Elsevier

Burns

Volume 37, Issue 5, August 2011, Pages 873-881
Burns

Preservation methods of allografts and their (lack of) influence on clinical results in partial thickness burns

https://doi.org/10.1016/j.burns.2011.01.007Get rights and content

Abstract

Allografts, cadaver skin and amnion membrane are considered the golden standard in the management of partial thickness burns. However, debate on whether the tissue needs to be viable is on-going, since many believe that viable grafts result in better healing.

The objective of this literature survey was to analyse the evidence on the method of preservation of allografts (cadaver skin or amnion membrane, glycerol, cryopreservation, lyophilisation) having a clinical impact on the healing of partial thickness burns. The survey focussed on preservation techniques and clinical outcomes (reepithelialisation) in partial thickness burns, as well as on differences in viability, immunogenicity and antimicrobial properties of the preservation methods.

Most studies on allograft treatment of partial thickness burns are observational, with only one study of a (historical) comparative nature. A true meta-analysis was not performed and the results of this survey are observational in nature as well: they indicate that there is no evidence that viability of the graft influences healing outcomes. Thus, instead of viability, other aspects, such as intrinsic antimicrobial safety of the preservation method and cost should be the primary criteria for the choice of preservation method to be used for allografts.

Introduction

Allografts, also called homografts, are tissues or organs transplanted from a donor of the same species but of a different genetic constitution. In wound care in general, and burn care in particular, the primary types of allografts used are amnion membrane and cadaver skin.

With initial routine use dating as far back as the 1950s [1], [2], [3], [4], [5] the use of allografts is still a mainstay in the treatment of burns [6], [7].

The main indication for allografts is partial thickness burns [8], [9] where they are known to promote reepithelialisation [10], [11] and pain relief [12], [13], [14], [15]. Human allografts are also widely used for wound bed preparation [16], [17] after excision of deep dermal or full thickness burns and as an overlay over autografts in the sandwich or intermingled techniques [18], [19]. Although less commonly used than in burn care, allografts are also part of the armamentarium utilized in non-thermal trauma [20] and skin ulcer care [5], [21].

To assure reliable availability allografts are often stored in tissue banks [22]. Most commonly, glycerol and cryopreservation are used as storage and preservation methods. Both techniques have their own advantages and disadvantages but an essential difference between cryopreservation and 85% glycerol preservation is the level of viability of the preserved tissues [23], [24], [25]: glycerol preservation preserves the morphology of the cells but they are non-viable, whereas cryopreservation allows for a certain level of viability after the tissues are thawed.

Secondary analysis of the results of two surveys, conducted with 9 years separating them, on the type of allografts used in burn care indicates that cryopreservation techniques are primarily used in the United States, while most Western European burn centres prefer glycerol preservation [8], [9]. In many discussions with clinicians we largely have observed the same dichotomy. The “rest of the world” does not seem to have such a clear preference.

Those who prefer viable cells often state that the growth factors and other compounds delivered from these cells into the wound lead to superior clinical performance. Using the hypothesis that increased viability is reflected in better clinical performance, we have undertaken a review of the literature to analyse if any evidence exists that this hypothesis is, indeed, valid. We also looked at other aspects of preservation methods, such as antimicrobial and inflammatory properties that have the potential to contribute positively or negatively to healing results.

Section snippets

Methods

An extensive literature search was initiated, primarily on whether different preservation techniques used for amnion and cadaver skin lead to different clinical outcomes, with reepithelialisation speed, percentage of healing and long term results as the primary criteria.

We also searched for data on secondary aspects of preservation techniques which may have an influence on the primary outcomes, such as viability and immunogenicity of the tissues, antimicrobial properties and the potential of

Discussion and limitations

In total, 17 studies were found on partial thickness burns, treated with different types of allograft, with a total of 696 burns (Table 1).

Given that many consider allograft treatment the “golden standard [10], [11], [21], [71],” the number of published clinical trials is small. Moreover, the methodology of most of the trials was poor and outcomes studied diverse and ranging from days of hospitalization, reepithelialisation percentage and time, percentage of patients that had to undergo

Conclusion

The literature on allografts and clinical outcomes is of poor quality. The data collected in the studies are too diverse to allow for a true scientific comparison or statistical analysis. This is particularly surprising because of the existing convictions about superiority of one preservation technique over another. It is also because of these strong convictions that we felt publishing this overview was worthwhile, although we realize that the analysis of the literature itself does not follow

Conflict of interest

None declared.

References (87)

  • E. Pianigiani et al.

