How To Assess And Manage Burn Injuries Of The Foot
Burn injuries are among the most devastating wounds a clinician may be asked to treat. Burn medicine is a critical care, specialized field of medicine, surgery and rehabilitation, all of which are intertwined and interdependent for successful outcomes. Precise awareness of modern wound management, skin function, infectious disease issues and crisis decision capabilities are hallmarks of burn injury care. Significantly, as more podiatrists become experts at wound management, many DPMs will find themselves becoming an integral part of the modern burn team. In the United States, there are approximately 125 recognized burn centers that admit a total of 22,500 burn patients annually. In the last 35 years, the severity and number of burn admissions has declined due in part to the more sophisticated training of burn clinicians, advances in pre-hospital emergency medicine and the evolution of wound medicine into a well-recognized medical and surgical specialty. Published reports indicate the number of deaths from burn sepsis has declined due to the improvement in antimicrobial dressings. However, in spite of promising advances, proper education of the public, other health care providers and community organizations would help reduce burn injuries and accidents even further. Who Do Burn Injuries Affect The Most? Who is prone to burn injury? These injuries tend to occur more with patients at extreme age levels, namely the elderly and the young. Forty-five percent of burn patients are children under the age of 8. Burns are the leading cause of death for those under the age of 2. Seventy-five percent of pediatric burn admissions are males and African-American children are three times more likely to be burned than Caucasian children. Socioeconomic issues are directly related to burn injuries, as they may result from living in more confined domestic quarters and less use of smoke detectors. “Reach and pull” scalding injuries are classic injuries incurred by young boys. One will typically see burns to the lower extremities and feet after a child reaches up to grab at the stove or table that has hot liquids or foods. Of the 100,000 scald burns recorded each year, there are reportedly 5,000 scald injuries to the feet. These injuries tend to be bilateral in presentation. Burn injuries to those age 65 and older result in a three- to fourfold higher mortality rate than younger patients who sustain critical burns. Poor agility, inability to "stop, drop and roll," preexisting medical conditions, atrophic skin, lack of smoke detectors and cooking with loose fitting clothing all predispose elderly patients to a more severe outcome. In regard to the death rate, clothing fires are the number one cause of death in this age group, due to smoking in bed and cooking with loose garments. Simply advising this group to cook with rolled-up sleeves can go a long way toward preventing burn injuries. Why A Strong Understanding Of Lower Extremity Skin Facilitates Appropriate Treatment Of Burn Injuries Burn management requires clinicians to have a full understanding of the layers of the skin and their function in order to assess the burn injury properly. (See “A Pertinent Primer On Skin Layer Function” below.) This, in turn, enables one to arrive at a more focused treatment plan. Anatomically, the dorsal skin of the foot is thin by design, facilitating the required gliding motion for the tendons to function without obstruction. Due to this inherent thin tissue, one must carefully assess the burns of the dorsum for tendon exposure. If you are dealing with exposed tendon, you need to rapidly determine the quality of the tissue. One can preserve healthy tendon via appropriate dressing selection, negative wound pressure therapy and properly timed skin grafting or other coverage procedures. Devitalized tissue warrants surgical excision in order to reduce the risk of infection from desiccated or necrotic tendon. Plantar foot burns are less common, due to the thicker skin layers as well as a unique fat pad construction. The thick tissue known as glabrous tissue is often uninjured in cases of bathtub scalds when a patient stands in hot water. The resiliency of this tissue is unique. When significant burns do occur to the plantar aspect of the foot, reconstruction is more challenging as attempts to recreate this anatomy designed for shock absorption and biomechanical stress is difficult at best. A Pertinent Primer On Skin Layer Function Skin serves as the barrier to water and vapor loss, and obstruction to pathogen entry into the body. It is the primary regulator of body temperature and is the largest organ in the body with an area of 20 square feet and a weight of 7 pounds. The epidermis, the more superficial layer of skin, varies in thickness between 0.04 mm on the eyelids to 1.6 mm on the plantar aspect of the foot. Histologically, there are five layers to the epidermis, although the stratum germinativum and stratum corneum are the more critical layers. Keratinocytes, originating in the germinativum, are the principal epidermal cells. They migrate to the skin surface every 28 to 45 days in a process known as cornification. This constant turnover of cells allows for a moist environment. Other cells in the mature epidermis are the melanocytes (pigment producing cell) and the Langerhan’s cells, which assist in the immune