Thermal Injuries to the Extremities

Transcription

1 Orthopaedic Surgery Board Review Manual Statement of Editorial Purpose The Hospital Physician Orthopaedic Surgery Board Review Manual is a study guide for trainees and practicing physicians preparing for board examinations in orthopaedic surgery. Each manual reviews a topic essential to the current practice of orthopaedic surgery. Thermal Injuries to the Extremities Series Editor: Pedro K. Beredjiklian, MD Associate Professor of Orthopaedic Surgery, Thomas Jefferson University Hospital, Philadelphia, PA; Chief, Division of Hand Surgery, The Rothman Institute, Philadelphia, PA PUBLISHING STAFF PRESIDENT, Group PUBLISHER Bruce M. White Senior EDITOR Robert Litchkofski Contributors: Michael Rivlin, MD Instructor, Thomas Jefferson University Hospital, Philadelphia, PA Annamaria Tiba, MD Assistant Professor, Department of Dermatology and Allergology, University of Szeged, Hungary Jonas L. Matzon, MD Instructor, Rothman Institute, Thomas Jefferson University Hospital, Philadelphia, PA executive vice president Barbara T. White executive director of operations Jean M. Gaul Table of Contents NOTE FROM THE PUBLISHER: This publication has been developed without involvement of or review by the American Board of Orthopaedic Surgery. Introduction...7 Burn Injuries Freezing Injuries Electrical Injury Chemical Burns...23 References Hospital Physician Board Review Manual

2 OrthopAedic SurgEry Board Review Manual Thermal Injuries to the Extremities Michael Rivlin, MD, Annamaria Tiba, MD, and Jonas L. Matzon, MD Introduction The skin is the organ through which we interact with our environment. This resilient and incredibly adaptive structure can often maintain its integrity through harsh internal and external physical insults, but exposure to thermal extremes can rapidly damage healthy skin. The acral surfaces in particular are at risk from injury due to exposure to the elements encountered during recreational and vocational activities or simply during everyday life. These thermal injuries have a wide spectrum of presentations, physiologic effects, and patient outcomes. Minor burns are frequent occurrences that often have little lasting morbidity, while major thermal injuries can be life-threatening, with an overall mortality rate of 4%. 1 This manual discusses the body s reaction to the damaging effects of extreme temperatures and agents that may have a burn-like effect on the skin, and also reviews the presentation and management of thermal injuries seen in orthopaedic practice. Burn Injuries Burn injuries to the extremities are frequently encountered, as people often come into contact with hot surfaces or materials when interacting with the environment. It is not surprising that common household burns comprise the majority of burn injuries seen by health care providers, since most burns occur at home. 1 These include kitchen injuries, such as those caused by spilled boiling liquids and contact with cookware or cooking surfaces, as well as house fires, which account for a lesser proportion of patients presenting with burns but often involve a larger portion of the body s surface area. Burns can cause a wide spectrum of effects, from a minor skin irritation, such as mild sunburn, to a life- and limb-threatening injury from a high temperature burn. The severity of burns depends on a multitude of host and heat-source factors. Host factors include the body s vulnerability and adaptability. Patients at the extremes of age often have little physiologic reserve, and therefore smaller insults may create more devastating outcomes. 2 Comorbid conditions, associated injuries, and resuscitation delays exaggerate the morbidity associated with burns. 3,4 However, the major determinant of burn severity is depth and extent. 5 These variables are dependent on heat-source factors, including temperature, heat capacity, surface area, and duration of contact. Copyright 2012, Turner White Communications, Inc., Strafford Avenue, Suite 220, Wayne, PA , All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, electronic, photocopying, recording, or otherwise, without the prior written permission of Turner White Communications. The preparation and distribution of this publication are supported by sponsorship subject to written agreements that stipulate and ensure the editorial independence of Turner White Communications. Turner White Communications retains full control over the design and production of all published materials, including selection of topics and preparation of editorial content. The authors are solely responsible for substantive content. Statements expressed reflect the views of the authors and not necessarily the opinions or policies of Turner White Communications. Turner White Communications accepts no responsibility for statements made by authors and will not be liable for any errors of omission or inaccuracies. Information contained within this publication should not be used as a substitute for clinical judgment. Orthopaedic Surgery Volume 8, Part 5 7

