Single-Stage Composite Reconstruction Of Complex Electrical Burn Defects By Microvascular Techniques – A Prospective Study

Summary

Electrical burn constitutes a major proportion of patients admitted to the burn ward with life- as well as limb-threatening complications. Due to the severity of an electric current passing through the body, local tissues are greatly damaged. These patients require multiple debridements and surgeries to cover the composite defect resulting from a high voltage electrical contact burn. In our study, we intend to evaluate the application of microvascular reconstruction by doing a free tissue transfer on an electrical burn defect, and determine how doing a composite reconstruction of a complex defect in a single stage helps in decreasing morbidity.

Introduction

Electrical injuries constitute 3-4% of patients admitted to burn units, and the extremities are affected in more than 70% of cases.¹ The severity of this injury is dependent on several factors: the type of circuit, the voltage or intensity of the current, the resistance of the body, the value of the current, the pathway of the current, and the duration of contact. These factors are so interrelated that analysis of each of their clinical effects separately is impossible.²

Extensive coagulation necrosis of the skin at the contact sites is only part of the total injury from high voltage current. Passage of the current through the body causes damage, to a greater or lesser degree, to skin, nerves, blood vessels, muscles, bones, tendons, chest, abdominal viscera, and the central nervous system. The more resistant the tissue, the more heat is generated as the current flows through it. Larger blood vessels usually remain patent, but the walls are damaged and mural thrombi form. Delayed rupture and hemorrhage are often seen. Small vessels are damaged but may be thrombosed. Muscles show patchy necrosis. Various extended areas of myonecrosis, not directly near the current flow, are the result of decreased vascularity from small artery or vein thromboses.³

As a result of this injury, there is exposure and devitalization of underlying vital structures such as bones, joints, tendons and nerves, which can result in permanent disability and limb amputation.⁴ So in an electric contact burn, what we get is a composite defect with loss of soft tissue as well as vital tissues like tendon, nerves, muscle or bone.

For such a composite defect, radical debridement followed by multiple-stage surgeries is carried out. Free flaps can provide and replace the lost tissues in a single stage and hasten the recovery of the patient by avoiding multiple procedures, thus achieving early return to work.

Aims and objectives

In our study, our aim is to ascertain the impact of microsurgical reconstruction in electric burn patients in terms of quality of reconstruction, and also to determine factors for decision making for a successful microsurgical reconstruction in this unique cohort of patients.

Materials and methods

This is a prospective study including patients admitted to the Burns Ward in SMS Hospital, Jaipur, with an electrical contact burn from 2016 to 2020. All patients undergoing microvascular free flap reconstruction for high voltage electric burn injury were evaluated in terms of flap survival, time interval between burn injury and surgery, site of defect, type of flap used, number of components transported along with the flap, and number of tissues reconstructed. All microsurgical free flap transfers and the initial debridement were carried out by a single surgeon (1^st author).

Patients who had sustained low voltage, electric flash injuries were excluded.

Results

A total of 34 patients underwent microvascular free flap reconstruction in the above-mentioned time period, the sample predominantly consisting of males (26). Patients included in our study were in the age range of 10 years to 56 years, mean age being 25 years. Mean ischemia time, which was defined as the time period starting from ligation and division of pedicle to revascularization of harvested flap, was 41 minutes, while average time taken for all the surgeries from starting the procedure to end was 234 min (3 hours 54 min).

Out of a total 34 flaps, 29 flaps were successful, while the remaining 5 proved a failure, success rate being 85.29%.

Flap cover was classified according to timing of surgery after the initial electrical burn injury into primary (up to 6 weeks) and secondary reconstruction (more than 6 weeks). Primary reconstruction was further classified into:

• Immediate – within 5 days

• Early – 5 to 21 days

• Intermediate – 21 days to 6 weeks.

As shown in Table I, the immediate group had an 83% success rate, the early group 88%, the intermediate group 80%, while the secondary reconstruction group had an 85% success rate.

Table I. Distribution of patients according to the timing of surgery along with success rate.

Overall success rate was 85.29%. Fig. 1 reports success rate among the various groups based on the timing of intervention.

Fig. 1. Timing of flap cover with success rate.

The most commonly affected regions were the extremities (upper and lower limb combined), comprising of 19 out of a total 34 cases, followed by the head and neck region (13), as shown in Table II.

Table II. Areas involved and success rate.

