Effects of analgesia of the distal interphalangeal joint or palmar digital nerves on lameness caused by solar pain in horses.

Abstract

To determine if pain of the dorsal margin of the sole in horses can be attenuated by anesthesia of either the distal interphalangeal (DIP) joint or the palmar digital (PD) nerves. A unilateral forelimb lameness was induced by creating solar pain. Response to administration of local anesthetic or saline solution into the DIP joint and to administration of local anesthetic around the PD nerves was evaluated. Six horses. Lameness was induced by creating pressure on the dorsal margin of the sole by screwing set-screws into a nut welded to the inside of each branch of a shoe. Gaits were evaluated before and after application of set-screws and after a local anesthetic or saline solution was administered into the DIP joint and, in a second trial, after a local anesthetic was injected around the PD nerves. Gaits recorded on videotape were evaluated, and lameness scores were assigned to each gait. Lameness scores were high after application of set-screws and remained high after saline solution was administered into the DIP joint. Scores decreased significantly (P < or = .05) after a local anesthetic was administered into the DIP joint or around the PD nerves. Analgesia of the DIP joint or the PD nerves desensitizes at least a portion of the sole. Pain arising from the sole should not be excluded as a cause of lameness when lameness is attenuated by analgesia of the DIP joint or PD nerves.