Is Sterile Better Than Aseptic? Comparing the Microbiology of Acellular Dermal Matrices

Sourcing and development of tissue for transplantation in reconstructive surgery: A narrative review

The wealth of allogeneic and xenogeneic tissue products available to plastic and reconstructive surgeons has allowed for the development of novel surgical solutions to challenging clinical problems, often obviating the need to inflict donor site morbidity. Allogeneic tissue used for reconstructive surgery enters the tissue industry through whole body donation or reproductive tissue donation and has been regulated by the FDA as human cells, tissues, and cellular and tissue-based products (HCT/Ps) since 1997. Tissue banks offering allogeneic tissue can also undergo voluntary regulation by the American Association of Tissue Banks (AATB). Tissue prepared for transplantation is sterilized and can be processed into soft tissue or bone allografts for use in surgical reconstruction, whereas non-transplant tissue is prepared for clinical training and drug, medical device, and translational research. Xenogeneic tissue, which is most often derived from porcine or bovine sources, is also commercially available and is subject to strict regulations for animal breeding and screening for infectious diseases. Although xenogeneic products have historically been decellularized for use as non-immunogenic tissue products, recent advances in gene editing have opened the door to xenograft organ transplants into human patients. Herein, we describe an overview of the modern sourcing, regulation, processing, and applications of tissue products relevant to the field of plastic and reconstructive surgery.

Clinical applications of acellular dermal matrices: A review

INTRODUCTION

The extracellular matrix (ECM) plays an integral role in wound healing. It provides both structure and growth factors that allow for the organised cell proliferation. Large or complex tissue defects may compromise host ECM, creating an environment that is unfavourable for the recovery of anatomical function and appearance. Acellular dermal matrices (ADMs) have been developed from a variety of sources, including human (HADM), porcine (PADM) and bovine (BADM), with multiple different processing protocols. The objective of this report is to provide an overview of current literature assessing the clinical utility of ADMs across a broad spectrum of applications.

METHODS

PubMed, MEDLINE, EMBASE, Scopus, Cochrane and Web of Science were searched using keywords 'acellular dermal matrix', 'acellular dermal matrices' and brand names for commercially available ADMs. Our search was limited to English language articles published from 1999 to 2020 and focused on clinical data.

RESULTS

A total of 2443 records underwent screening. After removing non-clinical studies and correspondence, 222 were assessed for eligibility. Of these, 170 were included in our synthesis of the literature. While the earliest ADMs were used in severe burn injuries, usage has expanded to a number of surgical subspecialties and procedures, including orthopaedic surgery (e.g. tendon and ligament reconstructions), otolaryngology, oral surgery (e.g. treating gingival recession), abdominal wall surgery (e.g. hernia repair), plastic surgery (e.g. breast reconstruction and penile augmentation), and chronic wounds (e.g. diabetic ulcers).

CONCLUSION

Our understanding of ADM's clinical utility continues to evolve. More research is needed to determine which ADM has the best outcomes for each clinical scenario.

LAY SUMMARY

Large or complex wounds present unique reconstructive and healing challenges. In normal healing, the extracellular matrix (ECM) provides both structural and growth factors that allow tissue to regenerate in an organised fashion to close the wound. In difficult or large soft-tissue defects, however, the ECM is often compromised. Acellular dermal matrix (ADM) products have been developed to mimic the benefits of host ECM, allowing for improved outcomes in a variety of clinical scenarios. This review summarises the current clinical evidence regarding commercially available ADMs in a wide variety of clinical contexts.

From Salvage to Prevention: A Single-Surgeon Experience with Acellular Dermal Matrix and Infection in Prepectoral Breast Reconstruction

BACKGROUND

Increasing amounts of acellular dermal matrix are being used with the adoption of prepectoral breast reconstruction. Postoperative infection remains a challenge in breast reconstruction, and the contribution of acellular dermal matrix type, processing, and sterility assurance level to risk of complications in prepectoral reconstruction is not well studied.