3 Table 1. Classification of Burn Wounds Classification Depth Characteristics Healing First degree Superficial Epidermis Erythema, mild edema 2 3 days Second degree Superficial partialthickness Epidermis and superficial dermis Blisters, marked edema, erythema 5 21 days Deep partial-thickness Epidermis and deep dermis Thick-walled blisters, blanched skin 3 weeks Third degree All layers of skin Blue-gray discoloration, hemorrhagic blisters None Full-thickness Fourth degree Deep tissue involvement Deep necrosis to muscle, tendon, bone None Pathophysiology Following contact with a heat source, the skin and subcutaneous tissues undergo physiologic changes on the cellular level. Jackson 6 described 3 zones of injuries that propagate following thermal injury. From the center of the insult to the periphery, they are the central contact area, the inner ring, and the outer ring. At the central contact area, coagulation necrosis begins with rapid cell death secondary to the physical insult. This area may appear white, yellow-brown, or charred, and tissue damage is irreversible. The inner ring in the concentric pattern of cell injury is initially hyperemic but progresses to an avascular, pale border, which eventually becomes necrotic. This area is characterized by vascular stasis and is referred to as the zone of ischemia. Here, early apoptosis and delayed necrosis occur due to multiple factors, such as free radical damage, tenuous tissue perfusion and oxygenation, microthrombosis, and cytokine changes. Eventually, this leads to progression of the necrotic margin. 7 The damage in this area is hypothesized to be reversible, and therefore much recent research has focused on how to prevent further tissue injury. 8 Finally, the outer ring of erythema is a highly vascular and edematous region, where healing tissue begins to form and to expand towards the center of the injury. Healing of burns depends on the depth of tissue involvement. Superficial burns involving the epidermis and papillary epithelium regenerate from the intact epithelial appendages, which allows normal healing with minimal scarring. 9 Deep partial-thickness burns have variable healing response. These wounds may undergo re-epithelialization from progenitor cells that were spared in the deep areas of the papillae of the dermis. If the burn involves deeper layers where there are no cell lines that can aid in regeneration, or if the tissue damage is full-thickness, healing potential is minimal without surgical intervention. Diagnosis When treating burns, proper wound evaluation and characterization are required. Tissue damage is a constantly evolving process. Frequent reexamination is necessary, and reclassification of wound injuries helps the physician tailor the treatments and interventions to the needs of the patient. Classification by Depth A common way of describing burn wounds is based on the depth of the injury and relates to the tissue layers affected. Dupuytren was one of the first clinicians who classified burn wounds in terms of depth of tissue injury, and his work is the basis of today s wound evaluation in burn patients. 10 The most widely used current classification has 4 grades, expressed as degrees, and is based on clinical evaluation (Table 1). However, most 8 Hospital Physician Board Review Manual

4 A B C D E Figure 1. Four grades of burn injury classified by depth of injury. (A) First-degree burn surrounding second-degree burn blister formation. (B) Second-degree, superficial partialthickness burn, ruptured bulla. (C) Second-degree, deep partial-thickness burn. (D) Third-degree burn. (E) Fourthdegree burn over distal interphalangeal joints with burned joint exposed over the long finger. (Images courtesy of Professor Lajos Kemeny, MD, PhD, DSc.) burns have areas of variable depth of involvement and have a combination of several grades. When describing burn injuries, the highest degree takes priority and is used in the classification. First-degree burns (combustio erythematosa) are characterized by superficial tissue damage and involve only the epidermis (Figure 1). The most common form of first-degree burn is sunburn, which appears as erythematous discoloration of the skin without blister formation or desquamation. Mild edema of the skin is noted. The involved areas are tender and very sensitive, but the skin barrier is Orthopaedic Surgery Volume 8, Part 5 9

5 uninterrupted. Therefore, first-degree burns do not predispose patients to infections. Some superficial sloughing may occur, but these burns will usually heal without scar in less than a week. Sensory modalities are unaffected long term. Second-degree burns (combustio bullosa) are more extensive with deeper tissue involvement than first-degree burns. The involved areas are exquisitely tender, red, wet, and markedly edematous. Second-degree burns are further subclassified as superficial partial-thickness and deep partial-thickness. Superficial partial-thickness burns produce a characteristic blistering appearance (Figure 1B). The blisters are covered with a thin layer and contain initially clear and later cloudy fluid. The blisters form from fluid collecting between the dermal-epidermal junction, which has been damaged by the heat. As the epidermis separates and lifts off, high colloid pressure exudates accumulate. This draws additional fluid by osmotic gradient and enlarges the collection. Deep partial-thickness burns involve the deeper dermis (reticular dermis; Figure 1C). These wounds appear white and pink with thick-walled, usually ruptured bullae, and there is blanching of the superficial layers. Pressure sensation is intact, whereas pinprick sensation and two-point discrimination may be absent. Healing is variable but usually takes around 3 weeks. Third-degree burns (combustio escharotica) are characterized by complete disruption of the epidermis and dermis. These areas often appear charred or white (Figure 1D) and are completely insensate, dry, and hardened. With time, the edges of the burns demarcate and the eschar separates. Recovery proceeds with contraction of the surrounding tissues without actual healing of the areas of full-thickness burn. Fourth-degree burns involve both the skin and the underlying tissues, such as fat, fascia, muscle, tendons, bones, or joint (Figure 1E). The irreversible damage is extensive and difficult to assess initially. Since spontaneous recovery does not occur, extensive debridement and reconstructive efforts are required to reduce the serious morbidity that these injuries carry. A similar classification system by burn depth that is based on more descriptive anatomy is sometimes preferred. Superficial partial-thickness burns include first-degree and superficial second-degree burns, which involve the epidermal and possibly the upper dermal layers of skin. Deep partialthickness burns are equivalent to deep seconddegree burn and involve the epidermis and part of the dermal layer. Full-thickness burns are thirdand fourth-degree burns, and they involve the entire epidermis and dermal layers. It is important to keep in mind that clothing and other melted materials can make the characterization of wounds extremely difficult (Figure 2). Classification by Severity Other than depth, burns can be classified by severity (Table 2). 11 Burn injury is referred to as minor when less than 15% of total body surface area (TBSA) is involved in adults and less than 10% of TBSA in children. Less than 2% of TBSA can be full-thickness burns. Sensitive areas that would produce major morbidity (ie, face, hand, foot, genitalia) are not involved. If no comorbid exacerbating factors exist, these injuries are generally safe to manage on an outpatient basis. Patients with moderate burns have partial-thickness wounds involving between 15% and 25% of TBSA. In children under 10 years old and adults over 40 years old, involvement is between 10% and 20% of TBSA. Less than 10% of TBSA can be 10 Hospital Physician Board Review Manual