response. A healthy epidermis allows for rapid wound healing via constantly changing keratinocytes. Essentially two layers, the dermis is heavily vascularized and innervated. The superficial layer, the papillary dermis, is often called the “factory” where most of the dermis’ activity takes place. Primarily, the fibroblast is the most essential cell in the dermis. It is active in producing extracellular proteins, collagen and elastin. Collagen then undergoes maturation, cross-linking into strong tensile fibers and giving skin its tensile strength. Additionally, mast cells, macrophages and myofibroblasts are found in the dermis, as well as sensory-free nerve endings and receptors. Lastly, the epidermal appendages, hair and eccrine glands arise from the dermis and play a key role in the healing and re-epithelialization of superficial and partial thickness burns. A Guide To The Different Depths Of Burn Injury Patients can be exposed to the same temperature and sustain varying depths of injury. Indeed, the depth of the burn injury depends on a variety of factors. Age is extremely relevant. Children younger than 2 have thinner skin than adults and are therefore more susceptible to a deeper burn injury. The same is true of the older patient population. Starting at age 50, the skin starts to lose elasticity, suppleness and thickness. This aging process results in the translucent, fragile skin that one often sees among the elderly. As noted earlier, burn injuries to the dorsum of the foot may be deeper burns due to the inherent thinness of the skin. Contact time with the burning mechanism will also affect foot injuries. Water scalds versus cooking oil scalds on the dorsum will have different burn depth patterns, as the oil will result in a more prolonged heating insult than scalding water. Time of contact, the nature of the burning agent and location all influence the injury and the assessment. With this in mind, let’s consider the following degrees of burn injury. Superficial thickness burns. These are often referred to as first-degree burns. Since only the epidermis has been injured, there is no disruption of skin integrity. These injuries are characterized by pain and redness but there are no blistering or open wounds. One may see spontaneous healing within several days, and no hospitalization or specialty care is warranted. Partial thickness burns. Often referred to as second-degree burns, these burns are characterized by pain, redness, blistering and a wet appearance. These are the most common types of burns to the foot, resulting from the scald etiology. The dermis is involved and depth can vary from a superficial partial thickness burn to a deep partial thickness burn. These types of burns often warrant discussion by the burn team in terms of formulating a treatment plan. For example, there remains conflicting advice on blister care. Some experts advocate allowing the bullae to desiccate undisturbed while other experts advocate draining the burn blister and employing a topical antimicrobial dressing. Healing generally takes place in two to three weeks, absent a complication, and rarely mandates surgical intervention or grafting. Full thickness burns. These are burn wounds below the dermis. These are often referred to as third-degree burns when they extend into the subcutaneous tissue; fourth-degree burns if the injuries extend to muscle; and fifth-degree burns when the burns extend to bone. These burns are painless due to nerve destruction and are dry to touch. They may be white, black, gray, brown or red, and one may see coagulated or thrombosed vessels. These wounds require surgical debridement and excision as well as surgical skin coverage procedures for closure. Debridement options for full thickness burns may include tissue selective enzymatic agents such as Accuzyme, hydrotherapy and sharp scalpel excision. A new modality we have employed for wound and burn debridement is the Versajet Hydrosurgery system. This system enables one to use high stream water as a cutting scalpel or one can angle the position of the jet for debridement. Not to be confused with pulse lavage, the Versajet is a cutting device and requires training and practice before using it in the OR. Additionally, the Versajet combines debridement with a vacuum effect to collect airborne debris and contaminants from the wound site. The Versajet has allowed us to see a much clearer surgical field and better assess tissue quality without risking overzealous scalpel errors. Additionally, using high stream water greatly reduces the risk of wound bed or peri-wound trauma. Addressing Potential Complications When one undergoes surgery for a foot burn, there is a common and significant risk of a plantarflexion deformity of the hindfoot. One may see this result from prolonged bed rest or among critically injured patients who are ventilated and immobile. Fabricating a leg brace that can hold the foot in a 90-degree position to the leg is critical as iatrogenic equinus of the Achilles tendon is likely to develop without proper bracing and early suspicion of this complication. Digital edema is another complication that one often sees with foot and hand burn injuries. Edema is a major concern as cellular fluid in the normal cellular compartments begins to seep outside the cell walls due to capillary injury. Left untreated, the edema increases the risks of infection and vascular