Success rate among the various defect sites was calculated and is shown in Fig. 2. In total, six types of flap were used, among which the most commonly used was the lattisimus dorsi myocutaneous/muscle flap (13), followed by the anterolateral thigh flap (10), radial artery forearm (6), parascapular (2), osteocutaneous free fibula (2) and profunda artery perforator flap (1).

Fig. 2. Bar diagram showing area-wise result.

As shown in Fig. 3, the most commonly used flap in primary reconstruction was the lattisimus dorsi myocutaneous/muscle flap, while in secondary reconstruction it was the ALT fasciocutaneous flap.

Fig. 3. Pie chart depicting type of flap used.

The overall complication rate as shown in Table III was 38% (13), including both early and late complications. Seven free flaps were re-explored, out of which 2 free flaps were salvaged. Late complications were managed with dressings, antibiotics and secondary suturing. Out of a total of 34 flaps, 22 flaps were composite flaps consisting of 2 or more than 2 components, as shown in Table IV. One case required a free tensor fascia lata graft to cover the exposed dura. In two cases of forearm reconstruction, free functioning muscle transfer was done for wrist flexion, while in two cases, free sural nerve graft was used to repair he injured median nerve.

Table III. Complications encountered in the study.

Table IV. Different components used in the study.

Discussion

Although most burn wounds are covered by a split thickness graft, electrical burn injuries often result in complex wounds with exposed vital structures that are not amenable to skin grafts.⁵ Their destructive nature also limits the availability of healthy tissue in the close vicinity of the defect, thus limiting the use of local flaps. Complexity and extensive defect size following debridement are also major deterrents. The immobilization (up to 3 weeks) required using distant pedicle flaps such as the groin flap, hypogastric flap and cross leg flap can halt early rehabilitation, prolong tissue oedema, and increase joint stiffness, all of which can lead to suboptimal functional recovery along with the need for further secondary surgeries. So, conventional treatment modalities like local and distant flap cover entail longer hospitalization, increased morbidity, and multiple operative procedures with less than ideal results.

In recent decades the use of free flaps for reconstruction in burn patients has increased due to advances in the field of microvascular free tissue transplantation.^6,7 As a result, free flaps have reached a high level of sophistication. Fascial flaps, preexpanded flaps, functional muscle transfer, composite tissue flaps, multiple flap transplantations in the same patient and combined flaps (‘chimeric flaps’) based on a single vascular pedicle have been performed in patients with large defects of an extremity.⁸

Free tissue transfers for severe electrical burns are often the only option and are an essential component of modern burn care.⁹ Free flaps also play an important role in limiting functional impairment through maintenance of maximum bony stump length.¹⁰ Also, quality tissue coverage can be provided while offering good gliding planes, which are necessary for upper-extremity primary or secondary reconstructive procedures such as tendon grafts and transfers. Most importantly, free flaps can provide multiple tissues in a single-staged reconstruction, thus enabling early recovery of both form and function.

To our knowledge, ours is the largest study to date, involving 34 free flaps for electrical contact burn reconstruction by microvascular techniques, in which we achieved a success rate of 85.29%. This is comparable to the current trends.

Pessoa et al. performed 18 free flaps and achieved a success rate of 88.9%,¹¹ while Ofer et al. performed 26 free flaps on electrically injured limbs and achieved a success rate of 85%.¹²

Timing

There have been different opinions about the ideal timing for burn reconstruction. This is mainly because in the acute phase of burn injury, the challenges faced during the reconstruction are different than when done at a later time, like infection, vessel patency and limb /life salvage. In our study, reconstruction of electrical burns is classified as primary and secondary reconstruction (Table V). This classification was based on previous literature reports.^13,14

Table V. Patients divided according to timing of flap cover.

In our study the success rate in the primary and secondary groups was similar, 85% and 85.71% respectively, which is in contrast to previous studies that have shown better results in the secondary group.

In the primary group, success rate was slightly better in the early group (88%) when compared to the immediate (83%) and intermediate (80%) groups, but the differences were statistically not significant. This finding also goes to show that with a logical flap selection, proper patient selection and recipient vessel selection, timing of the flap cover is not a deterrent to proceeding to free flap cover in the early period.