METHODS

The authors performed a retrospective review of patients who underwent immediate prepectoral breast reconstruction from February of 2017 to July of 2020. Because of an increase in the rate of infection, the drain protocol was changed and acellular dermal matrix type was switched from AlloDerm (sterility assurance level, 10-3) to DermACELL (sterility assurance level, 10-6) in January of 2019. Demographic and surgical variables were collected, in addition to details regarding development and management of infection.

RESULTS

Despite higher rates of direct-to-implant reconstruction and bilateral procedures and increased implant volumes, the rate of infection was significantly lower in patients who received DermACELL instead of AlloDerm [two of 38 (5.3 percent) versus 11 of 41 (26.8 percent); p = 0.014]. Drain duration was slightly longer in the DermACELL group, consistent with the change in drain protocol. Baseline demographic and clinical characteristics remained similar between the two groups.

CONCLUSIONS

With increased reliance on large amounts of acellular dermal matrix for prepectoral breast reconstruction, it directly follows that the properties of acellular dermal matrix with respect to incorporation, sterility, and implant support are that much more important to consider. There have been few studies comparing different types of acellular dermal matrix in prepectoral breast reconstruction, and further research is required to determine the contribution of acellular dermal matrix type and processing techniques to development of postoperative infection.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Comparison of irradiated and non-irradiated acellular dermal matrices in breast reconstruction under radiotherapy

Background

Acellular dermal matrices (ADMs) have become an essential material for implant-based breast reconstruction. No previous studies have evaluated the effects of sterility of ADM under conditions of radiation. This study compared sterile (irradiated) and aseptic (non-irradiated) ADMs to determine which would better endure radiotherapy.

Methods

Eighteen male Balb/C mice were assigned to the control group with no irradiation (group 1) or one of two other groups with a radiation intensity of 10 Gy (group 2) or 20 Gy (group 3). Both sterile and aseptic ADMs were inserted into the back of each mouse. The residual volume of the ADM (measured using three-dimensional photography), cell incorporation, α-smooth muscle actin expression, and connective tissue growth factor expression were evaluated. The thickness and CD3 expression of the skin were measured 4 and 8 weeks after radiation.

Results

In groups 2 and 3, irradiated ADMs had a significantly larger residual volume than the non-irradiated ADMs after 8 weeks (P<0.05). No significant differences were found in cell incorporation and the amount of fibrosis between irradiated and non-irradiated ADMs. The skin was significantly thicker in the non-irradiated ADMs than in the irradiated ADMs in group 3 (P<0.05). CD3 staining showed significantly fewer inflammatory cells in the skin of irradiated ADMs than in non-irradiated ADMs in all three groups after 4 and 8 weeks (P<0.05).

Conclusions

Under radiation exposure, irradiated ADMs were more durable, with less volume decrease and less deposition of collagen fibers and inflammatory reactions in the skin than in non-irradiated ADMs.

Intraoperative Autoderm Decontamination for Use in Immediate Single-stage Direct-to-implant Breast Reconstruction

Acellular dermal matrix (ADM) in direct-to-implant breast cancer reconstruction is the standard of care due to superior cosmetic results and decreased capsular contracture, but can be cost prohibitive. Although more economical, using patient’s own dermis (“Autoderm”) instead of ADM has undescribed sterility. Sterility is essential, as bacterial contamination may cause infection and capsular contraction. This study aimed to determine the sterility and optimal decontamination protocol of Autoderm.

Acellular Dermal Matrix Sterility: Does It Affect Microbial and Clinical Outcomes Following Implantation?

The use of acellular dermal matrices (ADMs) in breast reconstruction is a controversial topic. Recent literature has investigated the effects of ADM sterilization on infectious complications, although with varying conclusions. Previous work by our group showed no difference between aseptic and sterilized products immediately out of the package. In this study, we investigate the microbiologic profiles of these agents after implantation.

AlloDerm RTU Integration and Clinical Outcomes When Used for Reconstructive Breast Surgery

Background:

AlloDerm Ready To Use (RTU) is a sterile version of AlloDerm regenerative tissue matrix, developed in response to concerns regarding the potential risk of infectious complications with the latter aseptic matrix. Clinical data on AlloDerm RTU use is, however, limited, particularly with respect to histologic evidence of graft integration and clinical outcomes.

