Paw Tissues Unique; Injuries Need Special Care, Attention - DVM360

Paw pad injuries observed in dogs run the gamut from abrasions, blisters, ulcers and pressure callus formation, to burns, lacerations and avulsions accompanying distal limb degloving injuries. The canine footpad is a highly specialized tissue with specific and distinctive functions, and therefore, cannot be replaced by skin from the body. Wound management of these injuries is directed toward preserving as much of the pad tissue as possible and keeping pressure off of the affected paw to encourage wound healing, re-epithelialization and epithelial keratinization. This article will discuss management of two types of wounds commonly encountered by veterinary practitioners: paw pad abrasions and lacerations.

Photo 1: Deep pad abrasion with re-epithelialization in process.

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.

Dogs with the more superficial abrasion injury may have tags or flaps of superficial epidermis over the wound, which should be removed. However, these wounds are generally clean and require little if any debridement or lavage. More severe abrasion injuries with debris embedded in the tissues may require more management. These wounds should be surgically debrided to remove devitalized tissue. They should be lavaged copiously with 0.05 percent chlorhexidine diacetate solution. The lavage solution is expressed through an 18-gauge hypodermic needle attached to a 35-ml syringe. This is usually sufficient to dislodge debris and unattached tissue fragments from within a wound without traumatizing healthy tissue. Prior to bandaging, cotton pledgets may be placed in the interdigital spaces to maintain a dry environment.

Figure 1: Evaluating the depth of a paw laceration (A)Pad laceration does not appear to be deep due to apposition of deep pad tissues. (B) Laceration extends the full thickness of the pad, with contamination of pad tissues and the underlying area, including the flexor tendons. (C and D) Hemostatic forceps placed in the wound and spread to assess the depth of the wound. Credit: Swaim SF, Henderson RA: Small Animal Wound Management, 2nd edition, Williams and Wilkins, Baltimore, 1997, p. 336.

In superficial and deep abrasion and burn injuries, the goal is rapid epithelialization. With the superficial wounds, the tougher superficial epidermal layers are regenerated from the remaining pad epidermis. The deeper, i.e. full thickness skin wounds rely on re-epithelialization with a tough keratinized epithelium derived from intact pad skin at the edge of the wound. Thus, a portion of intact, full thickness pad tissue at the edge of these wounds is necessary for this type of healing. Epithelium derived from haired skin at the periphery of a pad will not suffice for pad replacement.