Surgical Treatment of Thermal Injuries of the Upper Extremity

DEFINITION

Thermal injuries of the upper extremity include contact, scald, flame, chemical and electrical burns, and present with both acute and chronic injury that may require surgical intervention.
Despite aggressive acute care, splinting, and therapy, long-term hand and wrist deformities due to burn injuries are common.
Following burn injuries, scar contractures are common due to the loss of normal skin pliability, which often require surgical release.

ANATOMY

Burns yield both a local and systemic response.
Locally, there are three zones of injury.
- The zone of coagulation describes the point of maximum damage with irreversible tissue loss.
- The zone of stasis represents the area of diminished tissue perfusion and is most critical, as it represents the zone of reversible injury with adequate resuscitation and wound care.
- The zone of hyperemia is most peripheral and typically represents tissue that will recover in the absence of overwhelming infection or hypoperfusion (FIG 1).

PATHOGENESIS

Systemically, burn injuries result in the release of inflammatory mediators that can cause widespread physiologic changes for those injuries that are more than 30% of the total body surface area. For example, cardiovascular collapse can occur from increased capillary permeability and diminished myocardial contractility.
Inhalational injury can result in bronchospasm and acute respiratory distress syndrome. A catabolic state results from an increase in metabolism greater than three times the basal rate. Finally, patients may be relatively immunocompromised from downregulation of the immune response.

FIG 1 • Burn zones of injury.
Electrical shock produces a complex pattern of injury in which the severity of injury depends on the intensity of the current and duration of contact.
- Electric current travels through the body, creating “entry” and “exit” points, damaging any tissue in between these two points.
- As the electrical current travels, heat is generated along its path, leading to thermal damage. The amount of heat generated (and tissue damage) is proportional to the voltage of the current as well as the resistance of the tissue.
- Alternating currents can interfere with the cardiac cycle, increasing the risk of arrhythmias.
- Electrical burns are classified as high voltage (≥1000 V) and low voltage (<1000 V).
- Electrical injuries often extend far beyond the visible cutaneous burn and involve deeper structures.
- Tissues with high electrical resistance, such as the skin and bone, generate more heat, causing more damage to both themselves and the surrounding tissues. Therefore, patients with high-voltage electrical burns often sustain extensive deep tissue and muscle injuries that predispose to developing acute compartment syndrome.
Despite splinting, range-of-motion exercises, compression, and positioning, 80% of patients will have decreased joint motion and up to 10% have difficulties with activities of daily living.
Increased and disorganized deposition of collagen fibers following burn injuries results in compact, foreshortened scars. The amount and severity of hypertrophic scarring and contracture is directly related to the depth of the burn and the time required for wound healing.

NATURAL HISTORY

Superficial burn injuries involve only the epidermis.
Partial-thickness burns involve the entire epidermis and varying levels of the dermis and dermal appendages.
Full-thickness burns injure all layers of the epidermis and dermis and can extend to deeper structures.
Superficial burns are painful and involve only the epidermis, which is erythematous and blanches with pressure. These burns will heal with minimal or no scarring and can be managed with local wound care.
Partial-thickness burn injuries involve the epidermis as well as varying degrees of the dermis. These can be considered as either superficial or deep, depending on the degree of injury to the dermis. Superficial partial-thickness burns are typically sensate, moist, weepy, and painful after sloughing of the epidermis and usually heal within 2 weeks of injury. Deep partial-thickness burns extend into the reticular dermis
and typically heal within 3 to 8 weeks and often require excision and grafting (FIG 2).
Full-thickness burns involve the entire thickness of the skin and are characterized by charred, painless, leathery skin with visible coagulated vessels.

PATIENT HISTORY AND PHYSICAL FINDINGS

Assessment of the Burned Patient

In addition to routine medical history, it is imperative to obtain the mechanism of burn injury and assess for other concomitant injuries.
- High-voltage electrical burns, burns that occurred in an enclosed space, or burns from explosions require trauma and critical care to evaluate and treat other potential lifethreatening injuries.
Physical examination should focus on determining the extent of burn injury and vascular status.
All upper extremities should be assessed for signs of vascular compromise, such as diminished pulses, poor capillary refill, cool skin temperature, and poor turgor.
- Vascular insufficiency is uncommon with superficial and partial-thickness burns. Patients with crush injuries, full-thickness burns, circumferential injuries, and those in association with lacerations or other trauma may be at risk for vascular insufficiency.

