Components of both an arc burn and a contact burn make up the mechanism of injury. Arc burns result from electrolyte-containing saliva ( the small pool of drool at the corner of the mouth or the moist mucosa lining of the mouth) bridging the polarity gap of the wires and causing an arc or flash. The contact component of the burn occurs as the current passes from the electrical source through the mouth and to the ground through the path of least resistance.
The tissue injury results from direct thermal changes at the entrance and exit site. Temperatures can reach as high as 3000°C (5400°F). Alternating current at low voltage is more dangerous than direct current. Alternating current produces tetanic spasm and can freeze the patient to the power source with subsequent prolongation of contact. Nerve, blood vessels, and muscle offer little resistance and show the greatest destruction. Tendon, fat and bone tissue have highest resistance and show less destruction. Photo credit
The burn most often invades both upper and lower lip and the oral commissure. There is usually a significant tissue defect in this area. They are usually full thickness burns involving muscle destruction. The extent of tissue necrosis is not immediately known as it may progress for some time after injury. Patient observation reveals that these wounds are usually not as painful as they appear. Tetanus prophylaxis must be verified and boosters given if indicated.
Immediately after injury, the wound margins appear coagulated without an apparent margin of necrosis. Blood vessels are cauterized by the heat, so little or no bleeding is present. At approximately six hours, the wound is covered with whitish fibrin, a surrounding rim of erythema, and edema of the local tissue. The edema has a tendency to increase, as well as a progressive thrombosis, so after 24 hours there is usually a significant margin indicating the area of tissue necrosis. Bleeding from the labial artery has been reported to occur from these wounds between 1 and 2 weeks after injury as the eschar sloughs. The healing process follows the formation of the eschar, and takes 1 to 2 weeks. At that time, the eschar will slough from the wound, leaving a scar that has a tendency to contract.
The treatment concept
Surgical intervention immediately after injury is not indicated, because the extent of tissue necrosis cannot be defined precisely. For this reason the initial treatment is conservative. Topical antibiotic ointment should be used to prevent infection and assure wound healing. Some of the more severely injured patients were also treated with oral penicillin. Reconstructive procedures were planned after the healing was completed and after the degree of functional and/or aesthetic deformity was established (usually 6 months post-injury).
Attention must be paid not only to the existing deformity, but also to the functional impairment. After the healing process, the size of the tissue defect is most often substantially decreased because of scar contracture. The oral commissure is often narrowed and shortened, causing functional impairment and aesthetic deformity. Sometimes functional impairment and deformity is evident only during movement of the lips and cheeks (smiling or opening the mouth). Defects of the vermilion in the area of the commissure and adjacent upper and lower lips present a difficult reconstructive problem. However, it is more difficult to correct functional impairment and obtain perfect symmetry during movements. Both form and function must be considered when planning a reconstructive procedure.
During the six months post-injury, special attention should be paid to the scar formed in the area of the commissure. Vigorous scar massage should be done using vitamin E cream, kenalog cream, or Mederma to soften the scar as much as possible. Massage is performed by the patient (or parent for the child) five to seven times per day, for 2 to 3 minutes each time. Some suggest the use of splints to prevent contracture of the commissure. photo credit
Planning of the reconstructive procedure depends on the size, shape, and location of the defect, as well as the texture of the scar and the condition of the surrounding tissue. The surgeon must determine which design and which tissue to include into the local flap reconstructive procedure. The reconstructive procedure for recreating the commissure may be combined with that for reconstructing the vermilion on one or both lips adjacent to the commissure. Staged procedures are required in cases where defects of the vermilion are substantial. In these cases, the commissure is reconstructed first, followed by reconstruction of the lip 6 to 12 months later.
Reconstruction of the oral commissure, when performed simultaneously with reconstruction of the adjacent vermilion of the upper and/or lower lip, is based on recruiting a mucosal flap from the cheek and transferring it to the commissure and the adjacent lip defects that require reconstruction of the vermilion. The operation starts with precise measurements to determine the position of the commissure after reconstruction and anticipates postoperative scar contracture. The length of the oral fissure on the affected side is determined according to the measurements taken on the normal side. The commissure on the affected side is extended an additional 2 mm laterally to allow for postoperative scar contracture, which will narrow the commissure, bringing it up to the length of the normal side. It is also essential to position the commissure exactly at the same level as on the normal side. The incision is usually carried through the skin and muscle to completely remove the scar and to save the intact mucosa adjacent to the commissure. The design of the mucosal pedicle flap may vary, depending on how much tissue is necessary for reconstruction of the vermilion and closure of the lip defects. (photo from third reference article).
- Burns, Electrical by Richard F Edlich, MD PhD--eMedicine Article
- Electric Burns of the Lip--Pediatric Dentistry, "just for kids"
- Oral Commissure Burns in Children; Plastic & Reconstructive Surgery. 97(4):738-744, April 1996; Canady, John W. M.D.; Thompson, Sue Ann Ph.D.; Bardach, Janusz M.D.
- Bardach, J. Local Flaps and Free Skin Grafts in Head and Neck Reconstruction. St. Louis: Mosby, 1992.
- Safe Uses of Extension Cords
- Reducing the Risk of Burns--Cincinnati Children's Hospital