During the development of this material, several unexpected...

During the development of this material, several unexpected outcomes were observed. The synthetic composition means that it is not prone to attack by microorganisms (it is not a ‘foodstuff’). Thus, infection is uncommon and, if it does occur, is localised and manageable without loss of the matrix.16,22,23

Increasing burns use also demonstrated that loss of skin graft over the integrated BTM is extremely rare and that the appearance of autograft mesh pattern (even with widely meshed graft) is considerably better than autograft alone.22 This finding has also been observed with collagen-based matrices and has its basis in the principles of wound healing

Deep wounds (deep dermal and full-thickness burns, for example) are characterised by two features—the complete absence of any residual epidermal potential within the wound and a poor dermal structure, which preclude epithelialisation. It is probably the reason that edge epithelialisation only occurs approximately 5 mm from the edge of a deep wound, and why epidermal (keratinocyte) sheets and suspensions (whether cultured or non-cultured) have no value in the primary treatment of deep dermal and full-thickness burns. In untreated deep burns, once the lengthy autolysis and separation of eschar have occurred, the wound therefore heals by secondary intention, with granulation tissue formation, myofibroblast differentiation and contraction, processes designed to approximate the wound edges so that final epithelialisation can occur. This results in prolonged healing time, contracture and hypertrophic scarring with functional disability, unacceptable dysaesthesia and symptoms of pain and itch.18 Repeated scar breakdown and infection are common. In this group of burn patients, our priority as surgeons is to abort the inevitable secondary intention healing and replace it with a primary intention solution—the sheet autograft. Once in situ, the graft heals by primary intention around its edges and its deep margins. When we mesh autograft, the struts of the graft heal similarly, but the larger the mesh ratio, the larger the interstices (the diamond shaped gaps between the graft struts). The bed of the interstices is the same as the original wound bed and thus incapable of sustaining epithelialisation from the struts without structural alteration, and granulation tissue ‘blebs’ thus develop to facilitate epithelialisation. The wider the mesh, the more extensive the ‘blebs’, the worse (or more ‘cobblestoned’) the cosmetic appearance, and the greater the interstitial contraction. The presence of a ‘neo-dermis’ provides a bed across which interstitial epithelialisation can occur without needing granulation tissue and so the cosmetic appearance is improved. In fact, the thinner the graft, the better the appearance and the less obvious the mesh pattern.

The development of the NovoSorb™ BTM began at the end of 2004, but it was not until 2014 that it was first used in (significant) burn injury.21 Human experience before this time was limited to small, complex surgical wounds (free flap donor site reconstruction).15,16 The burn situation is very different. The patients have suffered major trauma with complex pathophysiological insults, often complicated by smoke inhalation injury or other trauma. As such, the decision was made that the first burn exposures would be restricted—BTM would not be applied to highly important functional areas (the hands or the neck), areas of great cosmetic importance (the face), or zones where previous dermal matrix use has proven impossible or highly problematic without issues caused by untenable patient positioning (the posterior trunk/buttocks). Our early burn experience has been documented, as have our experiences in the reconstruction of significant and complex wounds (e.g. after necrotising fasciitis debridement).19,20,22,23 In the initial, five-patient significant burn trial, our concerns regarding the use of BTM on the dorsum of the hands proved unfounded, and excellent hand function was demonstrated.21 The fourth and fifth trial patients also reassured us that the BTM was an excellent material for the posterior surface of the trunk and buttocks without needing to position the patient prone to avoid shearing and pressure effects on integration.21 In fact, BTM seems to integrate more quickly in these areas, possibly due to compression against the bed. The results of fascial neck reconstruction with BTM in burns and necrotising fasciitis patients have made this our primary recourse.20,22

One throwback to our previous use of dermal matrices remained—we were convinced that the matrix should be used to cover areas where there was insufficient autograft for coverage, using the matrix merely to ‘patch’ and actively temporise debrided but ungrafted wounds while donor sites healed for re-harvest to allow their definitive closure. This practice had developed for two reasons; primarily, because of the exorbitant cost of collagen-based dermal matrices7 and, secondarily, because of the predilection of collagen-based dermal matrices to become infected (30%).8,9 The thinking thus was to definitively close whatever could be closed with available autograft and temporise the rest, despite the obvious downsides elucidated earlier in this text. It was not until the 13th burn patient that this practice was demonstrated to be deleterious to patient outcome, effecting a paradigm shift in our thinking, and prompting a radical change of practice.

Patient 13 was admitted with 70% TBSA full-thickness burns (Figure 1(a)). The entire burn was debrided on arrival. Three days later, our confidence with BTM had grown to the point that his burns were gently refreshed and the available autograft donor sites (his back and buttocks) were harvested. Sheet autograft was applied to the dorsum of his hands and digits. The remaining graft was meshed 1:2 and applied to debrided burn on chest and abdomen (Figure 1(b)) (consent has been obtained from the patient to publish his clinical pictures). The debrided, ungrafted wounds (50% TBSA) received BTM (Figure 2(a, b)). The grafts took completely (Figure 3(a, b)). On Day 38, the BTMs of his upper limbs, shoulders and lower limbs below the knees had their seals removed, his donor sites were re-harvested and the 1:2 meshed autograft raised was applied (Figure 4(a, b)). A week later, the grafts on BTM were robustly taken (Figure 5). On Day 50, the remaining BTM (circumferential thighs) was delaminated and covered with 1:2 meshed autograft. No autograft was lost at any stage. The patient left the burns unit, completely healed, on Day 91 post-injury.

He visited frequently for outpatient review, initially from his inpatient rehabilitation facility, then from home. Over the few months after discharge, the graft over the chest and abdomen (applied at Day 3 post-injury) began to become stiff, tight and mildly hypertrophic. By nine months, this change was stark because the adjacent BTM grafts were soft, supple and elastic (Figures 6 and 7). His full range of axillary motion was marred only by tightness within his trunk grafts (Figure 8(a)). The difference in cosmetic appearance persisted (Figure 8(b)). We realised that, if graft applied over BTM five weeks after graft applied to debrided burn is softer, more elastic and cosmetically superior, and not just in the short term but also after several years, then early grafting is not only unnecessary, it is deleterious.