Handschin et al. recommended caution for the first four weeks of the trauma and advocated that this four-week period is likely to have a progressive intima lesion, potentially hazardous for free flap survival. ¹⁵ Similarly, Sauerbier et al. concluded that primary reconstruction with free flaps has slightly higher complication rates in their mix burn and high power electrical burn injury series, but it is worthwhile to do complex microsurgical procedures in order to salvage extremities.¹³

Meanwhile, Shen et al. showed no significant relationship between flap failure and timing of the surgery in their series with 54 patients (17% flap failure) consisting of mix cases of burn, electrical burn and trauma.⁵

Jabir et al.¹⁶ also did not find any relation between he timing of primary reconstruction and flap survival. According to his study, the rate of failure was more related to inadequate early debridement rather than to the timing of reconstruction.

While some authors like Shen et al.⁵ and Jabir et al.¹⁶ reported high success rates for free flap coverage performed in the first 10 days after burn injury, others such as Baumiester et al.,¹⁴ Ofer et al.¹² and Sauerbier et al.¹³ recorded a higher risk for complications between day 5 and 21. Their hypothesis for this increased failure rate includes an increased infection rate at the recipient site, augmented intravascular thrombogenicity, and amplified posttraumatic vascular affection during this time period.

However, in our study we found that free flap survival had no relationship with timing.

History suggests that part of the reason why there has been a reluctance to carry out early free tissue transfer is because of the concept of “progressive tissue necrosis” following electrical burns, which has become ingrained within the surgical community.

This concept can lead to many patients having to stay in hospital for longer periods of time, increasing the cost, morbidity and danger to limb/life as well. In our view, ongoing tissue necrosis in electrical burn injuries is a sign of missed or inadequately debrided wound.

This can be attributed to the following reasons:

• Inadequate fasciotomies

• Inadequate initial explorations

• Proximal deep muscle injury that was not explored initially

• Subjective observations of viability

• Debridement itself that devascularized surrounding muscle

In our opinion, the most important factor for the success of free tissue transfer in electrical burns is extensive and radical debridement and removal of all non-viable and doubtful tissues as soon as possible, as shown in Fig. 4.

Fig. 4. Electrical burn defect to right forearm with debridement followed by a free ALT flap cover.

Ongoing tissue necrosis in electrical burn injuries is more a reflection of missed or inadequately debrided devitalized tissue. In the early 1970s, three groups investigated the concept of progressive vascular injury using serial arteriograms.^17,18,19 Injuries seen initially on arteriograms do not progress on serial studies of the same patients.

Clinical studies by Luce and Gottlieb²⁰ could not corroborate findings of progressive tissue necrosis. Elegant primate studies were done by the McGill University Group in the early 1980s and concluded that there was no evidence for progressive muscle necrosis.^21,22 Chick et al.⁹ in his study in 1992 concluded that early extensive debridement and flap coverage of electrical and severe thermal burns will give improved results and lessen morbidity when compared with older protocols involving serial debridements. According to him, progressive tissue necrosis is an outmoded concept that should not alter basic surgical principles.

In the study done by Koul et al.,²³ 16 free flaps were used for acute burn reconstruction following electrical injury. There was one flap failure, but flap survival rate exceeded that mentioned in other recently published studies (77-91%).¹⁴ Failure in their series followed infection and secondary haemorrhage, and was not due to vascular occlusion. Otherwise all flaps survived without any flap-related complication. This supports the argument that the concept of progressive tissue necrosis or progressive vascular occlusion is false.

Extensive compartment release through fasciotomies and escharotomies with nerve decompression in selected cases is imperative at admission for acute burn. This should be followed by early surgical exploration of the extent of injury and aggressive radical debridement followed by flap cover.

We recommend that an electrical burn defect should undergo debridement as soon as physiological stability is achieved, and it should be carried out by a senior plastic surgeon. Debridement is thought to be a not-so-complex surgery and is left to be done by the most junior surgeon in a plastic surgery team. This should not be the case in an electrical burn wound as a senior plastic surgeon’s experience can help to identify and debride all the non-viable and doubtful tissues in one sitting which, if left behind, can be a cause of flap failure and increased morbidity. We follow these protocols in our setup and it has given us good results in the primary group, especially in the immediate time period (<5 days). But in our experience, we should avoid proceeding with a free flap cover in the first 72 hours as this period should be utilized for fluid resuscitation, finding any associated injuries and, most importantly, damage to soft tissue and the vital structures becomes quite clear. Difference between viable and non-viable tissues is quite evident at around 72 hours. Also, it gives an adequate amount of time for the team and the theatre attendants to prepare for a major surgery.