6 Table 2. Classification of Burn Severity Category of Burn Injury Total Body Surface Area Age years Age <10 or >40 years Full-thickness (all ages) Minor <15% <10% <2% Moderate 15% 25% 10% 20% 2% 10% Major >25% >20% >10% full-thickness burn. These patients do not have any involvement of their hands, feet, face, or genitals, and do not otherwise qualify for transfer criteria to a burn center according to the American Burn Association (Table 3). 12 Moderate burn injuries are generally more serious and require inpatient medical care. Care for these burns should be provided by physicians who routinely treat these types of injuries. Although patients with moderate burns may need additional medical resources, they do not always require transfer to a burn center. Major or critical burns are when adults have partial-thickness burn involving more than 25% of TBSA or full-thickness burn involving more than 10% of TBSA (more than 20% partial-thickness burn in children under 10 years old and adults over 40 years old). These patients require burn center care. Patients that fulfill the American Burn Association transfer criteria are automatically considered to be major burn victims. This category also includes patients with electrical burns, chemical burns, major trauma, inhalation injury, and serious comorbid conditions. Classification by Size Although there are multiple schematic illustrations and guides to approximate TBSA involvement, many shorthand ways of approximating wound size exist. The Lund-Browder diagram is an accurate way to classify injuries by size. 13 For quick Figure 2. Patient with clothing burned on skin. (Image courtesy of Professor Lajos Kemeny, MD, PhD, DSc.) Orthopaedic Surgery Volume 8, Part 5 11

7 Table 3. The American Burn Association Burn Center Transfer Criteria >10% total body surface area (TBSA) of second- or third-degree burns in patients younger than 10 years or older than 50 years > 20% TBSA second- or third-degree burns in persons of other age-groups > 5% TBSA of third-degree burns in persons of any age-group Second- or third-degree burns that involve the hands, feet, face, perineum or genitalia, or major joints Electrical burns, lightning victims Chemical burns Inhalational injury Medical comorbidities that would impact burn care Major trauma or fractures System requirements are not met at the present facility (ie, availability of pediatrician in a pediatric burn, long-term rehabilitative resources not available, complicating social circumstances like cases of substance abuse or child abuse) approximation, Wallace 14 developed a scheme that adds a proportion-value to areas of the body, commonly referred to as The Rule of 9 s (Figure 3). As a rough estimate, the palm is approximately 1% of the body surface area. These methods are quickly and easily applied, but they are not precise. Therefore, for longitudinal follow-up of evolving tissue involvement, more detailed maps of individual wounds are recommended. Inhalation Injury Inhalation injury is caused by thermal and particulate (soot) damage to the upper airway. The physiologic effect of this type of injury profoundly affects survival and morbidity in burn patients. A high index of suspicion is required to diagnose and properly manage these insults early. An almost 30% increase in mortality is attributed to inhalation injury in the setting of burns. 15 External clues such as coughing, black sputum, or soot/singeing of the mouth, nose, hair, and/or face can aid in diagnosing the underlying upper airway damage. Heat can disrupt the fine lining of mucous areas of the oropharynx and the ciliated lining in the upper to lower airways. In addition, combusted particulate matter (soot) may serve as a mechanical irritant causing bronchospasm or congestion of the lower airways. Noxious gasses (eg, carbon monoxide, cyanide, chloride gas, fluorocarbons) released by the combustive reaction further exaggerate the hypoxic state. Most patients with inhalational injuries do not present in distress but rather develop it over the course of the next several hours as edema of damaged tissue develops. Anticipating these events through proper airway evaluation can minimize the significant comorbidity. Management The management of burn patients is very complex. In the past few decades, the primary goal for minimizing burns has shifted toward prevention. Sophisticated fire-resistant building materials, firesafe architecture, sprinkler and alarm systems, escape protocols, and improved 911 response have all been instrumental in minimizing fire risk. If a victim is exposed to a heat source with the potential for injury, extrication and efforts to minimize exposure must be undertaken while keeping rescuers protected. Once the patient is in a safe environment or transferred to a hospital setting, a primary survey is initiated according to the current 12 Hospital Physician Board Review Manual

8 BLS (Basic Life Support), ACLS (Advanced Cardiac Life Support), ATLS (Advanced Trauma Life Support), and ABLS (Advanced Burn Life Support) protocols, in order of escalation. Proper resuscitation and nutritional support are essential for a successful recovery. A thorough evaluation for inhalation injury is paramount as the presence of such an injury significantly increases mortality. In these settings, meticulous pulmonary toilet, continued oxygen therapy, and a low threshold for intubation are recommended to minimize these risks. A burnspecific secondary survey must include the evaluation of all wounds and affected areas. Clear and detailed documentation of burn location, size, and severity is required. All wounds have to be sized and evaluated and a map must be created detailing the patient s injuries and stages of the wounds according to the classifications discussed above. Transfer to a Burn Center Upon initial evaluation and resuscitation, an important decision has to be made determining where the patient s definitive care should take place. Proper facilities and qualified specialists are required to guide the often complex and resource-heavy care of burn victims. Burn patient care is very complex and should be managed by physicians who routinely treat these injuries. Burn severity classification, discussed above, aids in determining the appropriate setting required in treating the burn victim. The American Burn Association set forth guidelines that help with decision making around which patients need transfer to a burn center (Table 3). 12 In the orthopaedic practice, it is necessary to know specific presenting signs that would require transfer. These include wounds that are at least partial-thickness and involve the hands or feet. Furthermore, patients who have a fracture, open joint injury, burn over a major joint, *Children: Head 18% Leg 14% Palm 1% Figure 3. Rule of 9 s. Ant: 9% Post: 9% 18%* 9%* 9% Ant: 9% 9% Post: 9% 1% 18%* traumatic injury, or medical comorbidities should be transferred to a burn center. Initial Treatment The key in burn wound management is continuous reevaluation and interventions tailored to the individual patient. The guiding principle of surgical management is the depth of burn wounds. Goals of wound management and burn surgery are to achieve rapid wound healing with a cosmetically appealing result, while avoiding infection, contracture formation, and excessive scarring. 5 Orthopaedic Surgery Volume 8, Part 5 13

