often requires grafting. It is important not to use widely meshed skin in this area as any significant hypertrophic scarring can cause difficulties with weight bearing ambulation and fitting of shoes.

The burnt hand requires attention to detail must to achieve optimal functional and cosmetic results. The volar aspect of the hand is covered with specialized glabrous skin, which usually heals and it is best to avoid grafting it if possible. The dorsal skin is thin and usually requires grafting in deep burns. In general, sheet graft is preferable to mesh graft and is best secured with absorbable sutures. Mesh interstices should run longitudinally along the hand and digits. The key to functional success is early mobilization of the hand. Initially after grafting the hand is dressed and splinted in the position of safety with the metacarpophalangeal joints flexed at 70–90°, the interphalangeal joints at 180°, the wrist in neutral or slightly extended and the thumb flexed and adducted at the metacarpophalangeal joint. The grafts are inspected at five days and, if stable, mobilization can be started. If sheet grafts are used they can be exposed with no dressing during mobilization during the day with splintage at night.

In patients with large burns, repeated application of allograft may be required until it is time to autograft the hands. It can be very difficult to maintain the position of safety of the hand during this phase and K-wires through the metacarpophalangeal and interphalangeal joints may be required to maintain the joints in optimal position.

The face and neck are areas that are both cosmetically and functionally important and are discussed in greater detail later on in the book. Deeper burns of the face will often benefit from early excision and autografting. Medium to thick sheet split skin autograft should be used for the face and applied in cosmetic units to place marginal scars in natural skin crease lines. If available, donor sites should be above the neck for optimum color and texture match. The scalp is an excellent donor site for grafts destined for the face. The use of skin substitutes like Integra have been describes as giving superior cosmetic outcomes.

Early excision and closure of eyelid burns reduces the incidence of corneal injury secondary to exposure and should be a priority. When applying autograft to the eyelids thick split thickness graft

should be used and overcorrection should be performed putting more skin in than seems to be needed as contraction can lead to corneal exposure.

Skin replacement

Following wound excision it is vital to obtain wound closure. Wound closure can be permanent using autologous split skin graft or temporary using allograft or skin substitutes. Physiological closure of the burn wound reduces invasive infection, evaporative water loss, heat loss, pain and promotes wound healing. Temporary skin substitutes are used to achieve physiological wound closure following excision until donor sites have regenerated and are ready for harvesting. In general all these coverings buy time while the donor sites heal [38].

Autograft

In general autologous split skin grafts are the gold standard for resurfacing burns. However they have limitations and attempts are being made to resolve some of these by the development of skin substitutes. Split skin grafts can be harvested either as split thickness or full thickness grafts. Full thickness grafts tend not to be used for acute burns, as the donor sites requires closure, do not regenerate and are limited and their use is usually reserved for postburn reconstruction.

Split skin grafts take more easily, and are the mainstay for wound closure. Split skin grafts can be harvested either with a hand knife or with a powered dermatome. Skin grafts can be used as sheet grafts or can be meshed using expansion ratios of 1:1, 2:1, 3:1, 4:1, 6:1 and 9:1. Other skin expansion techniques such as the Meek technique have also been described as being beneficial.

Allograft

Allograft skin is a vital skin substitute and its use has been a key factor in improvement in the mortality associated with extensive burns [39]. Allograft skin is usually harvested from cadaveric donors after appropriate donor selection and screening for communicable disease, and consent from relatives has been

Fig. 6. Allograft Usage Index. Amount allograft used in cm2 per % Burn TBSA

obtained. Strict exclusion criteria are applied to ensure safety for transplantation.

Allograft skin is usually harvested, collected, screened, processed, and distributed by a regional tissue bank. Allograft is analogous to blood, and it is important to use this vital resource responsibly. The amount can be estimated by determining the body surface area and burn size in cm2. Recent analysis of total allograft use has produced an allograft index to aid planning [40] (Fig. 6).

Allograft skin can also be obtained from living donors, usually parents or relatives of burned children. It is usually harvested immediately prior to its use on the burn victim and is used fresh. In view of the reliable supplies of good quality allograft skin provided by tissue banks, this method is used infrequently.