    Prevalence of skin allograft discards as a result of serological and molecular microbiological screening in a regional skin bank in Italy

    Burns

    (2006)
  • E. Mansilla et al.

    The derma project: present and future possibilities of skin procurement for the treatment of large burns in Argentina Tissue Engineering and the Cadaver Skin Bank

    Transplant Proc

    (2001)
  • D. Bravo et al.

    Effect of storage and preservation methods on viability in transplantable human skin allografts

    Burns

    (2000)
  • P. Rooney et al.

    Sterilisation of skin allograft with gamma irradiation

    Burns

    (2008)
  • H. Ben-Bassat et al.

    How long can cryopreserved skin be stored to maintain adequate graft performance?

    Burns

    (2001)
  • A.C. de Backere

    Euro Skin Bank: large scale skin-banking in Europe based on glycerol-preservation of donor skin

    Burns

    (1994)
  • M.D. Rosenquist et al.

    Skin preservation at 4 degrees C: a species comparison

    Cryobiology

    (1988)
  • T.F. Janezic

    Then and now: 25 years at the Ljubljana Burns Unit skin bank

    Burns

    (1999)
  • T.L. Wachtel et al.

    Viability of frozen allografts

    Am J Surg

    (1979)
  • C.D. Richters et al.

    Morphology of glycerol-preserved human cadaver skin

    Burns

    (1996)
  • S. Franchelli et al.

    In vitro antimicrobial effects of fresh split skin, homologous-cultured epithelium and porcine split skin grafts for wound coverage

    Burns

    (1992)
  • M. Mathur et al.

    Microbiological assessment of cadaver skin grafts received in a Skin Bank

    Burns

    (2009)
  • J.A. Clarke

    HIV transmission and skin grafts

    Lancet

    (1987)
  • V.S. Saegeman et al.

    Short- and long-term bacterial inhibiting effect of high concentrations of glycerol used in the preservation of skin allografts

    Burns

    (2008)
  • L. Marshall et al.

    Effect of glycerol on intracellular virus survival: implications for the clinical use of glycerol-preserved cadaver skin

    Burns

    (1995)
  • J. van Baare et al.

    Virucidal effect of glycerol as used in donor skin preservation

    Burns

    (1994)
  • M.J. Hoekstra et al.

    History of the Euro Skin Bank: the innovation of preservation technologies

    Burns

    (1994)
  • C.D. Richters et al.

    Immunology of skin transplantation

    Clin Dermatol

    (2005)
  • L.K. Branski et al.

    Amnion in the treatment of pediatric partial-thickness facial burns

    Burns

    (2008)
  • J.J. Naoum et al.

    The use of homograft compared to topical antimicrobial therapy in the treatment of second-degree burns of more than 40% total body surface area

    Burns

    (2004)
  • A.B. Walker et al.

    Use of fresh amnion as a burn dressing

    J Pediatr Surg

    (1977)
  • A. Eldad et al.

    Cryopreserved cadaveric allografts for treatment of unexcised partial thickness flame burns: clinical experience with 12 patients

    Burns

    (1997)
  • R.E. Horch et al.

    Treatment of second degree facial burns with allografts – preliminary results

    Burns

    (2005)
  • A.F. Vloemans et al.

    A randomised clinical trial comparing a hydrocolloid-derived dressing and glycerol preserved allograft skin in the management of partial thickness burns

    Burns

    (2003)
  • M.H. Hermans

    Clinical experience with glycerol-preserved donor skin treatment in partial thickness burns

    Burns Including Thermal Inj

    (1989)
  • T.A. Brans et al.

    Long-term results of treatment of scalds in children with glycerol-preserved allografts

    Burns

    (1994)
  • R. Peeters et al.

    Use of glycerolized cadaver skin for the treatment of scalds in children

    Burns

    (1994)
  • P. Leicht et al.

    Allograft vs. exposure in the treatment of scalds – a prospective randomized controlled clinical study

    Burns Including Thermal Inj

    (1989)
  • R. Singh et al.

    Microbiological safety and clinical efficacy of radiation sterilized amniotic membranes for treatment of second-degree burns

    Burns

    (2007)
  • C.P. Sawhney

    Amniotic membrane as a biological dressing in the management of burns

    Burns

    (1989)
  • E. Bujang-Safawi et al.

    Dried irradiated human amniotic membrane as a biological dressing for facial burns – a 7-year case series

    Burns

    (2010)
  • J. Pigeon

    Treatment of second-degree burns with amniotic membranes

    Can Med Assoc J

    (1960)
  • C.P. Artz et al.

    Postmortem skin homografts in the treatment of extensive burns

    AMA Arch Surg

    (1955)
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