Comparison of lameness scores after a low 4‐point nerve block to lameness scores after additional desensitisation of the dorsal metatarsal nerves in horses with experimentally induced pain in the metatarsophalangeal joint

Abstract

Summary This study evaluated whether anaesthesia of the dorsal metatarsal nerves in addition to a low 4‐point nerve block provides significantly more analgesia to the metatarsophalangeal joint than to a low 4‐point nerve block alone. A wireless, inertial, sensor‐based, motion analysis system was used to evaluate gaits of six horses before induction of lameness, after administration of interleukin‐1β into a metatarsophalangeal joint, after anaesthesia of the medial and lateral plantar nerves and the medial and lateral plantar metatarsal nerves, and after additional anaesthesia of the lateral and medial dorsal metatarsal nerves. The magnitude of hindlimb lameness was analysed considering both the push‐off component (diffmaxpelvis) and the impact component (diffminpelvis) of the lame limb for all trials. There was no significant difference in the sum of diffmaxpelvis and diffminpelvis (SDMPs) when comparing the horse's gait after the low 4‐point nerve block to the gait after additional anaesthesia of the dorsal metatarsal nerves, indicating that there is likely no benefit of medial and lateral dorsal metatarsal nerve anaesthesia when using regional anaesthesia to localise pain to the metatarsophalangeal joint during a lameness examination.

Systematic approach to localisation of lameness in the distal limb of horses

“…Although the block can be performed with the limb lifted, I prefer to perform it with the limb weight bearing as the landmarks are easier to palpate and uptake of the block seems to be more reliable. Historically, in the hindlimb, it was deemed necessary to block the dorsal branches of the peroneal nerve abaxial to the long digital extensor tendon on the dorsal metatarsus (the low six‐point nerve block), but this is now deemed unnecessary to fully block the fetlock joint (Coleridge and others 2020).…”

Anatomical position of the palmar/plantar nerves at the metacarpal/metatarsal distal level in horses: An in vivo study by means of ultrasonography

“…The low six‐point block approach is used in the metatarsal distal third (Dyson & Kidd, 1993), as it also desensitizes the dorsal metatarsal nerves (Barker, 2016). However, the additional desensitization of these nerves does not seem to influence the lameness with origin in the fetlock joint (Coleridge et al, 2020). At these points, the nerves cannot be identified by palpation, or it is very difficult to do so.…”