Classification of Burn Injuries

Superficial burn injuries involve only the epidermis. Partial-thickness burns involve the entire epidermis and varying levels of the dermis and dermal appendages. Full-thickness burns injure all layers of the epidermis and dermis and can extend to deeper structures.
- Superficial burns are painful and involve only the epidermis and are erythematous that blanch with pressure. These burns will heal with minimal or no scarring and can be managed with local wound care.
Partial-thickness burn injuries involve the epidermis as well as varying degrees of the dermis. Partial-thickness burns can be considered as either superficial or deep partial thickness, depending on the degree of injury to the dermis.
- Superficial partial-thickness burns are typically sensate, moist, weepy, and painful after sloughing of the epidermis and usually heal within 2 weeks of injury.
- Deep partial-thickness burns extend into the reticular dermis and typically heal within 3 to 8 weeks, often requiring excision and grafting.
Full-thickness burns involve the entire thickness of the skin and are characterized by charred, painless, leathery skin with visible coagulated vessels.

FIG 2 • Upper extremity burn injury demonstrating superficial, partial-thickness, and full-thickness burns.

Compartment Syndrome

Compartment syndrome may result from burn injuries, especially electrical burn injuries.
Acute circumferential or near-circumferential full-thickness burns of the extremity may compromise distal perfusion and require escharotomy, in which the unyielding burned tissue is released or excised.
- The inelastic skin in a circumferential burn acts as a tourniquet, which compromises venous return and capillary perfusion leading to tissue ischemia distal to the burn.
The differential diagnosis for compartment syndrome includes nerve injuries causing paresthesias and arterial or venous insufficiency from other causes (eg, trauma).
Compartment pressures can be measured with a commercially available pressure transducer or by creating one using an 18- or 20-gauge needle, a syringe containing saline, a pressure transducer, and a three-way stopcock.
Treatment for compartment syndrome of the forearm and hand should be initiated based on clinical suspicion. Prompt fasciotomy minimizes functional loss and promotes recovery. Fasciotomy should be performed if compartment pressures are higher than 30 mm Hg for normotensive patients or within 20 mm Hg of the diastolic pressure for hypotensive patients.

IMAGING AND OTHER DIAGNOSTIC STUDIES

In addition to routine medical history, the mechanism of burn injury and assessment for concomitant injuries is sought. High-voltage electrical burns, burns that occurred in an enclosed space, or burns associated with explosions and inhalation injury require further consultation.
Plain radiographs are obtained if hand reconstruction for scar contractures is planned to assess for heterotopic ossification or arthritic changes that may require additional treatment, such as capsulotomy and ligamentous releases.

NONOPERATIVE MANAGEMENT

Acute superficial or partial-thickness burns over noncritically functioning areas that are expected to heal within 2 to 3 weeks may be managed with dressing changes. Typical options for topical wound care are detailed in Table 1.
- Topical antibiotic agents (eg, Bacitracin, Silvadene, Sulfamylon, Mepilex Ag, Acticoat) are applied and changed regularly as the burn heals.
- Empiric systemic antibiotics are not indicated for burn injuries.
- Burns should be cleaned with soap and water daily and covered with topical antimicrobial agents.
- For early, immature scarring within 6 months of injury, conservative measures can dramatically improve scar appearance through collagen remodeling.
  - Examples include pressure garments, silicone gel/sheeting, and physical therapy. All have been shown to control hypertrophic scarring with full-time use over several months.

Table 1 Topical Agents and Dressings for Burn Treatment

	Description	Application	Pros	Cons
Acticoat	Silver-coated polyethylene net dressing	Change every 3-7 d	Few dressing changes, painless, large antimicrobial spectrum	Cost
Adaptic	Impregnated mesh	Once daily	Painless, nonadherent, good moisture	No antimicrobial effect, may dry out
Aquacel Ag	Silver rayon mesh dressing	Change every 1-14 d	Painless, large antimicrobial spectrum	Difficult patient maintenance
Bacitracin	Topical agent	1-4 times daily	Painless, inexpensive, uncommon incidence of bacterial resistance	Antibiotic resistance and dermatitis with long-term use
Silvadene (silver sulfadiazine)	Topical agent	1-2 times daily	Painless, cooling effect; fight gram-negative bacteria	Poor deep eschar penetration, daily dressing changes, leukopenia
Mepilex Ag	Silver-impregnated foam dressing	Every few days	Ease of application and excellent patient tolerance	Requires clean, noncontaminated wound bed; not effective for full-thickness injury
Sulfamylon (mafenide acetate)	Topical agent	Daily	Bacteriostatic action	Application may be painful.
Xeroform	Impregnated mesh	Once daily	Nonadherent, bacteriostatic activity	Dessication