A Paradigm Shift in Practice-The Benefits of Early Active Wound Temporisation, page-34

Good evening folks; I am lucky enough to have access to the full-text through the University of Queensland, I will post the full-text for your viewing. Photos are graphic however truly remarkable.

Until very recently, the early definitive closure of wounds proved problematic when full thickness burns exceeded 50% of the total body surface area (TBSA). The mainstay of burn wound repair has been the split skin autograft and, at >50% TBSA, the burn area exceeds the donor site area. A number of manoeuvres have been established to facilitate coverage of these wounds by grafting, all of which are utilised in patients with the most extensive burn wounds—serial episodes of grafting surgery, harvesting very thin autografts (to allow more rapid re-epithelialisation of the donor sites, facilitating earlier re-harvest and allowing a greater number of harvests from the same donor site) and widely meshing the grafts, or using a Meek-Wall technique (Meek, Humeca, Enschede, Netherlands). This latter technique involves using small pieces of graft, placed in a specialised holder on a cork board and run through a series of blades perpendicular to each other, to create small squares of graft each 3 mm × 3 mm. Once cut, the holding platform can be pulled apart (to differing distances—the ‘mesh ratio’), separating the tiny grafts. Although ‘fiddly’ and laborious, this technique minimises graft wastage, since even small pieces of graft can be meshed in this way. Despite their utility and necessity, these techniques guarantee that the patient with the biggest burn survives with the poorest functional, aesthetic and symptomatic outcome possible.1

The use of cadaver skin to cover the non-grafted wounds pending donor site re-epithelialisation and ‘re-harvestability’ gained popularity in the late 20th century as issues of consent and techniques for harvest and storage (banking) were refined.2–4 The use of cadaver skin has a number of limitations. Skin banks are frequently short, or devoid, of stock. Its presence ‘passively’ temporises the wound, ‘buying time’ but not improving the wound bed, merely allowing undirected granulation. It cannot be used unless the patient is pathologically immune-suppressed, seemingly the only benefit to leaving the eschar in situ until the cellular and humoral components become inhibited by eschar-derived (Allgöwer) factors.

The dermal matrix strategy, pioneered by Jack Burke, sought to redress some of these issues.5 In producing a ‘scaffold’ to allow autologous tissue in-growth and establish a ‘neo-dermis’ (‘active’ temporisation), he improved the outcome of the thin, meshed skin graft.6 However, the material he (and Ioannas Yannas) produced (Integra Dermal Regeneration Template, Integra Lifesciences, Plainsboro, NJ, USA), which is a cross-linked bovine Type I collagen scaffold supported by shark fin chondroitin-6-sulphate glycosaminoglycan, physiologically closed with a bonded pseudo-epidermis of silicone, has a number of disadvantages. The first is the length of the processing time to manufacture the material, which thus renders it very expensive.7 The second is that placing non-vascularised biological material on the surface of a wound in an immune-compromised patient, and expecting neovascularisation to occur before infection does, is ambitious and frequently unsuccessful.8,9 Its use has therefore been limited; some surgeons have been unable to make it work consistently and thus, simply don’t use it. Due to cost, those surgeons that can make it work tend to limit its use to the biggest burns and then only use it to as a ‘patch-up’ to cover the wounds that remain following the primary grafting procedure. In this situation, the material is being used to temporise, because it physiologically closes the wound, reducing inflammation/proliferation and contraction. Since its integration improves the wound bed for subsequent closure, we can consider it to be an ‘active’ temporiser.

The principal misconception demonstrated by the production of Integra (and its subsequent analogues; Pelnac [Eurosurgical, Guildford, Surrey, UK], Terudermis [Olympus Terumo Biomaterials, Tokyo, Japan], etc.), is that, because dermis is being ‘replaced’ and the dermis structurally consists largely of Type I collagen and supporting glycosaminoglycans, the replacement must be composed of these materials, or a variation thereof (Hyalomatrix, Anika Therapeutics, Bedford, MA, USA). The long-term in vivo histology of these materials demonstrates that the exogenous collagen is absorbed and replaced by autologous collagen.10 The exogenous collagen thus provides a ‘scaffold’ for fibroblast ingress and neovascular growth, analogous to the scaffolding used by builders, i.e. removed once the ‘job’ is complete. A second analogous principle can be derived from the builders—the workmen do not move ‘in’ scaffolding pipes and decking boards, but within the spaces in between. Once this principle is grasped, that it is the spaces within the scaffold that are important, then the ‘temporary’ scaffolding itself becomes less so, and thus does not have to be of biological origin, but can be made of any biodegradable material as long as it is biocompatible, bio-tolerated and demonstrably safe (not cytotoxic, carcinogenic or teratogenic). Where biochemistry teems with potential materials, the properties of the majority are ‘fixed’ and cannot easily (cheaply) be tailored to alter, for example, their degradation rate. Organic chemistry, in particular plastic polymer chemistry, does offer the ability to tailor structure and properties but, until recently, biodegradability was elusive. Growing environmental pollution has forced the development of biodegradable polymers and, at the start of this millennium, Thilak Gunitillake at the Commonwealth Scientific, Industrial and Research Organisation (CSIRO) in Melbourne, Australia developed a family of biodegradable polyurethanes, now called NovoSorb.1 A completely synthetic, biodegradable polyurethane dermal matrix was designed and developed in Adelaide and is progressively becoming more available: the NovoSorb™ Biodegradable Temporising Matrix (BTM),1,11–23 produced by PolyNovo Biomaterials Pty Ltd, Port Melbourne, Victoria, Australia.