Surgical treatment of a sloughed hoof by skin grafting in a young bull

Abstract

A sloughed hoof in a young bull as a sequela of foot and mouth disease was treated by skin grafting. Skin blocks obtained from the craniolateral thoracic area of the same animal were placed in slit-like pockets created on the coronary band. New hoof formation was completed within 20 weeks.

Sloughed hoof, the loss of the entire horny claw, is a rare condition in cattle. It may be caused by direct trauma (trapping the foot; infections, such as foot and mouth disease [FMD]; generalized intoxication, such as ergot poisoning; systemic vasculitis, such as that following infection with Salmonella dublin; and hereditary defective keratogenesis imperfecta [1–3]). Traumatic sloughing is a primary detachment, whereas sloughed hoof following epidermal disruption or infection is a secondary detachment. Both may be treated by removing the debris and bandaging the foot following application of topical therapeutics (antibiotic-impregnated petroleum jelly gauze) (1). Complete amputation of the affected digit may be indicated (4). However, there is little information on the long-term success of the various treatments.

Pinch grafts are small pieces of skin placed in a bed of granulation tissue, with regular spacing between the grafts, where the continuation of the skin has been disrupted (5). This report describes surgical treatment of a detached hoof due to FMD by autologous pinch skin grafting in a young bull.

A 10-month-old Holstein bull was presented to the Veterinary Teaching Hospital for severe lameness due to earlier FMD and with a history of dejection, dullness, and anorexia, accompanied by evidence of an acute painful stomatitis. The animal had chewed carefully and there had been abundant salivation. The saliva hung in long cords from the mouth. Vesicles had appeared on the feet (all 4 feet were involved), mainly in the clefts and on the coronet. Rupture of the vesicles had caused acute discomfort and severe lameness. Antiseptic (1% sodium hydroxide and 2% copper sulphate) and antibacterial treatment (penicillin and streptomycin) was not effective.

On arrival at the hospital, the bull was isolated in a separate room because of the contagious nature of FMD. The room was disinfected with mild alkali and fumigated, as required. Physical examination revealed a diffuse skin necrosis of the coronet that extended in a fuse proximodorsal direction to the metacarpal region. The bull was very uncomfortable on his feet, stepping from one foot to the other. He kicked or shook his feet when disturbed. By using pressurized clean water, all debris was removed. The lateral hoof capsule of the right front limb was macerated and partially detached, although the medial one was firmly in place.

Initially, the hoof of the lateral claw was not removed because it was thought that it provided some degree of protection for the germinative layer to produce a new hoof. Later, the degree of infection in the foot discouraged attempts at surgical intervention and oxytetracycline aged (Primamycin; Pfizer, Istanbul, Turkey), 30 mg/kg body weight (BW), IM, q24h for 5d, was administered. The foot was soaked once in 0.2% ethacridine lactate (Rivanol; Ulkem, Bursa, Turkey) solution for 30 min. A bandage containing nitrofurazone (Furacin; Eczacibasi, Istanbul, Turkey) was applied. The bandage was changed every other day for 7 d. Signs of infection eventually disappeared, but the claw detached and fell off, leaving the 3rd phalanx protruding from the ground surface of the lateral digit. At this point, grafting was elected.

The animal was sedated with xylazine (Rompun; Bayer, Istanbul, Turkey), 0.5 mg/kg BW, IM. The affected foot was desensitized by regional analgesia (nerve block) with 10 mL of 2% lidocaine HCl solution. Twenty small slit-like pockets, 2 to 4 mm in depth, were made in the granulation tissue. The pockets were made wide enough to allow the grafts to fit in. A cotton swab was placed into the pockets for hemostasis. The pockets were uniformly distributed with regular spacing between them in the tissue bed (Figure 1A). Under local anesthesia (2% lidocaine, 5 mL), skin from the ventro-lateral thoracic area, between the 7th and 8th costal space, where the skin is loose and thin (6), was prepared for grafting. The region was clipped and aseptically cleaned. The skin was pierced and elevated with a hypodermic needle, and the portion on the needle was cut free to form a split-thickness graft 1.0 × 0.5 cm. Twenty such grafts were obtained for placement in the prepared sites. At this stage, atraumatic surgical technique was used, where possible, to preserve the subdermal plexus and associated direct cutaneous vessels. Subcutaneous fat was removed from the grafts before each was inserted into a pocket.