Allograft skin can be used either as sheet or meshed graft. It is mainly used meshed 2:1, and care is taken not to expand the interstices to prevent desiccation, infection and necrosis of the underlying wound. Meshing the allograft allows any hematoma and seroma drainage. Sheet allograft tends to be used to cover cosmetic areas such as the face as even with unexpanded mesh granulation tissue can grow through the interstices and leave a permanent pattern.

Integra

Integra is an acellular bilaminar structure that provides wound closure with permanent dermal replacement [41]. It is made of an upper silicone layer that acts as a temporary epidermis providing control

Fig. 7. Use of Integra® in Patient with 70% TBSA Burn.

A Following application, Integra® Revascularised; B Following Autografting, Wound Healed

of evaporative water loss acting as a barrier to microorganisms. The bottom layer is a cross linked matrix of bovine collagen and chondroitin-6-sulphate. This becomes incorporated into the wound and is termed a ‘neodermis’. This skin substitute is used to replace dermis in full-thickness burns in an attempt to modulate post burn hypertrophic scarring.

After excision of the burn Integra is applied to the wound in a similar fashion to autograft. Care is taken to avoid wrinkles or pleats in the Integra and it is secured to the wound with either skin staples or sutures. Non-shear dressings are then applied and silver based dressings are applied to the covered areas on a regular basis to try and limit contamination, colonization and infection of the Integra covered wounds. The Integra should be inspected daily during this time. Any collections occurring under the

matrix should be aspirated and sent for microbiological culture. If any purulent material appears under the Integra or if it becomes non adherent, then it should be removed, the underlying wound cultured and the Integra replaced with allograft skin.

The collagen/chondroitin-6-sulfate matrix is vascularised by host cells over the next three weeks or so and the artificial dermis is gradually replaced with a ‘neodermis’ which is pink and flat. No granulation tissue should be seen. When the ‘neodermis’ looks vascularised and has a healthy pink colour, the silastic covering can be removed and very thin epidermal autografts (2–4/1000 inch), containing epidermis only can be harvested and applied. This provides epidermal cover for the ‘neodermis’ and produces permanent wound closure (Fig. 7). The grafts are susceptible to loss at this stage and silver based dressings are applied over a non-shear dressing.

Integra has been extensively studied and has produced encouraging results both in single centre studies and in a multi-centred randomized controlled trial [41]. Studies have reported less hypertrophic scarring with a much more pliable resultant scar and a reduced requirement for secondary reconstructive procedures [42], however, this concept has never been demonstrated fully even with over 20 years of use. Integra is expensive, but when successful it has been shown to provide a durable, long-term result, with some suggestion of reduced hypertrophic scarring and pruritus [42].

Integra has also been used in post burn reconstruction, especially for in patients who have limited availability of donor sites [43].

Matriderm

Recently synchronous application of dermal substitutes and skin graft has been established as a standard procedure. Matriderm , a bovine based collagen I, III, V and elastin hydrolysate based dermal substitute has been used with simultaneous application of split-thickness skin graft [44] (Fig. 8). This approach obviates the need for a second procedure for application of autograft. In a recent pilot study 20 wounds in 10 patients with severe burns were treated with either simultaneous transplantation of Matriderm and split thickness autograft or split thickness autograft alone after appropriate excision of the burn

Fig. 8. Matriderm® for Deep Burn to Hand. A Deep burn to left hand; B Following excision and application of Matriderm®; C Following application autograft over Matriderm®; D Post Op picture at 3 months including right hand treated with autograft alone; E Good early functional result

wound. The study concluded that simultaneous application of a dermal matrix is safe and feasible, yielding significantly better results with respect to skin elasticity [45]. A similar Integra one stage collagen based single stage dermal replacement product has also been produced but at the time of writing is not widely available.