9 Localized minor burns are often self-treated or managed by primary caregivers, such as emergency room physicians and general practitioners. Initial cooling of the affected area decreases inflammation, erythema, and swelling. Evidence suggests that tap water or saline at 8ºC (46ºF) is as effective as any other means of dissipating heat from the burn area. 16 Thorough cleaning of the contaminated wound is recommended to remove dirt, debris of clothing, or burned on textiles. This may be accomplished with room-temperature water or saline with mild soap or chlorhexidine gluconate solution. Other substances and surfactants have been used for initial decontamination, such as Poloxamer 188 and Medi-Sol Adhesive Remover. Blister management has long been a controversial area in the treatment of second-degree burns. Proponents of blister debridement argue that the toxic and procoagulant milieu of these blisters exerts an unfavorable effect on the recovering tissues while creating a harboring medium for pathogens that may lead to infection. 17 On the other hand, many physicians, including the authors, argue that intact blisters serve as biological dressings. Leaving the bullae intact aids in pain control by providing coverage to an open wound, and also keeps bacteria walled off in the outside environment. 18,19 If blisters are tense, confluent, and large, such that they restrict range of motion or constrict distal blood supply, needle decompression will decrease their size while still providing pain relief and retaining the biological dressing. Since even minor burns are susceptible to tetanus, the patient should have the appropriate standard immunologic coverage or confirmation of immunization status. In general, antibiotic prophylaxis is currently not recommended for patients with severe burns. 20,21 Wound surveillance and serial examination is the most sensitive way of diagnosing wound infections. Wound Sepsis Due to the disruption of the patient s normal barrier to the external environment, infection and septicemia are the most common complications in hospitalized burn patients. 1 Wounds should be evaluated and followed closely. Signs of wound infection may be subtle. Pigmentation, exudates, erythema, and conversion of partial-thickness to full-thickness burns may all be signs of infection. Swabbing and culturing open wounds should be avoided as it is likely to yield misleading results that may represent normal flora or a contaminant. If infection is suspected, biopsy should be obtained using surgical principles. A finding of 10 5 organisms per gram of specimen is indicative of infection. Concurrent positive blood cultures with the same organism further increase the specificity of the biopsy. The common organisms that colonize burns and lead to infections are Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus [MRSA]), Streptococcus pyogenes, Acinetobacter baumanniicalcoaceticus complex, Pseudomonas aeruginosa, and Klebsiella species. Several of these organisms, specifically Streptococcus and Pseudomonas, produce toxins that can cause toxic shock syndrome. Fungal infection of the burn wounds is also prevalent, especially if topical antimicrobials that do not have antifungal coverage are used. Wound Care and Dressings Exposed wounds should be kept sterile and moist, preventing fluid loss and infection. Dressing changes should continue until healing has progressed to the point when the patients own skin is able to provide adequate protection from the environment. If wound closure does not occur 14 Hospital Physician Board Review Manual

10 with conservative treatment, surgical wound management may be necessary. Dressing changes are recommended at least daily, with increased frequency to twice a day for higher-risk or infected wounds, as well as those that saturate dressings more frequently or require repeated debridement. There are numerous dressings, applications, and membranes available for burn wound management. The clear advantage of one over the rest has not been demonstrated in the literature. Simple wounds should be cleaned and covered with a nonadherent dressing with a more absorbent layer on top. Antimicrobial preparations applied to the skin during dressing changes can help prevent infection and set up the optimal environment for skin healing. Although there are many options available, silver-containing topical solutions have been a gold standard. The broad-spectrum antimicrobial properties of silver protect against a wide range of microbes, including resistant strains, such as MRSA and vancomycin-resistant enterococci, and many fungi. 22 Silver sulfadiazine 1% cream has variable gram-negative bacteria coverage, but good gram-positive bacteria and yeast coverage. It does not cause significant discomfort to the patient during or after application, nor does it alter the appearance of the wound significantly, like other applications that may discolor the skin. However, it can form a thick exudate when mixing with wound drainage, which can make it difficult to clean off. Furthermore, it should not be used on patients with a sulfa allergy or on women who are pregnant or lactating. By its mechanism of action, it halts epithelialization and should be stopped when re-epithelialization is noted. Other antimicrobial chemotherapeutic agents may be used as alternatives to silver sulfadiazine. Silver nitrate, which has good gram-negative bacteria, gram-positive bacteria, and yeast coverage can be substituted. As with silver sulfadiazine, it is painless to apply, but it may discolor the wound, which can make assessment challenging. Unlike silver sulfadiazine and silver nitrate, mafenide acetate can penetrate eschars and can be used for full-thickness burns. However, several disadvantages may limit its use. First, its lack of fungal coverage may necessitate concomitant use of topical antifungal agents. Furthermore, it may precipitate acidosis due to its anti-carbonic anhydrase activity, which may cause a hypersensitivity reaction. Finally, it is often painful to apply to partialthickness wounds, and therefore some patients may not tolerate it. Recently, triple antibiotic ointments have gained favor in general and specialty practices for outpatient management of minor burns. As an alternative to antimicrobial application, synthetic wound dressings may be applied to provide burn coverage. There are many alternatives, but superiority of one over another has not been demonstrated. Hydrocolloid dressings provide a moist environment while limiting external contamination. These coverings, such as Comfeel (Coloplast), DuoDERM (ConvaTec), and Tegasorb (3M), may be left on the wound and changed every few days. Due to their absorbent property, ease of use, and low cost of care, these dressings are a good alternative for burn coverage. Another frequently used synthetic product is Biobrane (Smith & Nephew), which is a bilaminar membrane composed of a silicone film with embedded nylon fabric into which fibrovascular tissue can grow. Compared to silver sulfadiazine, it has been shown to reduce pain medication requirements, decrease healing time, and decrease length of hospital stay. 23,24 TransCyte (Smith & Nephew) is a similar product. Other temporary and permanent skin substitutes currently available include human allograft Orthopaedic Surgery Volume 8, Part 5 15

