HAND BURNS

Burns to the hand are common. Most are small and confined to the upper limb but some are part of a major burn. Although the hand comprises a small surface area, management of a hand burn assumes a high priority because of its functional importance. The majority of hand burns can and are managed without complication in Accident Departments and General Practitioner Surgeries. A minority, however, need early Specialist intervention.

The depth of a burn is simply divided in partial thickness and full thickness. Partial thickness burns have the capacity to heal rapidly because of the presence of viable dermal components. Re-epithelialization occurs from both the base and the edge of the burn-wound and healing should be complete within 21 days. Full thickness burns only heal from the edge and therefore healing is slow in anything but the smallest burns. Delayed healing results in a poor quality contracted scar which, in the hand, inevitably compromises function.

First-Aid

Tissue damage can continue after injury because of retention of heat in clothes and tissues or if chemical agents remain in contact with the skin. Wet or contaminated clothes should be removed and burned areas should be cooled/lavaged with running water. The exceptions are lime burns (cement) in which all powder should be brushed off prior to lavage, and elemental sodium or potassium which ignite on contact with water. Cooling need not exceed 10 minutes, particularly in children in whom hypothermia may follow over-enthusiastic cooling. The burned hand can be covered by a clean dry cloth or Cling-film prior to seeking medical aid.

Assessment

The assessment of burns can be difficult for even experienced clinicians. Knowledge of the burning agent provides a valuable clue. It is recognised that exposure to flames or electrical current almost always results in a full thickness burn whereas a scald with water usually produces a partial thickness burn. However, if the scalding fluid is fat, the burn is almost certainly full-thickness.

The severity of a burn is proportional to both the intensity of the burning agent and the duration of its contact. Try to ascertain the temperature of scalding fluids, the voltage and type of electrical current and the concentration of chemical agents. Although obtaining a clear history can be difficult, the information can often be obtained with careful questioning. "How long before had the kettle boiled"? "Did the tea have milk in it"? "Did your clothes catch fire"? Electrical contact burns caused by alternating currents are often more serious because muscle tetany prevents release of the live terminal.

The effects of a burning agent can be limited by prompt first-aid. Failure either to remove gloves or mittens soaked in hot fluids or to apply cold water quickly to scalding or chemical burns may lead one to suspect that burn is deep.

The depth of a burn is judged on its appearance, texture and sensitivity. It can be difficult to distinguish between erythema and superficial partial thickness burns particularly if the patient is seen soon after injury when blister formation is minimal. Partial thickness burns can be identified if the skin is rubbed firmly, causing separation at the dermo-epidermal junction (Nikolski sign). The presence of thrombosed capillaries in burned skin is pathognomic of a full thickness burn. Flash burns whether electrical or from vapour are usually very superficial but are often mistaken as deep burns because of the presence of carbon-staining. For this reason, it is helpful to clean the burned area prior to examination.
Sensory testing is difficult under any circumstances. Pin-prick testing is often unnecessary and is inappropriate in children. If performed, it is preferable initially to stroke gently the burned area with a sterile needle, having familiarised the patient with the test on an unburned area.
Accurate assessment burn-depth is particularly difficult in the early hours after injury. Re-examination after 24 hours may be useful as the signs are well established by this time allowing definitive decisions to be made about management.

The likely depth of burn also depends on the area burned because the thickness of skin of the hand varies considerably. The thin dorsal skin is much more vulnerable than the palm. The early appearance of swelling and immobility in a burned hand is worrying and indicates that the burn is potentially serious and that the depth may have been underestimated.
Partial thickness burns can be arbitrarily divided into superficial and deep by experienced clinicians according to the subtleties of the clinical presentation. The more superficial injuries can be expected to heal in 5 to 10 days, deeper burns in 11 to 21 days.

It is important to identify patients who require early intervention and/or referral to a Plastic Surgery Service. If you have any doubt, ring your Regional Burns Unit for advice.

It is mandatory to check the circulation distal to any burn. The recognition of circulatory embarrassment must be followed by urgent and appropriate treatment. Failure to do so can result in loss of function, loss of limb or loss of life due to rhabdomyolysis. If rapid transfer to a specialist unit cannot occur then treatment should be undertaken by a senior member of the resident surgical staff. High voltage injuries need early specialist intervention and most Plastic Surgery Units will provide staff to assist with the early management of these patients on site.

Conservative management

The burned area should be cleaned gently with a soapy solution such as Savlon, washed off with saline. Blisters that have burst, or about to, should be debrided, all loose epidermis being removed. Intact blisters should be left alone as they are comfortable and they provide a sterile environment for healing to occur. Aspiration confers no advantage and can introduce infection into a closed area. The exceptions are either blisters that are impeding digital motion or those caused by chemical burns, in which permeation of the burning agent into the blister fluid may occur. Bitumen burns are common and often cause deep burns which require surgery. Its removal is difficult but is best achieved with a combination of Swarfega and liquid paraffin.

If it is judged that a burn is superficial and that it will heal within one week, suitable non-adherent dressings include Tulle-Gras, Silicone NA or Tegapore covered by absorbent gauze. Fingers are best dressed individually using tubigauze or with composite dressings such as Adaptic. Unburned fingers should be left free allowing full motion. Complex burns involving multiple fingers, web spaces and parts of the palm are best managed in a clean polythene bag or glove. This can be applied dry as it will soon fill with serum. This allows far more digital movement whilst healing occurs. This is far simpler approach than other dressings, having the advantages of comfort, speed and the ability to observe the hand. The hand always becomes macerated but although this is somewhat unsightly it is of no significance. Semi-permeable bags which include sections of Goretex reduce the amount of maceration but they are not widely available.