Figure 1.

A. Pockets (▪) autologous skin grafts were seeded on the coronary band. Size: 1.0 × 0.5 cm. B. Dorsal view of the foot, 20 wk postoperatively.

From the contralateral side of the thorax, 3 strips of skin (approximately 3.0 × 0.5 cm) were obtained. The epidermal layer was inverted in a 100-mm culture dish, and as much of the dermis as possible was removed. The strips of epidermis and any adherent dermis were transferred to another dish and reduced to fragments of less than 1 mm³ by repeated mincing with a sharp scalpel. Single epidermal cells were recovered from the minced fragments with a solution of 1% collagenase and 0.25% trypsin in phosphate buffered saline, according to the method described by Rheinwald (7), to which 1% rifampin containing 10 mg lidocaine (Rifocin; Turk Hoechst, Istanbul, Turkey) was added. The corium of the digit was bathed in this solution containing isolated single cells for 30 min and then aseptically wrapped with an emollient ointment containing asiaticoside (Pomade Madecassol; Bilim Pharmaceuticals, Istanbul, Turkey). A wooden block was applied to the sound digit to keep the digit with the detached hoof off the ground. The bandages were changed as needed. The block and bandages remained in place for 4 wk. Donor sites were not dages sutured but left to heal as open wounds and sprayed with a combination of chlortetracycline HCl and gentian violet (Terramycine spray; Pfizer, Istanbul, Turkey).

Lameness resolved after 2 wk and the bull walked freely with minimal discomfort. Radiographs of the exposed 3rd phalanx showed no evidence of osteitis during the initial treatment. During the 5th postoperative week, a thin, glossy layer of new horn started to develop and was complete by the end of the 10th wk. However, the digit was not fully encased in normal mature horn until 20 wk postoperatively (Figure 1B). The owner reported no complications in the treated claw.

This case demonstrated that skin grafting following detachment of the hoof and disruption of the coronary band improved the development of new horn. In cattle, once formed, the wall passes slowly down over the front of the foot at a rate of approximately 5 mm/mo. As the distance from coronary band to the wearing surface at the toe is approximately 75 mm, new horn will not come into wear until 15 mo after it has first been produced (8). The interval was shortened in this case, however, since the complete production of horn required only 20 wk, possibly because the use of isolated epidermal cells, an emollient agent (asiaticoside), and skin autografting promoted and accelerated the healing process. The regeneration process started to overtake the degeneration process on the grafting field on the 5th d and was more evident by the 8th d. It was thought that the pinch grafts provided a germinal source for production of the new pododermal structures.

Graft survival depends on early reestablishment of sufficient circulation to provide nutrition and dispose of metabolic products (9). The coronary band possesses a large concentration of capillaries that could have provided adequate blood supply for the pinch grafts, which may explain why the grafts were readily accepted by the recipient bed. In this case, the grafts were viable on the 5th d following surgery and remained in place until healing.

Rifampin has widely been used in human (10) and veterinary (11) medicine for soft tissue infection, and it can be useful locally for the treatment of infected digits in cattle.

In this author’s experience with a limited number of cattle with sloughed hoof, amputation has not been encouraging. It should be the last treatment considered, because amputation may cause loss of body weight, infection or ulceration of the remaining claw, and necrosis of the proximal portion of the middle phalanx, associated with accidental resection of the nutrient artery supplying the bone, leaving the remaining bone without an adequate blood supply (12). Protection and proper immobilization of the wound, especially in the foot, are salient considerations to prevent fecal contamination and accumulation of moisture.

The advantages of the technique used here were as follows: a) the obtaining of pinch grafts was simple and required no special equipment, b) graft survival was good, c) grafts were obtained under local anesthesia, and d) healing of the donor site was uncomplicated.

The skin grafting and vigorous treatment reported here provides a valuable contribution for success and should encourage clinicians to consider autologous skin grafting for the treatment of detached hooves in young bulls. CVJ