Surgery of the diseased bovine digit (Proceedings)
Deep sepsis of the digit
Untreated or late-treated foot rot, a complicated sole ulcer, a white line abscess that extends into retroarticular structures, and puncture wounds may all result in necrosis and or infection of structures important for weight bearing. These problems have in common severe pain that is not relieved by hoof blocks or analgesic medication. Specific diagnosis of the problem may be aided by using a probe to explore fistulous tracts, by inserting a hypodermic needle (14 or 16 g) into joints or tendon sheaths, but rarely requires X-radiography. Cows suffering from deep sepsis are truly suffering and a decision should be made at the first recognition of this problem to either euthanize, slaughter, or perform surgery. Too many cases receive no treatment or systemic antibiotics in the hope that the problem will somehow resolve spontaneously. These cows deserve a more humane approach.
Surgery of the digitAnesthesia is most easily performed by intravenous infiltration of lidocaine distal to a tourniquet on the metatarsus or metacarpus. Lidocaine without epinephrine, 20 to 30 ml, is infused using a butterfly catheter (19 g, 15 to 25 cm). Any accessible vein will result in complete anesthesia of both digits after a few minutes. If no vein can be found, regional perfusion above the intended surgical site is an alternative. The distal limb is scrubbed and disinfected as for any surgery but usually not shaven as the hair is typically very short or absent. Surgical procedures are commonly done in the field and are considered "clean" procedures but not sterile. The goal is to debride necrotic tissues and provide drainage for pus and exudate. If a hoof block is to be used as part of the therapy it should be attached before the surgery since adhesives require dry hoof to bond. Injecting the lidocaine followed by applying the block or scrubbing the area insures adequate time for diffusion of the anesthetic to all tissues distal to the tourniquet.
Toe ulcer, toe necrosis
This condition results from over wear or overtrimming at the toe tip. The resulting thin sole at the tip is more susceptible to deformation from stepping on stones or irregular features of the flooring. If a hematoma results at the toe tip it may lead to avascular necrosis of the soft tissues at the toe tip. If the lesion is open to the environment miscellaneous bacteria may invade and produce osteomyelitis or pathologic fracture of the tip of the third phalanx. Conservative therapy with a hoof block and cleaning of the toe tip usually results in a chronic state of infection and mild pain. Our current approach to this problem is to place a hoof block on the sound digit and amputate the distal portion of the affected digit. Either obstetrical wire or hoof nippers may be used to remove slices of the affected digit until all tissue exposed appears healthy. A tight bandage is applied over some antibiotic powder to control hemorrhage. The bandage is removed in a few days. There is no need for parenteral antibiotics. Regrowth of functional cornified epithelium will cover the partial amputation in about 1 month. The prognosis is excellent.
Amputation of one digit at the proximal interphalangeal joint or just above is a common procedure in cattle practice. After preparation a skin incision is made in the interdigital space and then beginning about 2 cm proximal to the interdigital cleft angling upward to a point on the lateral or medial side of the leg even with the distal margin of the accessory digit or dewclaw. All soft tissues can be sharply incised along the line of the skin incision. Obstetrical wire is then placed between the digits and the distal end of the first phalanx cut. If the cut misses this landmark and a portion of the second phalanx remains proximal to the cut it should be removed. If the articular surface of the first phalanx is intact it should be roughened with a knife. Alternatively, the digit may be amputated by sharp dissection to disarticulate the proximal interphalangeal joint. Some practitioners ligate one or two arteries and others simply use a very tight bandage. The cut surface of the removed portion should be carefully examined for evidence of sepsis or necrosis. If damaged tissue extends above the amputation and it is not debrided the outcome will be poor. After determining that all diseased tissue is removed, the surface of the wound is covered with an antiseptic or antibiotic dressing and a bandage applied to control hemorrhage. The bandage should be removed or changed in about 1 week if there was no need for maintaining drainage of septic regions proximal to the incision. If a tendon resection is performed the bandage should be removed in 2 or 3 days. Depending on the environment the cow must live in after surgery either no bandage is placed after the first one is removed or a light wrap to minimize painful contact with environmental objects. Parenteral antibiotics are usually given for 5 days.