An Objective Assessment of the Effect of Anesthetizing the Median Nerve on Lameness Caused by Pain in the Cubital Joint.

The research study explores whether anesthetizing the median nerve in horses can help mitigate lameness caused by pain in the cubital joint. The study found that the median nerve block was not effective at improving induced lameness in horses, and thus it is suggested that using a 10 mL local anesthetic to block the median nerve is unlikely to help with pain originating from the cubital joint.

Research Methodology

• The research involved conducting a lameness examination on six healthy horses. Lameness was induced by injecting 100 ng of recombinant equine interleukin 1 beta (IL-1β) into the cubital joint of the animals. This substance is known to cause transient lameness in horses.
• The median nerve of the lame leg was then anesthetized with 10 mL of 2% mepivacaine hydrochloride. A successful median nerve block was confirmed through loss of skin sensation at the medial aspect of the pastern, as well as typical changes in thermographic images.
• The gait of the horses was assessed at various intervals—before, and at 20, 40, and 60 minutes after the median nerve block—using the Lameness Locator, an inertial sensor-based motion analysis system.
• The treatment effect across time was statistically analyzed using a full-factorial repeated measures analysis of variance.

Research Findings

• Injection of IL-1β into the cubital joint of the horses resulted in significant transient lameness in all of them, validating the method used for inducing lameness.
• The median nerve block was successfully performed on all the horses. However, it did not result in significant improvement of lameness as quantified by the total differential head vector sum, a measure of head nod severity.

Implications of the Study

• The study’s findings are relevant to both horse caretakers and veterinary professionals. It suggests that blocking the median nerve with 10 mL of local anesthetic during a lameness examination is unlikely to mitigate pain originating from the cubital joint.
• The research findings contribute to a better understanding of equine lameness examinations and suggest potential limitations of relying on median nerve anesthetic in managing pain in the cubital joint.