Effects of analgesia of the digital flexor tendon sheath on pain originating in the sole, distal interphalangeal joint or navicular bursa of horses.

The research investigates whether pain relief of the digital flexor tendon sheath (DFTS) in horses also provides anaesthesia to other parts of the foot like the sole, distal interphalangeal joint (DIPJ), and navicular bursa (NB). The study finds that such analgesia has little impact on lameness caused by discomfort in these other foot areas.

Research Methodology and Design

• The research was conducted on 18 horses and designed to replicate foot pain via different trials. Lameness was artificially induced in different areas of the foot to evaluate how analgesia in the digital flexor tendon sheath might impact their discomfort.
• In Trial 1, pain was induced in the dorsal margin or heel region of the sole of the foot of five horses using set-screws to put pressure on the foot’s solar area, simulating the impact of pain originating from the sole.
• In Trial 2, an endotoxin was administered intrasynovially into the DIPJ in six different horses, replicating pain originating from the joint.
• Trial 3 followed a similar procedure as Trial 2, but the endotoxin was administered into the NB of seven horses, replicating pain in the NB.
• After induction of pain, the walking gait of each horse was evaluated using videotape footage, both before and after pain creation and after administration of mepivacaine hydrochloride into the DFTS. The lameness scores were then calculated and compared.

Research Findings and Conclusions

• In Trial 1, there was no notable difference in lameness scores at ten minutes post-injection, but significant improvement was observed at the twenty-minute mark post-injection.
• However, in Trials 2 and 3, there was no significant difference in lameness scores at both the ten and twenty-minute observations post-injection into the DFTS.
• The findings suggest that DFTS analgesia has a minimal impact on lameness caused by pain in the foot sole, DIPJ, or NB.
• The study concluded that any improvement in lameness after intrasynovial analgesia of the DFTS may be attributed to the attenuation of pain within the structures contained in the DFTS, and not due to an effect on other parts of the foot.