11 (AlloDerm [LifeCell], NeoForm [Mentor Corporation]), epithelial sheets, amniotic membrane, xenograft (PriMatrix [TEI Bioscience], fetal bovine; OASIS [Healthpoint Biotherapeutics], porcine; Unite Biomatrix [Synovis Orthopedic and Wound Care], equine), dermal regeneration templates, such as the collagen-based INTEGRA (Integra LifeSciences) template, and cultured autologous grafts. Surgical Indications and Debridement Proper wound evaluation and mapping of burn depth should be carefully documented. After debridement, the initial burn diagram should be revised. When treating complex burn wounds, it is beneficial to have a wound care specialist evaluating and following the wound in conjunction with the medical team. Evaluation under anesthesia may further aid in the assessment of the tissues while minimizing patient discomfort. Superficial burns rarely require any surgical intervention, except occasional blister management as discussed above. Partial-thickness burns are difficult to manage, and much debate exists regarding surgical versus conservative management. While superficial partial-thickness burns usually heal adequately without intervention, deep partial-thickness burns are often treated with excision and grafting due to the severe scar formation that frequently occurs. Finally, it is universally accepted that full-thickness burns require operative intervention. Eschars that span the extremity and wrap circumferentially around a limb can cause vascular insufficiency. Indications for escharotomy include inadequate capillary refill, increasing pain in the setting of a full-thickness burn that is out of proportion to exam, resistance to passive extension of the fingers, and sensory changes such as numbness or paraesthesias. In obtunded, sedated, or otherwise unresponsive patients, compartment pressure measurements (>30 mm Hg) may guide the need of escharotomy. Elevated intracompartmental pressures alone in alert patients, however, should not be an indication for emergent escharotomy, and should be used to aid in the decision process when considering all other findings. Sheridan et al 25 described the principles of surgical management of eschars for diminished perfusion. Escharotomy may be performed at bedside or in the operating room. Using an electrocautery device, an escharotomy is performed by creating medial and lateral midaxial incisions through the eschar in the extremities. This releases the pressure and helps to decrease compartment tension in circumferential burns. Fasciotomy should be concomitantly considered in involved areas, especially the hand, to prevent ischemic contracture. 26 In deep partial-thickness and full-thickness burns, Janzekovic advocated early (post burn day 3 to day 5) excision and grafting. 27 Tangential excision is performed to remove necrotic and devitalized tissue. This approach preserves the deep dermal layer and the underlying subcutaneous tissues. Wounds are shaved down to viable vascularized tissue where pinpoint bleeding can be noted. This can be done with a scalpel, guarded dermatome, or Goulian knife. It is wise to set realistic goals and limits to the surgical excision as these procedures carry significant risk of losing large volumes of blood. Epinephrine may be used to help with hemostasis. When the tissues have been adequately debrided, skin grafting should be performed. Superficial granulation and underlying tissue with good vascularity provide a good foundation for skin grafts (Figure 4). Multiple graft options exist to cover tissue defects. Full-thickness skin grafts (FTSG) may be used when donor areas are readily available. However, 16 Hospital Physician Board Review Manual

12 Figure 4. Forearm after partial-thickness burn debridement and local wound treatments in preparation for skin grafting. (Image courtesy of Professor Lajos Kemeny, MD, PhD, DSc.) their use is limited by the need to close the donor sites primarily. FTSGs are less likely to contract since the entire dermis is transplanted and are advantageous to use over areas of motion, such as joints. When transplanted, FTSGs are durable, preserve some sensibility, and maintain their texture and appearance. Therefore, they are used preferentially on the face and palmar aspect of the hand. Unlike FTSGs, split-thickness skin grafts (STSG) do not involve the full layer of dermis. They are frequently used when donor sites are scarce or when large areas need to be covered. Compared to FTSGs, STSGs undergo more contraction, are less resilient, and offer poor tactile sensibility. These grafts may be used for coverage of the dorsum of the hand and for coverage of large defects. To increase coverage area, these grafts are frequently meshed in a 1.5:1 ratio. 28 Overall, the usefulness of skin grafts is limited in areas of exposed bones, joints, tendons, or neurovascular structures, and in these scenarios, muscle or fasciocutaneous flaps offer additional protection and better outcomes. Following grafting, the extremity should be immobilized in functional position to avoid development of contractures. Multiple visits to the operating room may be required to completely close a wound. Additional devices, such as vacuumassisted therapy, may be utilized as well. Orthopaedic Considerations In orthopaedic practice, the skeletal effects of burns may present challenging scenarios. Orthopaedic Surgery Volume 8, Part 5 17

