexor muscle (DDFM), easing the pull on the distal phalanx (lowermost bone in the limb), potentially preventing displacement and alleviating pain.
• The researchers’ hypothesis was that if the toxin effectively reduced DDFM activity without negative side effects, it could then be used as a viable treatment for laminitis. Specifically, they were testing whether reduced DDFM activity would change the sagittal range of motion (vertical movement) of the metacarpus (part of the limb between the carpus or wrist and the phalanges or digits), the range of motion of the carpus (wrist), the distribution of force beneath the hooves, and the distribution of force between treated and untreated limbs.
• Consequently, they administered toxins into the left forelimbs of seven Royal Dutch Sport Horses while using ultrasound guidance and electromyography (measuring muscle response or electrical activity). The team took measurements with a pressure plate and inertial sensor system before and after the injections to carefully monitor any changes.
• The results showed that the sagittal range and carpal joint motions in the treated limbs notably increased after the injections, while it didn’t affect the balance or symmetry index. These indexes reflect the distribution of force under the hoof and between limbs respectively, and as such, suggest no change in the animals’ gait (the pattern of limb movement). Thus, no lameness was indicated as a side effect, supporting the hypothesis that Botox injection could be a potential therapeutic option to treat laminitis in horses without inducing substantial gait alterations at a walking pace.