Methods:

Consecutive patients who underwent tissue-expander/implant reconstruction with the use of AlloDerm RTU from March 2011 to September 2012 were included in this analysis. Biopsies of AlloDerm RTU/capsule interface were obtained at the time of expander/implant exchange and evaluated for evidence of cellularization, vascularization, and inflammatory reaction. Data on postoperative complications were retrieved from patient records.

Results:

A total of 116 biopsy specimens from 68 patients were obtained. At biopsy, on visual inspection, nearly all grafts were fully integrated within the host tissue. Histologically, graft specimens demonstrated mild-to-moderate neovascularization and cellular repopulation with no inflammatory cells. All patients were followed for 5 years postoperatively. Short-term postoperative complications of skin necrosis, seroma, and infection occurred in 10.3%, 4.3%, and 2.6% of reconstructions, respectively. Capsular contracture (grade 3) was the only long-term complication (5.2%). Rates of short- and long-term complications are similar to those observed in our previous experience with AlloDerm reconstructive tissue matrix.

Conclusions:

AlloDerm RTU used in breast reconstructive surgery fully integrates and incorporates into host tissue. There were no unexpected safety concerns with its use at short-term or at long-term, at least up to 5 years of follow-up.

A Microbiological and Ultrastructural Comparison of Aseptic versus Sterile Acellular Dermal Matrix as a Reconstructive Material and a Scaffold for Stem Cell Ingrowth

BACKGROUND

Recent data suggest an increased risk for infection when acellular dermal matrix is used in breast reconstruction. This may be because some acellular dermal matrices are actually not terminally sterilized but are instead "aseptically processed." This study evaluates aseptic and sterile matrices for evidence of bacterial contamination and whether or not terminal sterilization affects matrix collagen architecture and stem cell ingrowth.

METHODS

Five separate samples of 14 different matrices were analyzed by fluorescent in situ hybridization using a bacterial DNA probe to detect bacterial DNA on the matrices. Separate samples were incubated for bacteria, acid-fast bacilli, and fungi for 2 to 6 weeks to detect living organisms. The impact of terminal sterilization on the collagen network and stem cell ingrowth on the matrices was then assessed.

RESULTS

Traces of bacterial DNA were encountered on all matrices, with more bacteria in the aseptic group compared with the sterile group (3.4 versus 1.6; p = 0.003). The number of positive cultures was the same between groups (3.8 percent). Electron microscopy demonstrated decreased collagen organization in the sterile group. Stem cell seeding on the matrices displayed a wide variation of cellular ingrowth between matrices, with no difference between aseptic and sterile groups (p = 0.2).

CONCLUSIONS

Although there was more evidence of prior bacterial contamination on aseptically processed matrices compared with sterile matrices; clinical cultures did not differ between groups. Terminal sterilization does not appear to affect stem cell ingrowth but may come at the cost of damaging the collagen network.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Optimizing Outcomes of Postmastectomy Breast Reconstruction With Acellular Dermal Matrix: A Review of Recent Clinical Data

Background: This article reports on the current use of acellular dermal matrix in breast reconstruction. Methods: A literature review of articles on acellular dermal matrix in breast reconstruction from January 1, 2010, through December 20, 2016, was performed and analyzed for trends in acellular dermal matrix use and differences between commonly used acellular dermal matrixes. Findings: Clinical findings varied but include improved cosmesis and more 1-stage reconstructions using acellular dermal matrix. Superiority of sterile versus aseptic acellular dermal matrixes was noted, and the increased incidence of red breast syndrome with AlloDerm was significant. The cost-effectiveness of acellular dermal matrix use despite increased upfront costs was also highlighted. Finally, the article emphasizes the importance of well-vascularized mastectomy flaps and the use of indocyanine green angiography as an adjunct in immediate reconstruction with acellular dermal matrix.