The effect of regional nerve blocks on the lameness caused by collagenase induced tendonitis in the midmetacarpal region of the horse: a study using gait analysis, and ultrasonography to determine tendon healing.

This research article discusses the impact of regional nerve blocks on lameness in horses due to tendonitis in the midmetacarpal region, induced by collagenase injections. The effects were monitored over a period of 144 days using clinical examinations, ultrasonographic imaging, kinetic gait analysis, and post-mortem evaluations.

Regional Nerve Blocks and Lameness

• The study included six horses and the formation of tendonitis was facilitated in the midmetacarpal region of the Superficial Digital Flexor Tendon (SDF), Deep Digital Flexor Tendon (DDF), and the Suspensory Ligament (SL) through collagenase injections.
• These injections of collagenase mimic the injury process in horses, leading to tendonitis and lameness.

Monitoring Tendon Healing

• Sequential clinical examinations, ultrasonographic imaging, and kinetic gait analysis were utilized to monitor the effects of the induced tendonitis over a period of 144 days post-injection.
• Improvements and changes were noted and compared against gross and microscopic findings.

Results and Findings

• The research found that lameness resulting from SDF and DDF tendon lesions was completely eliminated through the use of high palmar nerve block.
• In the case of SL desmitis, it was only partially alleviated using a high palmar nerve block but was completely blocked when an additional ulnar nerve block was implemented.
• Ultrasonic evaluations showed that the lesions reformed until approximately 30 days post-injection, after which they began to decrease.
• The texture of the tendon lesion also showed marked improvement after 30 days.

Post-Mortem Evaluation

• A macro and microscopic post-mortem evaluation revealed that significant abnormalities remained present at 145 days post-injection.
• Despite this, ultrasonography was no longer able to detect the tendon lesions at this stage.

Conclusion

• The study was able to shed light on the effectiveness of regional nerve blocks in addressing lameness caused by collagenase-induced tendonitis in horses.
• It highlighted the variation in responses among the different tendons and ligaments, and the impact of additional nerve block applications.
• The research also raised questions on the strength and reliability of ultrasonography in identifying tendon lesions in the long term, as the lesions were no longer identifiable at 145 days, despite the presence of considerable abnormalities. This suggests potential limitations of ultrasonographic imaging in assessing the real status of tendon healing.