crisis, which may result in amputation. Providing digital compression around each digit is required in order to reduce the detrimental risks of edema. Many burn experts advocate that compression wrapping must go from the digit proximally to the groin in order to adequately control as much edema as possible. Contracture deformities of the MPJs and PIPJs are also common side effects of the burned foot with and without skin coverage procedures. One may see dorsal skin contractures after extensive debridement, tissue loss and coverage procedures. This must be monitored postoperatively for several years. One must explain bracing, aggressive physical therapy and serial skin plasty-contracture release procedures to the patient. Additionally, the burn team must determine when to permit early range of motion, out of bed activity and gait training. However, they must balance the risk of premature weightbearing with potential tissue loss versus delayed ambulation and activity that may further increase risk of edema and joint stiffness. There is no consensus on this matter and most authors concur this is one of the very delicate and difficult decisions required for a positive outcome. How Skin Grafts And Flaps Can Benefit Patients Challenging decisions also come into play in regard to skin coverage. Generally, one would obtain split thickness skin grafts (STSG) for dorsal foot burns. Meshed grafts facilitate better acceptance by the host as hematoma and seepage are less likely to gap between the bed and the graft. Additionally, one can harvest smaller grafts with the meshed STSG, reducing donor site issues of pain, scarring and healing. On the contrary, the meshed graft leaves a honeycombed appearance that bothers many patients, particularly females. In cases of massive tissue loss and in rare cases of the plantar full thickness burn, one must consider flap procedures. These procedures facilitate bulk coverage, especially on the inferior aspect of the foot. Local flaps require adequate vascular status as well as adequate non-burned tissue. In a free flap foot procedure, there must be enough healthy tissue available. Too often, when a flap procedure is indicated, it is due to the fact that a massive injury has destroyed the required excess skin and tissue to the lower extremity and foot. In these cases, one must consider obtaining transpositional flaps from non-injured proximal body regions. Lastly, optimal healing outcomes are not always likely. In the critically burned lower extremity, a primary amputation is often indicated in order to reduce the risk of limb sepsis and/or bacteremia. One should consider early amputation in cases of severe burn injuries that have destroyed vascular and nerve structures. In these cases, it can allow the patient an early and aggressive rehabilitation, and fitting for a limb prosthetic. What You Should Know About The Potential For Infection Burn wounds to the dorsum of the foot carry a high risk of cellulitis. Daily inspection of the foot is paramount in order to ensure that originally assessed partial thickness injuries are not converting into deeper wounds due to infection. Gram positive microorganisms remain the major pathogen in infected burn wounds with Staph aureus being the most common in early infections. One may see methicillin resistant Staphylococcus aureus (MRSA), as with diabetic wounds, among patients who have had a history of prolonged antimicrobial therapy without adequate burn wound care. Our center judiciously covers MRSA with linezolid (Zyvox, Pfizer) with the goal of early discharge from the hospital, which helps reduce the risk of nosocomial infections. A study from Alberta, Canada revealed the high incidence of Pseudomonas infection after 30 days of hospital stay, with the pathogen being introduced from the burn unit staff and environment.1 Indeed, clinicians must do everything they can to ensure immaculate attention to maintaining an infection-free wound environment, including being diligent and meticulous about hand washing and dressing changes. Doing these things can go a long way toward reducing the risk of nosocomial infections. Topical silver dressings are now available in numerous delivery systems and in different concentrations. Silver has long been recognized as an antimicrobial agent with broad spectrum antimicrobial effiacy against bacteria, fungi, virus, MRSA and vancomycin resistant Enterococcus (VRE) organisms. Topical silver serves a valuable role in burn injury care and clinicians must understand the role of silver and familiarize themselves with the different dressing selections. Final Notes In recent years, there have been major strides in burn and wound management treatment that have increased our ability to save lives and limbs once believed non-salvageable. With podiatric physicians playing a larger role in major teaching and tertiary care centers, it is reasonable to believe that DPMs will continue to be integral team players on burn care teams in the future. Dr. Cantor is an Attending Surgeon in the Burn And Wound Center at the Nassau University Medical Center in East Meadow, N.Y. He is also a faculty member of the Oxford University Wound Healing Institute in the United Kingdom. Mr. Burger is a Physicians Assistant at the Nassau University Medical Center in East Meadow, N.Y.
References 1. Oral presentation, Wound Healing Society, Atlanta, Ga. May 23-26, 2004.