A comparison of the effects of two volumes of local analgesic solution in the distal interphalangeal joint of horses with lameness caused by solar toe or solar heel pain

The response of horses, with solar pain in the dorsal or palmar aspect of the foot, to 6 or 10 ml local analgesic solution administered into the distal interphalangeal (DIP) joint was examined. Lameness was induced in 7 horses by creating solar pain in the dorsal aspect of one forefoot and, at another time, the palmar aspect of the other forefoot with set-screws inserted into a custom-made shoe. Horses were videotaped trotting before and after application of set-screws and, in separate trials, after 6 or 10 ml local analgesic solution was administered into the DIP joint. Lameness scores were assigned by examining videotaped gaits. Scores were significantly lower (P < 0.05) for horses with set-screws applied to the angles of the sole and receiving 10 ml, but not 6 ml, local analgesic solution into the DIP joint. Scores were significantly lower (P < 0.05) for all horses with set-screws in the dorsal margin of the sole receiving either volume of local analgesic solution. Analgesia of the DIP joint was less effective in desensitising the angles of the sole than in desensitising the dorsal margin of the sole, and 10 ml local analgesic solution was more effective than 6 ml in desensitising these regions. The response of horses with solar pain to local analgesic solution in the DIP joint was influenced by the volume administered and the region of sole affected.