13 Although the mechanism of bone metabolism is incompletely understood, it is not surprising that thermal injuries have effects on bone growth and development. Rutan and Herndon 29 have shown that there is a linear growth retardation of children following severe burns; however, with time, the growth rate returns to normal, creating a fixed limb length deformity. When burns involve skin over joints, the scarring and contraction of the tissues may progress to deformity and contractures. When skin grafting is required, FTSGs should be used for these areas to minimize the contracture that occurs. In patients with concomitant fractures and thermal injuries, careful consideration should be given to the soft tissue status of the patient and treatment goals. Often, early skeletal stabilization outweighs the increased risk of infection in patients with burns. 30 In children, open reduction and internal fixation within 48 hours after thermal injury has shown promising outcomes with high union rates. 31 Hand injuries present a unique challenge in orthopaedic practice. Given that we constantly use our hands to interact with the external environment, burns often affect the upper extremity. Up to 8% of upper extremity complaints that are seen in the emergency room are due to thermal injury. 32 Because of the high demands we place on our hands and the intricate anatomy, even subtotal burn injuries of the hand can lead to severe deformity and disability. Specifically, thermal damage can lead to shortening of the collateral ligaments and intrinsic tendons. At its worst, this will lead to claw deformity. In order to prevent this deformity, splinting and early rehabilitation should be instituted as soon as wounds allow. When a palmar hand defect requires skin grafting, FTSGs provide less risk of contracture formation and increased sensibility. STSGs provide the best option for dorsal areas of the hand. As a substitute, skin alternatives may be used. This is especially useful for patients whose burns are extensive (>40% TBSA). When bone or joint coverage is required, local flaps may be beneficial if donor sites are available. Other sequelae of thermal injuries are heterotopic ossification and periarticular contractures, which frequently restrict motion of the affected joints. If patient disability is significant and functional limitations exist, surgical release of contractures and possible skin grafting or reconstruction may be undertaken. Symptomatic heterotopic ossification, although rare, may necessitate excision. Rehabilitation The goals of rehabilitation are to preserve motion and to prevent contracture formation. These goals are usually achieved via a multispecialty approach. Initially, occupational and physical therapists will focus on splinting and early motion protocols, but various modalities can be used to supplement rehabilitation. Specialized baths and hydrotherapy can aid in wound care. Specific dressing and splinting techniques can aid in edema control. Desensitization is helpful in treating chronic pain. Finally, psychological evaluation and treatment is often necessary to counteract symptoms secondary to the disfiguring nature of serious thermal injuries. 33 Freezing Injuries Frostbite injuries, which most commonly involve acral structures, such as fingers, toes, ears, and nose, classically result from prolonged exposure to subfreezing temperatures. Freezing insults to the extremities are common in cold climates and during winter recreational activities. However, tissue 18 Hospital Physician Board Review Manual

14 damage may even ensue from seemingly benign exposures, such as the use of cooling devices or gel packs. With the wide acceptance of the R.I.C.E. (rest, ice, compress, and elevate) protocol for musculoskeletal injuries, iatrogenic frostbite has been reported Recently, a study determined that frostbite injury may occur with finger contact of highly conductive materials (conductivity close to metals) in as quickly as 3 seconds at the temperatures of a conventional freezer ( 15 C or 2 F). 38 Pathophysiology Thermal injuries due to cold exposure have long been compared to burn injuries. In fact, the mechanism and the presentation of tissue injury is similar. However, there are great differences due to the temporal relationship and the anesthetic effects of cold exposure. Unlike burns, cold injuries usually require a prolonged exposure to the subfreezing environment. This provides the exposed person a chance to alter his or her contact with the environment by adding protective barriers or by escaping the insult. Certain circumstances may prevent this protective response, such as entrapment in a cold environment due to concurrent injuries, intoxication, or psychiatric conditions. On the other hand, the slow onset of frostbite may be ignored due to analgesia of the involved areas, which disables the conscious protective response to remove the offending agent or escape the environment. It is well documented that cooling therapy has analgesic effects locally and centrally, which increase the pain threshold Cryotherapy may create a dangerous scenario where the analgesia locally leads to the inability to feel the pain associated with permanent nerve damage. Cold temperatures lead to microscopic alterations of cell physiology that produce the clinical picture of frostbite. Decreasing temperatures cause vasoconstriction and increased blood viscosity, which in turn decreases tissue perfusion and subsequent oxygenation. This procoagulable environment can lead to the formation of thrombi in small vessels. Furthermore, spreading inflammation, vascular stasis, and thromboses lead to local ischemia on the cellular level. Extracellular water plays a central role in this tissue destruction with the formation of ice crystals. In addition to macroscopic mechanical destruction, ice crystal formation leads to water shifts outside of cells, which causes dehydration and cell death that progresses to necrosis of the affected tissue bed. 42 Understanding the microscopic pathology of freezing has helped guide the development of treatment principles of these injuries. Diagnosis The proper evaluation of a cold-induced injury requires a detailed history and physical examination with particular attention to the neurovascular status of the affected extremities. Frequent reexamination is essential in following the evolving clinical picture of these types of injuries. Evaluation of the freezing wound is diagnostic and prognostic. It also aids in guiding proper treatment. The system used for classifying cold injuries according to severity is similar to the system for burns. McAdams at al 43 explored the commonly used 4-stage classification in degrees and refined it in terms of depth of tissue injury (Table 4). First-degree and second-degree frostbite are categorized as superficial insults (Figure 5). These injuries demonstrate local effects that are limited to the skin, with advanced forms causing blisters that later desquamate and form an eschar. Thirddegree and fourth-degree frostbite involve the subcutaneous tissues and other deep tissues, respectively (Figure 5B). These stages present Orthopaedic Surgery Volume 8, Part 5 19

