Although the majority of burn wounds undergoing surgical treatment require only excision with split-skin grafting, the introduction of free microvascular tissue transfer has allowed for the preservation of otherwise unsalvageable deep burn injuries and the resurfacing of burn scars in areas with no available local tissue. A total of 1699 patients with burn injuries were admitted to the Burns Unit in Newcastle upon Tyne in the 5 years 19891993. During this period 604 patients (35.5 per cent) required surgical treatment of their burns. Of these patients 582 (96.4 per cent) underwent excision of their burns with split-skin grafting, 13 (2.1 per cent) of the patients required local flap cover and nine patients (1.5 per cent) had free tissue transfer. Free flap loss in this study was 22 per cent in burns patients as compared to only 3 per cent in patients undergong microsurgical reconstruction for other reasons.

Introduction
Since the early 1970s, and more so in the last decade, the use of free tissue transfer techniques has expanded to include all areas of surgical endeavour and the acquisition of microsurgical skills has become a standard facet of plastic surgical training. Burns care has also witnessed the expanding role of free flap surgery not only in the secondary treatment of burns scars but also as a primary surgical treatment in deep burns (1). Free flaps can be used to replace the complex tissue loss resulting from a deep burn that exposes bone, tendons or neurovascular structures, which are unable to support a free skin graft (2). The commonest causes of such burns are electrical injuries or contact burns in the unconscious patient. In secondary burns surgery, free flap transfer may be used to reconstruct tissue deficits, for example, toe to hand transfer to reconstruct a lost thumb or the use of a free flap to bridge a defect following release of contracture (3,4).

There has been much debate recently concerning the future provision of burns care in the UK and what facilities should be available in the ideal burns unit (5,6). Based on our experience in Newcastle, we have sought to clarify the position of free tissue transfer in the management of patients presenting with burn injury and put into perspective the value of microsurgical facilities in burn care.

Patients and methods

Details of all patients admitted to the burns unit in Newcastle upon Tyne were collected for the period 198993 and an existing computerized database of free flap patients, allowed identification and retrieval of information on those pateints having free flap surgery for burns.

Results

A total of 1699 patients were admitted to the Burns Units in Newcastle upon Tyne during the 5 year period from 1989 to 1993 (Table I). Of these, 1095 patients (64.4 per cent) were treated non-operatively and 604 patients (35.6 per cent) underwent surgery.

A total of 582 patients (96.4 per cent) required only surgical excision with split-skin grafting, 13 patients (2.1 per cent) required local flap cover and only nine patients (1.5 per cent) had a free microvascular flap. The number of free flaps carried out for burns represented only 4.8 per cent (9/186) of the total number of free flaps performed in our unit during this period. Of the 186 free flaps carried out, the largest number were for head and neck cancer resections (Table II)

Nine free flaps were carried out for the treatment of burn-related injury (Table III). Of the four patients undergoing primary surgery for their injuries with free flap cover, there was one contact burn (patient underwent two free flaps), one scald and two friction burns. Four patients had free flaps for secondary treatment (release of burns scarring).

Case reports

Case 1
An 18-year-old male was involved in a road traffic accident and sustained a 3 per cent body surface area burn to his left foot from hot engine coolant fluid that leaked onto his trapped leg (Figure 1). Initial debridement exposed extensor tendons and tarsal bones, leaving a 14 cm x 9 cm defect on the dorsal surface of the foot. Cover was provided by free transfer of latissimus dorsi muscle anastomosed to the posterior tibial vessels, with split-skin graft on the surface. The result at 6 weeks postoperation is illustrated in Figure 2, the bulk of the muscle has already diminished allowing him to wear custom-made shoes.

Case 2
A 22-year-female sustained a burn to the right elbow from an electric light bulb whilst unconscious from an overdose. Initial treatment consisted of debridement, including medial epicondyle resection, ulnar nerve grafting and coverage of the defect with a free left latissimus dorsi muscle transfer. An external fixator was used to stabilize the elbow joint. This flap broke down over the medial epicondyle and an ipsilateral pedicled latissimus dorsi flap was used to provide cover.

*p=0.002 Chi square test.

The patient remained healed until at 6 months she presented with recurrent areas of skin breakdown. Radiographs confirmed the presence of chronic osteomyelitis. In conjunction with orthopaedic surgeons, a radical resection of involved bone was performed and the defect reconstructed with a free fibular osteocutaneous free flap, which failed on day 5 from problems with venous drainage. A salvage rectus abdominis flap was unsatisfactory and she subsequently underwent amputation of her arm.

Discussion
This study has confirmed that free tissue transfer is required for only small numbers of burned patients. For these patients the benefit of early wound coverage of complex defects can be great, and in secondary surgery following scar release, extensive areas of tissue deficit can be covered. Free flap surgery is technically demanding, requires intensive aftercare and an experienced team approach (7). In our unit, where free flaps are regularly performed, there has been a 22 per cent (2/9) failure rate in free flaps on burn patients. Table IV summarizes the previously reported experience of free flaps in burns patients that have appeared in the literature. Series with four or more cases are quoted and an overall free flap failure rate of 11 per cent is shown from a total of 101 patients.

These failure rates are significantly higher than those for free flaps performed for other procedures. Our own series from 1977 to 1989 had a failure rate of 8 per cent (7) for all indications, and from 1989 onwards in over 200 patients there has been a 3 per cent failure rate in our unit. Comparison of burn and non-burn cases over the study period 198993 (Table II) shows a significant difference in free flap failure rates P<0.05 (Chi square test), although the numbers are small and therefore the result statistically unreliable.