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Surgery of the diseased bovine digit (Proceedings)
Anesthesia 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).
Deep Sepsis of the Digit
Untreated or late-treated foot rot, complicated sole ulcer, 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 Digit
Anesthesia 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.
Flexor Tendon Resection
If, after amputation, it is evident that sepsis extends proximally along the deep flexor tendon it should be resected. A 3 cm incision parallel to the path of the tendon is made over the affected branch of the flexor tendons beginning just proximal to the accessory digit. There is strong fascia surrounding the sheath of the combined superficial and deep flexor tendons. In fact the superficial flexor tendon forms a tube around the deep at this level. Sharp dissection oriented along the skin incision through the superficial flexor tendon will reveal the deep flexor tendon. The deep flexor tendon is grasped with a strong instrument such as a dental extractor or exteriorized with the aid of curved hemostats. There may be adhesions of the deep flexor tendon to surrounding structures at the level of the distal transaction which require sharp dissection. In some cases the tendon will simply be pulled to the outside from the proximal incision. The deep flexor tendon is transected at the most proximal exposed part and surgical drainage tubing placed through its original course to exit at the distal incision. It may be knotted into a loop or each end affixed by suture. One or 2 skin sutures are placed in the proximal incision. Systemic antibiotics are routinely given for 5 days. The drainage tubing is removed in 2 weeks.
White line abscesses near the heel, penetrating foreign bodies, and deep flexor tendon avulsion or fracture of the flexor process of the third phalanx all may result in severe lameness with extensive painful swelling of the heel region of a single digit. Following anesthesia and standard surgical preparation an incision is made into the heel bulb. The choices are a vertical incision extending into the sole (after paring away enough sole at the heel so that it is thin enough to make an incision with ordinary surgical instruments) or a transverse incision in the middle portion of the cornified heel. Exploration of the cavity encountered will dictate further steps. If the limits of the abscess or hematoma do not involve the navicular bursa or deep flexor tendon the prognosis is excellent and resolution should be prompt. The cavity is flushed with water and mild disinfectant such as povidone iodine. A surgical drain is inserted in the wound and affixed with sutures. Antibiotic powder is placed in the cavity and the incision closed with a few skin sutures. A hoof block should be placed on the healthy digit. If the condition resulted from mechanical disruption of the deep flexor tendon or an avulsion fracture of the third phalanx there is risk of involvement of the navicular bone and bursa. If no sepsis is evident, the outcome should be satisfactory. The cow will probably need the hoof block renewed in 1 month but no further treatment is necessary.
Septic Distal Interphalangeal Joint
When the distal interphalangeal joint is septic there is enlargement of the joint space and distension of the joint capsule. This may be observed as painful swelling at the coronary band in the caudal third of the abaxial coronet. It is possible to insert a needle into the joint capsule through the coronary band to verify the nature of the joint contents. In those cases where there is no swelling of the heel or deep flexor tendon a simple fenestration of the joint may result in a satisfactory cure following ankylosis of the joint. The most common means of this sepsis occurring are secondary to foot rot or to a complicated sole ulcer. In either case, after anesthesia and cleaning the sole, if it is intact, a 7 to 12 mm (3/8 to 1/2 inch) drill is used to fenestrate the joint. Beginning in the typical site for sole ulcer the drill is directed in a sagital plane to exit the digit just at the coronary band on the dorsal surface. This will satisfactorily provide drainage of the joint. Surgical tubing or braided nylon rope is passed through the drilled hole and tied around the abaxial side of the hoof. A block is placed on the healthy digit and systemic antibiotics given for 5 days. The drain is removed in 2 weeks. Full ankylosis requires several months but the cow will usually be sound without a block in 1 month.
Extensive Deep Sepsis of the Digit
Amputation is an acceptable therapy for extensive deep sepsis of the digit. However, claw sparing procedures have been adapted for field use that provide excellent results. We have combined the transverse heel incision described above with drilling through the distal interphalangeal joint, navicular bone resection, and deep flexor tendon resection to resolve some extensive problems with deep sepsis. A hoof block should be applied before beginning surgery. The approach is as for retroarticular abscess but includes incising deeply just proximal to the navicular bone. This will transect the deep flexor tendon if it is still intact. Through the same skin incision a more distally directed incision is made to cut the distal attachments of the navicular bone and remove a wedge of tissue. In some cases the navicular bone and its attachments are so necrotic that it has already disappeared or is easily removed through this incision. If the collateral ligaments are intact and difficult to incise, use a 5 mm (1/4 inch) drill to make a hole in the center of the navicular bone. Into this hole insert a stout metal rod or screwdriver to fracture the bone into 2 pieces. Each piece can then be grasped and twisted to rupture any remaining attachments. A useful inexpensive tool for this procedure is a canine dental extractor. If the flexor tendon is necrotic or septic it should be resected as described above. Use a 7 to 12 mm (3/8 to 1/2 inch) drill to fenestrate the distal interphalangeal joint through the incision. To exit at the coronary band it will be necessary to overextend the distal interphalangeal joint. Surgery tubing should be placed through the joint and secured in a loop around the axial side. If tendon was resected a drain should be placed there as well. If there was an existing fistula that is not connected to the transverse heel incision it should also have a surgical drain. Once all drains are in place antibiotic powder is placed in the heel incision and the incisions closed with a few skin sutures. Parenteral antibiotics should be given for 5 days and all drains removed in 2 weeks. I do not recommend wiring the toes of the 2 digits together as is done by others. The intended ankylosis of the distal interphalangeal joint will proceed more quickly if there is no motion in the joint. If the digits are fastened together every step will cause motion of the joint receiving surgery. The block may need replacement at 1 month.