15 Table 4. Classification of Freezing Injury Classification Depth Characteristics Superficial Deep First degree Superficial skin involvement Edema, erythema Second degree Full-thickness skin involvement Blistering, desquamation Third degree Involves subcutaneous tissue Blue-gray discoloration, hemorrhagic blisters Fourth degree Deep tissue involvement Deep necrosis to muscle, tendon, bone with hemorrhagic blisters, necrosis and eventually, mummified black tissues. Advanced imaging techniques such as bone scans (technetium-99m), magnetic resonance imaging, and laser Doppler flowmetry have been used in clinical practice to further aid in the assessment, staging, and treatment of these injuries. However, these methods have not been validated to conclusively delineate the proper intervention. 28 Management Well-established guidelines have been developed for the treatment of these types of injuries. The initial step is to remove the victim from the cold exposure or the offending cold source. In clinical practice, this step has usually already been undertaken. Subsequently, the next step in the management of freezing injuries is rewarming. The body s core temperature has to be elevated and the affected extremity warmed. Rapid rewarming of the frostbitten region can be achieved by using 40 C to 42 C water baths for 15 to 30 minutes until the target temperature is achieved. If vascular compromise is noted without any structural constriction, sympathetic blockade or antithrombotic therapy may be indicated. Bruen and colleagues demonstrated that intra-arterial tissue plasminogen activator (tpa) will decrease the rate of post-freezing amputation when administered within 24 hours of exposure. 44 However, this recommendation is controversial, especially when wounds involve localized areas in extremities that have otherwise intact vascular status. The standard protocol for treating frostbite injuries has been described by Su et al 45 based on McCauley s initial guide of management. The authors recommend careful monitoring if the tissue involvement is superficial. However, according to their treatment algorithm, deep tissue involvement warrants further investigation and possible surgical intervention. They advocate the use of a triple-phase bone scan at 48 hours and at 5 days. The purpose is to delineate blood flow and viable areas, which would aid in debridement efforts. Some debate has surrounded the utility of bone scans, and their clinical use has been questioned. 46 The management of blisters has been a topic of long-standing debate. It is thought that their contents are similar in composition to those seen in burns (high in prostaglandins and thromboxanes) and may predispose surrounding tissues to ischemia and vasoconstrictive effects. 47 Most physicians believe that blisters should be left alone unless they are ruptured, tight, or infected. 48 However, others advocate opening clear vesicles and draining hemorrhagic ones to eliminate the potentially damaging effect of the fluid contents. 46 When tense blisters compromise the vascular 20 Hospital Physician Board Review Manual

16 status of the affected extremity, as in the case of a constriction syndrome, urgent decompression of the bullae is advocated. Topical antimicrobial ointments and dressings may be applied according to burn wound management principles. Aloe vera 49 or silver sulfadiazine may be used for their antimicrobial and antifungal properties as an adjunct. Early motion and physical therapy should be started as soon as the wounds allow. Complications and long-term disability In children, long-term complications have been reported due to the immature physiology of the affected areas. When freezing injuries occur near open growth plates, growth retardation and physeal arrest may occur, as described by Bigelow and Ritchie. 50 Frostbite has also been implicated in early arthritis in children with a history of such wounds. 51 In the presence of circumferential confluent blisters, a constriction syndrome may ensue where first vascular and then ischemic changes lead to irreversible tissue damage. In these cases, the external circumferential constraint functions like a tourniquet, which may lead to insufficient blood flow to the distal structures. This requires immediate surgical release in order to prevent necrosis and neurological dysfunction. Although constriction syndrome and compartment syndrome may cause similar pathology and have similar mechanisms, constriction syndrome implies an external agent that impedes circulation to reach distal parts of the extremity. With timely release of the constriction, distal blood supply can be returned to the affected areas without the need for fasciotomy. Long-term disability from frostbite may include cold intolerance and hyperhidrosis in the affected extremity. Occasionally, frostbite-induced Raynaud s phenomenon may develop in these patients. A B Figure 5. Frostbite injuries. (A) Superficial frostbite with blister formation (second degree). (B) Deep freezing injury. (Images courtesy of Professor Lajos Kemeny, MD, PhD, DSc.) Electrical Injury In contrast to burns and freezing injuries, electrical injuries occur mostly in industrial settings. 1 Although minor electrical contact does not create burns, high-energy exposure can cause fullthickness burns and major medical complications. When evaluating these types of injuries, all areas of contact have to be assessed. In addition to the Orthopaedic Surgery Volume 8, Part 5 21

