Paw tissues unique; injuries need special care, attention
Abrasions and burns The less severe form of abrasion injury results in loss of stratum corneum from a pad. This can result from prolonged contact of the pad with a rough surface, during movement. These wounds are commonly observed in sporting dogs and working dogs. The wound leaves the deeper, more sensitive layers of the epidermis exposed. In the more serious form, the shearing force generated between the two surfaces (pad and ground) strips paw pad epidermis and partial or full thickness dermis. With full thickness skin loss, the underlying fibroadipose tissue of the pad is exposed (Photo 1). Dogs dragged behind motor vehicles have this type of injury. Chemical and thermal, superficial pad burn wounds may present a similar clinical picture with varying loss of epidermis and dermis.
A protected, moist, nonadherent wound surface devoid of pressure is important to promote rapid re-epithelialization. Topical dressings such as Acemannan hydrogel, silver sulfadiazine cream or a neomycin-bacitracin-polymixin (Neosporin) ointment known epithelialization stimulants, may be sparingly applied to the wound surface. A nonadherent, semiocclusive, primary bandage layer followed by a thick layer of absorbent, secondary bandage wrap and a tertiary, two-inch porous adhesive tape layer, complete the bandage. If there is concern about the bandage causing pressure over the carpal pad or the point of hock, a modified "donut" bandage made of four to five folds of cotton cast padding material with a hole cut in its center, can be placed over the carpal pad or the point of the hock and incorporated into the secondary absorbent bandage layer. The cup portion of a Mason metasplint cut to size is incorporated within the bandage under the palmar/plantar surface of the paw, especially with deeper wounds. Initially, daily wound dressing and bandage change is necessary. This assures replacement of active drug on the wound surface.
Non-adherent bandage therapy plays a pivotal role in abrasion wound management as it provides an optimum environment for re-epithelialization. Medications that stimulate re-epithelialization and proper bandage padding also enhance abrasion and burn injury healing. Improper bandaging techniques may result in impaired healing.
Paw pad lacerations Pad laceration is a wound resulting from tearing of pad tissue. Lacerations may be full or partial thickness. Management of such a wound is dictated by the depth and loss of tissue from that wound. Sharp edges on objects, such as glass, metal and occasionally stone and lawn edging are capable of creating such wounds when a dog accidentally steps on them. Most of these are highly contaminated wounds owing to their anatomical location, especially if the dog persists in placing the paw on the ground after wound infliction.
With the blades in the closed position, a pair of sterile, hemostatic forceps is introduced into the wound. The blades are then opened to spread the wound and gauge its depth. This helps assess full thickness or partial thickness involvement of the pad. With full thickness lacerations, digital flexor tendons may be visible (Figure 1, p. 17). The distal limb is routinely prepared for aseptic surgery. The hair on the paw is clipped as far proximal as the distal antebrachium or just proximal to the hock. Special attention is paid to clipping hair within interdigital spaces, followed by a surgical scrub of the area using chlorhexidine scrub. This is followed by followed by surgical debridement of any necrotic tissue and thorough lavage using 0.05 percent chlorhexidine diacetate solution as described in the previous section, to dislodge any dirt and contaminants present. If the wound is a full thickness pad laceration, a 1��4-inch Penrose drain may be placed under the pad tissue, exiting through and anchored to the skin adjacent to the pad (Figure 2). Deep, simple interrupted sutures using absorbable material such as 3-0 polydioxanone or polyglactin 910 should be placed in the fibroadipose tissue of the pad to help appose the deeper layers. The superficial, keratinized layer of the pad tissue is apposed using 3-0 nonabsorbable materials such as polypropylene or nylon in a far-near-near-far suture pattern. This pattern achieves apposition while distributing the tension away from the suture line. Segments of cotton are placed within the interdigital spaces to maintain a dry environment. Nonadherent pad may be used as the primary bandage layer. A modified "donut" bandage, as previously described, may be placed over the carpal pad or the point of hock if there is concern about the bandage placing pressure over these areas. This is incorporated into the secondary, fairly thick, absorbent gauze wrap, followed by a tertiary, porous, two-inch adhesive tape layer. It is important to keep weight off of a sutured paw pad while it heals. One of the two types of bandage can be used for this. First, a "donut" type bandage can be used whereby a foam sponge is cut to shape of the palmar/plantar paw surface, with a hole is cut in the sponge at the area overlying the sutured wound (Photo 2, p. 17). Incorporating this in a bandage distributes pressure around a wound. This could be used on small to medium sized dogs or lacerations that are not severe. For large dogs or major pad wounds, a "clam shell" bandage/splint should be considered. It acts as a localized crutch. After bandage placement, a Mason metasplint is placed on the cranial and caudal bandage surfaces such that they extend by 1 inch beyond the very distal end of the paw, with the cups of the splints facing each other. These are taped to the bandage (Photo 3, p. 17). Short of bandaging the leg up with the stifle joint flexed, the "clam shell" bandage / splint keeps pressure off of the pads most efficiently.
Paw pad lacerations allowed to heal by first intention show earlier increased tensile strength of the pad tissue and decreased scarring when compared to those allowed to heal by second intention. Pads spread when weight is borne on them, causing the fibroelastic dermis to stretch. If lacerations are not sutured and are not bandaged to keep weight off of the tissue, weight bearing spreads the tissue and delays healing. Along the same line, if a sutured wound is not bandaged to keep weight off of the pad, weight bearing causes the pad tissue to spread, the sutures to tear through tissue and therefore, delayed healing.
Paw pad abrasions, burns and lacerations are common paw injuries presented to practicing veterinarians. Due to the uniqueness of paw pad tissue, its injuries are managed differently.