Other skin replacements

Alloderm is a commercially available form of de-epi- dermalised de-cellularised sterile human dermis. It can be used as a dermal replacement for acute care and for post burn reconstruction [46]. In acute cases the burn wound is excised and prepared as usual. Alloderm is applied to the wound and a thin (epidermal) split skin graft is applied over it. This bilayered graft is secured and managed as skin graft. The dermal portion must be initially revascularised from the wound bed before vascularisation of the epidermal graft. This makes the technique prone to epidermal loss due to desiccation and infection prior to vascularisation of the epidermal graft. The amount of wound covered is usually limited to the amount of autologous split skin available for harvest. This has limited its success in the management of acute burns especially those involving a large surface area. It has been used more successfully in post burn reconstruction.

Amnion is the inner layer of tissue that surrounds the foetus in utero, and contains amniotic fluid. Both the inner amnion and the outer chorion layers have been used for many years, but amnion is preferred because it is immunologically privileged and less antigenic. Amnion is commonly used by Ophthalmologists to cover damaged corneas as it is immunologically privileged tissue and does not stimulate rejection. Amnion can control evaporative fluid loss and is effective in reducing bacterial counts. It also contains many growth factors that stimulate epithelial proliferation and has antiangiogenic properties.

In view of these specific factors its main use in burn care has been in partial thickness wounds such as donor sites and partial thickness burns [47]. It has not been extensively used following wound excision. Like any allogeneic material the risk of disease transmission must be recognised and managed. The limited availability, small size and fragility limit its usefulness in burn care. The majority of reports on its use in burn care have come from the developing world.

Although a variety of xenograft (sheep skin, frog skin) has been described as being used as a skin substitute, the only commercially available product is obtained from domestic swine. It has been processed in a number of ways to reduce antigenicity and prolong adherence. Processing has included irradiation, lyophilisation, glutaraldehyde-crosslinking and impregnation with silver. Porcine xenograft is available as either de-epidermalised dermis or complete skin. Depending on processing it can be stored in a refrigerator or at room temperature. Porcine skin xenografts have many of the same advantages as allograft skin. They can reduce evaporative water loss, limit infection, and encourage autologous epidermal growth. Porcine xenografts adhere to the wound be but will not vascularise. They are useful as a temporary covering for partial thickness burns, donor sites, and medical desquamating skin conditions but are not useful for excised full thickness wounds. They have a prolonged shelf life, are easy available and are relatively inexpensive when compare to human cadaveric allograft [48].

Cultured skin substitutes

Using tissue culture techniques, epidermal cells (keratinocytes) can be grown in a laboratory and

then used to assist wound closure [49]. From a 1 cm2 autologous biopsy, enough cells can be cultured in approximately 3–4 weeks to cover 1 m2 body surface area. Sheets of these cultured epithelial autografts or CEAs, have been used by burn surgeons for over 20 years [50].

These cells can be cultured commercially for patients with large burn injuries, however, the cost is significant. This technique only produces the epidermal layer for wound closure and, although there have been many reports of successful use of CEA to close burn wounds, a number of problems limit their use. The lag time of 3 weeks from biopsy to production of adequate quantities allows wound colonization and granulation tissue to develop leading to low take rates compare to split skin grafts. Once applied, the grafts are very fragile and often-prolonged immobilization of the patient is required. Even after successful take, the grafted areas remain fragile and blister easily due to poor and delayed basement membrane formation. Attempts to overcome some of these problems have been to graft the CEA onto an allograft dermal bed as described by Cuono in 1986 [51]. Initially after wound excision, allograft is used for temporary wound closure while CEA are produced. When ready, the epidermal portion of the engrafted allograft is removed using a dermatome or dermabrasion leaving a viable dermal allograft bed behind onto which the CEA are applied. This technique has been reported as having better CEA take with improved basement membrane formation and less fragility and blistering [51].

More recently the use of sub-confluent, autologous keratinocyte suspensions sprayed onto excised wounds has been described. This promising technique has been used directly to treat partial thickness wounds and excised wounds after excision. It has also been used to augment epithelialisation by treating interstices of widely meshed skin grafts and also skin graft donor sites. Initial results have been promising and many burn surgeons have moved from using sheets of CEA to this subconfluent suspension technique [52]. However confirmation of the superiority of this technique has yet to be confirmed by a multi-centred trial.

In general the use of CEA should be reserved for patients with massive burns with extremely limited donor sites or major burns where donor sites are