Meanwhile, in secondary reconstruction, the initial inflammatory response has settled and scars have matured, and we get a better quality skin with a softer texture that lends itself more readily to surgical manipulation (Fig. 5). Also, chances of infection are much lower. In our study, the success rate in secondary reconstruction is 85.71%, which is comparable to the other studies.

Fig. 5. Post electrical burn deformity of face with a free RAFF.

Choice of flap and need for composite reconstruction

Once adequate wound debridement/excision of scar has been done and the need for free tissue transfer has been established, selection of the most adequate flap is dependent upon the same considerations made for any other patient with tissue loss: size and anatomical location of the defect, available flaps for harvest, and functional and aesthetic outcomes regarding both the donor and recipient areas. In electrical burn, the underlying vital structures like nerve, muscle tendons and bone are also damaged and need to be reconstructed as well for optimum results. While in the case of burn over the face, a thin pliable flap like a radial artery forearm flap would suffice (Figs. 5 and 6). Thus, this unique cohort of patients requires a composite reconstruction by replacing all or most of the components, and requirements are different in each case.

In keeping with these principles, 22 out of the total 34 flaps were composite flaps that had two or more components. Fourteen flaps were either muscle or myocutaneous flaps (LD), while two were Osseo cutaneous flaps containing fibula bone for skeletal reconstruction. In two cases, median nerve was reconstructed using a free sural nerve graft and in two cases a functional muscle transfer was done for wrist flexion (Fig. 7). In one case, a free tensor fascia lata graft was used to cover the dura, while in one case a flow-through flap was used for limb salvage. Choice of free flap depends on the individual case and the amount of tissues lost. Whenever there is a significant three-dimensional defect to be covered, muscle flaps provide well-suited tissue for filling the dead space.^16,24 They are also preferentially used in primary reconstruction due to a faster healing rate.²⁵ The most commonly used flap in our study was the Latissimus dorsi flap (14 patients). A free flap provides a healthy, well-vascularized tissue from outside the zone of injury and various tissues can be transferred in a single stage like vascularized bone, skin, muscle and nerve, providing a one-stage solution to complex injuries and potentially diminishing the chance of infection, reducing the length of hospital stay and facilitating early mobilization and rehabilitation.¹⁸

For example, in the case of forearm reconstruction, wrist flexion along with hand function should be the optimal functional aim, which can be achieved by either a free functioning muscle transfer or by using a nerve graft for median nerve repair. Damaged tendons can also be replaced using tendon grafts and subsequently covered by a free flap. Thus, microvascular techniques provide many options for an ideal functional recovery to an electrically injured area and, most importantly, it can be done in a single stage. Our study goes to show that if adequate debridement has been achieved, then the chances of failure are minimal and thus we can combine multiple surgeries and provide all the tissues in one sitting.

Fig. 6. Acute electrical burn over face with early debridement and covered by free RAFF.

Fig. 7. Defect over right wrist and a free functioning LD flap cover for wrist flexion.

Conclusion

Microsurgical free tissue transfer has an invaluable role in burn reconstruction due to paucity of nearby healthy tissues and the composite nature of the ensuing defect.

In primary reconstruction, early wound debridement and free tissue transfer can help preserve underlying vital structures and improve the patient’s physiological status.9An early intervention can help preserve the vessel patency, and maintain nerve continuity and limb salvage in properly selected patients. Instead in secondary reconstruction, free flaps can sometimes be the only option for providing the necessary quantity of healthy tissue to achieve the aesthetic results needed in this group of patients.

Choice of flap should be determined only after radical debridement has been done and the number of components lost enumerated, which is possible only after debridement. Planning for replacement of all the lost tissues should be sought on the table. A composite flap choice should be made so that most of the components lost are replaced in the same sitting.

In conclusion, electrical burn wounds present with a complex defect that provides a challenge in terms of functionality, tissue preservation, infection and danger to limb/life of the patient, as well as a good cosmesis. Microsurgical free flap transfer gives us the option of achieving all of these goals in a single stage, which would help the patient make an early recovery with significantly less morbidity and less time spent in the hospital.

Limitations

The design of the study comprises both primary and secondary reconstruction groups, which need to be studied separately as each of these groups has different challenges and requirements to achieve an ideal reconstruction. The small number of patients is also a limitation of the study, as detecting statistical significant difference is difficult in the current set of patients.