Intra‐articular anaesthesia of the equine stifle improves foot lameness

Abstract

Summary Background Equine diagnostic anaesthesia can be a useful tool in challenging lameness examinations. However, anaesthetics diffuse over time leading to nonspecific desensitisation of periarticular structures. Nerves that convey sensation from the distal limb to the central nervous system pass in close proximity to the caudal stifle joint capsule. Therefore, diffusion of intra‐articular (IA) anaesthetics could cause inadvertent desensitisation of the distal limb resulting in a false diagnosis of stifle lameness. Objectives To determine if IA stifle anaesthesia can alleviate lameness originating in the distal limb. Study design Crossover experiment. Methods Nine horses were fitted with a circumferential hoof clamp to induce a moderate unilateral hindlimb lameness. Intra‐articular stifle anaesthesia was performed and gait was evaluated every 10 min during the 90‐min trial using an inertial sensor system. Push‐off and landing components of the lameness were assessed by measuring the mean inter‐stride difference between the maximum and minimum heights of the pelvis respectively. Differences were compared using a Wilcoxon signed‐rank test. Results Overall, horses with hoof clamp‐induced foot pain had a reduction in push‐off lameness after IA stifle anaesthesia. The mean change in diffmax at 90 min was −4.3 mm (P = 0.005) for the experimental group vs. −2.3 mm (P = 0.2) for the control group. Lameness decreased over time, with an average improvement of 23% at 30 min, 33% at 60 min and 38% at 90 min. There was high inter‐horse variability; 3/9 horses improved by ~50% within 30 min, while 2/9 improved by ~30% and 4/9 had minimal (<10%) or no improvement in lameness. Improvement after IA stifle anaesthesia was not related to the severity of baseline lameness (P = 0.3–0.7). Main limitations Limited clinical applicability of our lameness induction model. Conclusions Intra‐articular stifle anaesthesia reduces foot lameness in a third of horses by up to 50% within 30 min. Clinically, the results of IA stifle anaesthesia should be considered in the light of these findings before treatment recommendations are made, as additional diagnostics may be required to rule out pain originating in the distal limb.

Equine bone cysts: What do we know about them and their treatment?

“…It has been recently reported that foot‐induced lameness can improve up to 50% in a third of horses after anaesthetising the stifle compartments (Radtke et al . 2020), which could be compatible with the amelioration in lameness seen in this case. In addition, the lack of obvious radiographic or arthroscopic communication between the joint and the cyst could prevent an intuitive explanation for the lameness improvement seen.…”

Desensitisation of the distal forelimb following intrathecal anaesthesia of the carpal sheath in horses

“…Jordana et al 13 reported complete heel bulb desensitisation after injecting the digital flexor tendon sheath in 31% of the limbs investigated between 30 and 120 minutes. In addition, intra‐articular anaesthesia of the stifle joint compartments produced up to 50% improvement in 3/9 horses with foot‐induced lameness by 30 minutes 14 . Our study demonstrates that intrathecal anaesthesia of the carpal sheath with 2% mepivacaine hydrochloride can induce inadvertent distal limb desensitisation.…”

An investigation into the association between plantar distal phalanx angle and hindlimb lameness in a UK population of horses

“…Due to the predominance of stifle lameness in this study, it is important to acknowledge a recent study that suggested intra‐articular anaesthesia of the stifle could inadvertently desensitise the distal limb (Radtke et al . ). Radtke et al .…”

“…Radtke et al . () stated that intra‐articular stifle anaesthesia can reduce foot lameness in a third of horses by up to 50% within 30 min, but there was high inter‐horse variability. As a low four‐point nerve block was performed prior to intra‐articular anaesthesia of the stifle, diffusion of local anaesthetics from the stifle joint did not desensitise the distal limb and result in misinterpretation of lameness localisation in our study.…”