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

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Abstract
The influence of regional nerve blocks on lameness resulting from tendon injury was studied in six horses. Tendonitis was induced in the midmetacarpal region of the Superficial Digital Flexor Tendon (SDF), Deep Digital Flexor Tendon (DDF) and the Suspensory Ligament (SL) through collagenase injections. The results were evaluated through sequential clinical examinations, ultrasonographic imaging and kinetic gait analysis (force plate) during a period of 144 days post injury and subsequently compared with gross and microscopic findings. The lameness corresponding to the SDF and DDF tendon lesions was completely abolished by a high palmar nerve block. The SL desmitis was partly abolished by high palmar nerve block and completely blocked with an additional ulnar nerve block. The ultrasonic evaluations showed the lesions, expanding until approximately 30 days post injection (p.i.) and subsequently decreasing. The texture of the lesion also improved markedly after 30 days p.i. The post-mortem macro- and microscopic evaluation revealed still considerable abnormalities at 145 days p.i. At that time the tendon lesions were no longer detectable ultrasonographically.