Burns become heavily colonised by bacteria within 5 days of injury. If it anticipated that healing will take longer than a week then a topical antiseptic be used to limit the extent of colonisation. A burn-wound is dynamic and infection can convert it from partial thickness to full thickness. Silver sulphasalazine (Flamazine) is the most widely used agent and this can be easily added to a dressing or placed in the polythene bag. It should be noted that these agents are effective for a limited time and that dressings should be changed daily if they are to be effective anti-microbiological agents. Regular wound swabs should be taken during treatment. There is however no place for the prophylactic administration of antibiotics or treating swab results. Their use should be reserved for clinical infection as indicated by cellulitis and pyrexia.

Prevention of swelling and preservation of motion are crucial to the long-term outcome. A burned hand should be kept elevated and movement encouraged. Physiotherapy is mandatory for all but the most trivial burns as stiffness can occur rapidly, particularly at the proximal interphalangeal joint. Nocturnal splinting is useful to maintain the hand in the "position of function" which has least tendency towards joint contracture.

Burns, which are of significant size, that have not healed within three weeks should be referred for a specialist opinion. Healing is likely to be prolonged and accompanied by significant contracture. The scars will be of poor quality, being prone to frequent breakdown after minor trauma and exposure to a multitude of household chemicals and food-stuffs.

Surgical management

Escharotomy is often performed poorly, there being either a failure to release the full length of the burn or poor planning of incisions with damage to nerves or exposure of structures. Incisions on fingers should be mid-axial to avoid subsequent loss of motion due to contracture. These need not be along both sides of a finger and ideally should avoid vulnerable surfaces such as the ulnar border of the hand. Incisions on the hand should be planned carefully without going straight across natural creases but avoiding narrow skin flaps.

Excision of a burn is indicated when a burn is deep or if a burn has failed to heal after three weeks of conservative management. Full thickness burns are sharply excised with a scalpel whereas areas of intermediate or mixed depth are sequentially shaved with a skin graft knife until viable tissue is reached. Excision should be done under tourniquet control. Experience is required to gauge tissue viability, the key indicator being fixed-staining of tissues which is indicative of necrosis. Release of the tourniquet can confirm the adequacy of the excision, should there be any doubt.

The split skin graft (SSG) is the work-horse of burn reconstruction. It has the advantages of easy harvest, no donor defect and reliable "take". It, however, is thin and fails to prevent wound contraction. Although SSG is suitable for use on the dorsum of the hand, it is not acceptable in the palm or web spaces where contracture leads to long-term functional problems. Full thickness grafts is to be preferred in these sites, being associated with less contracture formation and providing more robust skin, more suited to the hand. Grafts are not suitable if there are deep tissues, such as tendon and nerve are exposed. These structures should be covered by a vascularized flap. This can be obtained locally (e.g. cross-finger, metacarpal artery island flaps), regionally (e.g. reverse radial artery or posterior interosseous flaps), distantly (e.g. groin or cross-arm flaps) or using microvascular techniques (e.g. lateral arm or groin flaps).

Special burns

Electrical burns are notoriously difficult to assess as there is usually considerably more deep damage than is evident to external inspection. High voltage injuries cause direct damage to blood vessels and muscle necrosis with the rapid onset of compartment syndromes. Involvement in the hand may result in swelling in multiple compartments. Fasciotomy needs to include decompression of the median and ulnar nerves, release of palmar spaces including the intrinsic muscles.
The mainstay of management of high voltage injuries is aggressive debridement of all necrotic tissues. This may include damaged vessels and immediate reconstruction of these should be undertaken if the limb is considered salvageable. It is difficult to judge the extent of skin and muscle necrosis at the first operation and it is better to delay skin cover until a second procedure. Vulnerable deep structures such as exposed vessel grafts can be satisfactorily covered by a split skin graft which acts as a biological dressing.

Hydrofluoric acid is widely used as a metal or glass cleaning agent. It readily penetrates skin and causes burns that are extremely painful and which have a predilection for the nail-bed which lacks a stratum corneum. Hydrogen ions cause a characteristic coagulated acid burn. Fluoride ions cause progressive tissue necrosis and decalcification of bone which can continue for many hours. Larger burns cause systemic hypocalcaemia and hyperkalaemia and death has been reported from burns as small as 2.5% of total body surface area.
Following lavage with water, finger-nails should be trimmed and blisters de-roofed to ensure no acid is retained at the site of injury. Calcium gluconate or carbonate gel should be applied topically to neutralise the fluoride ions. This can be supplemented by subcutaneous injection of calcium gluconate. Failure to relieve pain by these measures indicates continuing damage and a need for surgical excision.

Late management

Some stiffness is common after complex burns have healed and physiotherapy will need to be continued. Static splints can help maintain web-spaces whilst wound-maturation occurs and dynamic splints can assist in the mobilisation of recalcitrant joints.
Burn-wounds are prone to hypertrophy. This should be controlled by the application of customised pressure garments which need to be worn for much of the day.

Inadequate primary care inevitably leads to skin and joint contractures. Common problems include flexion of the proximal interphalangeal joint, extension of the metacarpophalangeal joint, distal migration of the inter-digital webs ("web-creep") and tightness of the first web limiting thumb abduction. Surgical correction of these problems can be complex and may involve multiple procedures, particularly in growing children.

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