Most frequently, one of the causal lesions is present and the transition from the initial lesion to the joint infection is readily apparent. However, when a swollen foot is treated before the cause has been established, a joint infection may have been ongoing for weeks before the true nature of the condition is diagnosed. If aggressive treatment of a footrot case does not lead toward resolution within 3 days, septic arthritis should be suspected. Increased pain, together with swelling of the anterior region of the coronary band in cases of sandcrack and white line disease, is suggestive of joint infection. Using regional analgesia and strict aseptic technique, an aspirate of the joint can be collected and examined for infection. A radiograph may indicate an abnormal separation of the joint surfaces.
Infection enters the distal interphalangeal joint via three possible main sites: 1) the dorsal commissure of the interdigital space, via penetrating trauma or complicated footrot (interdigital phlegmon); 2) sandcracks; or 3) white line disease or retroarticular abscess.
Digital amputation is indicated in animals that have a limited life expectancy, eg, old or poor-producing animals. The procedure is simple, quick, can be performed in standing animals under regional analgesia, and in most cases, produces rapid relief. Amputation is performed through the skin with an embryotomy wire placed as close to the skin-horn junction as possible. Hemorrhage is arrested by means of a tight bandage.
Alternatively, in the case of valuable animals, arthrodesis to fuse the distal and middle phalanges may be attempted. General anesthesia is recommended. A 1-cm canal is drilled through the abaxial wall into the joint, and a second canal is drilled from the causal lesion into the joint. The joint cavity is enlarged by curettage, and a drainage tube drawn through. Continuous irrigation with sterile saline should be performed for 2–3 days. A wooden block is then applied to the sound claw and the affected digit immobilized by fixing it to the block with methyl methacrylate. Immobilization is further facilitated by encasing the digital region in a cast. The cast is removed after 4 wk.