An Objective Assessment of the Effect of Desensitizing the Median Nerve on Lameness Originating from the Cubital Joint

 

Introduction: The median nerve is often desensitized along with the ulnar nerve when performing a lameness examination. Due to the close proximity of the median nerve to the cubital joint, proximal migration of local anesthesia is possible resulting in amelioration of a lameness originating from the cubital joint. The objective was to determine if performing a median nerve block will desensitize the cubital joint.

Materials and Methods: A forelimb lameness was induced in six healthy horses by injecting 100 ng of recombinant equine interleukin IL-1β into the cubital joint. The median nerve of the lame leg was anaesthetized using 10 mL of local anaesthetic solution. Successful block was confirmed by loss of skin sensation and thermographic images. Lameness was assessed at 20-, 40- and 60-minute intervals using the Lameness Locator. A full-factorial repeated measures ANOVA was used to compare treatment effect across time.

Results: IL-1β administration resulted in significant transient lameness in all horses (p < 0.00001). The median nerve block was successfully performed in all horses and did not result in significant improvement of lameness as quantified by the total differential head vector sum (p = 0.3234).

Discussion/Conclusion: Complete desensitization of the median nerve did not ameliorate lameness originating from the cubital joint. This result has relevant clinical application as it suggests, when performing a lameness examination, it is unlikely that blocking the median nerve with a low volume of local anaesthetic will block a lameness originating from the cubital joint.

Acknowledgement: There was no proprietary interest or funding provided for this project.