Local distribution of mepivacaine after distal interphalangeal joint injection in horses.

The research investigated the distribution of mepivacaine, a local anesthetic, after joint injection in horses. Findings suggest that mepivacaine hydrochloride deposited into the distal interphalangeal (DIP) joint may numb pain from the navicular bursa synovia and potentially reduce pain from the navicular bone’s medullary cavity.

Research Methodology

• The study was carried out with 10 adult horses. It was a prospective and uncontrolled study aimed at examining how the local anesthetic, mepivacaine, behaves after being injected into the dorsal pouch of a forelimb DIP joint.
• A quantity of 8 ml of 2% mepivacaine hydrochloride was injected into the joint 30 minutes before euthanasia.
• Upon euthanasia, tissue samples were acquired from the DIP joint and the navicular bursa and bone tissues were also taken from the medullary cavity of the navicular bone in both forelimbs.
• High-performance liquid chromatography was used to analyze all these tissue samples in order to determine the concentration of mepivacaine. This was done for the synovial and bone specimen concentrations in both the injected and noninjected forelimbs.

Research Findings

• Results showed that mepivacaine concentrations in the injected forelimb were significantly higher than in the non-injected limb.
• All synovial samples from the DIP joint and navicular bursa of the injected limb had mepivacaine concentrations greater than the estimated effective concentration needed for local anesthesia. This implies that the mepivacaine was successful in anesthetizing these regions.
• Among the 10 navicular bone samples from the injected limb, four exceeded and two were within 20% of the estimated effective tissue concentration needed for mepivacaine’s anesthetic effectiveness.

Conclusion

• These findings suggest that injecting mepivacaine hydrochloride into the DIP joint would numb pain originating from navicular bursa synovia. Moreover, pain from the medullary cavity of the navicular bone may also be reduced.
• The study also inferred that DIP joint injection of mepivacaine hydrochloride is not specific for DIP joint pain alone, as the anesthetic appears to spread to surrounding tissues to alleviate pain in those areas as well.