17 A B entry wound, which is usually the contact point between the electric source and the skin, the exit wound has to be identified and examined. As may be expected, the hand is affected in up to 90% of all electrical injuries (Figure 6). 52 However, it is important to keep in mind that arcing may occur and that the current may exit and reenter the body (Figure 6B). Pathophysiology Current follows the path of least electrical resistance. As tissues have variable constituents, the flow of charge will select a path through tissues that is more accommodating to the passage of electrons. Nerves and tissues with high water and electrolyte content conduct electricity well. On the other end of the spectrum, bones have high resistance and serve as relative insulators. The flow of electrons creates current. The magnitude of current determines the tissue damage (amount of heat that is generated given the resistance of a particular tissue or material). Voltage is the potential difference and determines if the current enters the body or not. Ohm s law relates the potential difference measured in volts (V) to resistance (R, unit: Ω) and current (I, unit: amp): I = V R Figure 6. Electrical burn injuries. (A) High-voltage electric injury. (B) Lightning injury. (Images courtesy of Professor Lajos Kemeny, MD, PhD, DSc.) The severity of the burn relates to the magnitude of the current, the type of current (direct or alternating), the duration of contact, and the path that the electricity takes. Thermal injuries may be caused by the electric current or the electric arc. Alternating current is generally more dangerous with greater morbidity and mortality because alternating current creates tonic muscle contractions, which often make it difficult for victims to let 22 Hospital Physician Board Review Manual

18 go of the electric source and further propagates the tissue damage. 53 Current over 16 to 20 ma is the threshold for tetany. Furthermore, alternating current has the propensity to lead to cardiac arrhythmias and pulseless electrical activity, especially when the frequency is in the 40- to 60-Hz range. 54 Electrical injuries are categorized as high-voltage, low-voltage, and lightning injuries. High-voltage is defined as over 1000 V, while low-voltage is defined as under 1000 V. High-voltage may produce a wide variety of systemic complications including cardiovascular (eg, arrhythmias, asystole), pulmonary (eg, respiratory distress, diaphragm paralysis), neurologic (eg, seizure, chronic pain), and renal (eg, electrolyte imbalances, rhabdomyolysis, acute tubular necrosis) manifestations. From an orthopaedic standpoint, tetany can cause fractures, dislocations, tendon injuries, and muscle damage. Bone lesions may be created by the current due to periosteal necrosis and melting of the calcium phosphate matrix in high-energy insults. 54 These lesions require a long time to heal and occasionally may get infected or create sinuses. Management Electrical burns that are seen in the emergency room need rapid evaluation and patienttailored treatment. After the patient is stabilized, evaluation of electrolyte balance with lab work and evaluation of cardiac function by electrocardiogram should be performed. When electricity creates enough damage to cause a burn, 18% of patients require wound debridement and 10% need skin grafting. 1 Due to the severity of the thermal injury and the tissue damage associated with electrical injuries, urgent escharotomies are often required. Benign-appearing entry and exit wounds may conceal full-thickness burns underneath that are more extensive than they appear superficially. Therefore, any patient with a burn from an electrical injury should be evaluated at a burn center. Immediate or early debridement should be performed as soon as the patient can medically tolerate it. A second debridement and evaluation should be undertaken 48 hours after the initial operation. This will help clarify the extent of the injury and the viability of the tissues. Further operations may be necessary until the wounds are stable and the damage has evolved. At this stage, flap coverage and tissue reconstruction may begin. Wound care should follow general burn principles as outlined in the above sections. Chemical Burns Chemical burns are less common than other burn types, accounting for 3.4% of all burn injuries (Figure 7). 1 Chemical burns present a diagnostic and management challenge. Often, the chemical agent responsible for the injury and its specific formulation is unknown. Even when the involved agent is known, the clinical presentation may be variable. Furthermore, since there is a vast number of agents that cause skin irritation and burns, experienced clinicians may be misled by these types of injuries. Another characteristic of these insults that is different from thermal injuries is the continuing tissue damage until the chemical is removed from the skin. If proper decontamination procedures have not been initiated, this may be the case even when the patient is in the health care setting. This fact creates a risk for health care workers that come in contact with the patient during the initial encounter. Orthopaedic Surgery Volume 8, Part 5 23

19 Figure 7. Chemical burn of the forearm. (Image courtesy of Professor Lajos Kemeny, MD, PhD, DSc.) Pathophysiology Chemicals that have a ph less than 7.0 are acidic. Strong acids (ph <2.0), such as hydrochloric acid, may damage the skin and other tissues. The mechanism of the chemical reaction is release of hydrogen ions, which causes molecular changes leading to tissue damage by coagulation necrosis due to denaturation of proteins. This reaction continues until the tissue neutralizes the acid or a neutralizing agent is added. Bases or alkaline solvents are chemicals that have a ph greater than 7.0. Because of the body s limited capacity to buffer strong bases, these substances often cause serious tissue destruction, forming fatty soaps by liquefaction necrosis. Some substances (ie, cement or lime-alkaline solvent) cause anesthesia of the skin, which delays treatment. Management The first priority of chemical injury management is decontamination. By removing the offending agent from the skin, the chemical reaction is minimized. Dry chemicals and powders should first be brushed off the skin with careful attention not to spread the offending agent to uninvolved areas. With a few exceptions, water dilution should start immediately and continue for 20 to 30 minutes. Alkali burns require prolonged dilution, often in excess of 1 to 2 hours. Neutralizing agents should generally be avoided as thermal damage from neutralization as well as direct damage by the treating agent may occur. Specific treatments of commonly encountered chemical burns are listed in Table 5. When exposure is minor, topical antibiotics may be applied and local wound care should be 24 Hospital Physician Board Review Manual