Amniotic Suspension Allograft and Fetal Bovine Acellular Dermal Matrix to Treat Complex, Acute, Full-thickness Wounds: A Retrospective Analysis of Safety and Treatment Efficacy

Introduction. Comorbidities; inadequate vascularity; exposure of bones, tendons, or other avascular structures; and loss or removal of significant tissue volume all complicate the clinical treatment of patients with large, acute wounds. A number of amniotic tissue products are currently available for wound healing and other applications; one of these is a human amniotic suspension allograft (ASA) consisting of particulated human amniotic membrane and cells from the amniotic fluid from the same human donor. Objective. In this study, the use of ASA with a fetal-derived bovine acellular dermal matrix to promote the healing of large, acute, full-thickness wounds is evaluated. The authors herein hypothesize treatment with ASA may allow for the healing of these wounds. Materials and Methods. This study consisted of a chart review of 33 patients, with an average age of 42.2 years, and large acute wounds that were treated with a fetal-derived bovine acellular dermal matrix adsorbed with ASA. To the best of the authors’ knowledge, this is the first study to date to investigate the usefulness of ASA in wound healing for large, complex, acute wounds. Results. In this study, 30 of 33 patients were confirmed as fully healed, and 3 patients were lost to follow-up. The average wound size was 537.4 cm², and the average time to split-thickness skin grafting (STSG) was 30.5 days, with an average time of 6.8 days until at least 95% graft take was achieved. Of the patient population studied, 45.5% had 1 or more significant comorbidities, 30.3% had wounds larger than 500 cm², and 39.4% had exposed bone or tendon. Conclusions. In a small but challenging population including a high number of patients with comorbidities and exposed bone or tendon, it was found that ASA delivery, along with a dermal matrix, was successful in treating large, complex, acute wounds.

Appropriate selection of the proper treatment modality can be confusing and challenging in the field of wound care. Current estimates for total Medicare spending for the management of all wound types range from $28.1 to $96.8 billion in annual health care-associated costs.¹ Despite a dearth of clinical trials to guide therapy, a lack of consensus on a treatment algorithm for complex, acute wounds remains. For example, a meta-review² found that after analyzing 99 systematic reviews regarding wound healing, there were multiple promising interventions but minimal consistency across wound types and throughout the literature.

For chronic wounds, some of the commonly employed techniques utilize hydrogels and foams to decrease moisture imbalance.³ Based on a 2013 meta-analysis of 5 studies with 446 patients,⁴ hydrogels demonstrated significantly greater healing in patients with diabetic foot ulcers when compared with standard dressings or no dressing at all. In addition, there are more advanced biological treatments, including topical treatments with enzymes, growth factors, and cell-based products, to modulate the wound environment to promote healing.⁵ In a recent review and meta-analysis,⁵ more than 40 trials with over 1700 patients presented evidence that active wound dressings were more effective in comparison with traditional dressing techniques but required more randomized trials for additional support. 

Although these techniques are well-suited for small wounds, larger wounds (>500 cm²) often require additional and/or more advanced treatment steps. There are difficulties in treating large, complex, acute wounds with advanced wound care products, as the larger wound size and necessity for multiple treatments often can preclude many of these grafts. Skin autografting is considered the gold standard mainstay for complex wounds with extensive dermal tissue loss and damage^6,7; however, the donor site necessary for creating a large graft causes its own complications, including donor site morbidity, pain, and scarring.^6,7 Large wounds with defects in vascularity may be treated with local or free tissue flap transfers, but proper healing is subject to prolonged immobilization and control of comorbidities. Comorbidities including diabetes, chronic obstructive pulmonary disease, and smoking increase the difficulty of administering treatment and reduce the success rate of flaps, highlighting the need for alternative treatment modalities. An alternative that has been employed in some cases is the use of a dermal substitute; these grafts have been used to alleviate the need for full-thickness grafting by promoting neodermis to provide coverage of underlying tissue, including bone, tendons, and other structures.^8-15 As a second step, a split-thickness autograft is often placed. 

Many of the currently available dermal matrix products are scaffolds taken from a collagen source and used as a temporary extracellular matrix. A fetal-derived bovine acellular dermal matrix (FBADM; PriMatrix Dermal Repair Scaffold; Integra LifeSciences Corporation, Plainsboro, NJ) has been used in partial- and full-thickness wounds and shown to significantly accelerate healing compared with standard therapies,^16,17 including in patients who were not ideal candidates for flap coverage. 

Tissues derived from placental membranes have been utilized as an adjunct to chronic wound healing by many groups.^18,19 Amniotic suspension allograft (ASA; NuCel; Organogenesis Inc, Canton, MA) consists of growth factors and cells from the amniotic fluid, along with particulated amniotic membrane in a cryopreserved suspension. Placental-derived tissue has been reported to be nonimmunogenic, anti-inflammatory, and have antibacterial properties.^20–25 These tissues have been shown to promote proliferation and migration of cells important to wound healing, including fibroblasts, keratinocytes, and endothelial cells.^26,27 Amniotic tissue also has been reported^28–34 to reduce scar tissue formation and pain at the site of application and protect against infection by serving as a biological barrier. In addition, amniotic tissues have demonstrated improvements in aesthetic results and decreased hypertrophic scarring when compared with conventional dressings in split-thickness skin graft (STSG) donor sites.³⁵ 

While most previous works examining alternatives to traditional wound healing techniques used small wounds in patients with less complex comorbidities, this study aimed to investigate the safety and efficacy of ASA as an adjunct to FBADM application within a complex patient population undergoing treatment for various large acute wounds. The authors hypothesized the physiologically relevant growth factors and cytokines released from the ASA product would facilitate healing of complex wounds on a larger scale.

Study design

A retrospective, single-arm, single-center chart review was conducted to elucidate the safety and efficacy of ASA-enriched FBADM in the treatment of patients with surgically debrided, full-thickness wounds. This study was approved by the University of Alabama at Birmingham Ethics Committee (Protocol Number: X1407210043). 

All data were electronically collected through a sequential series chart review. Patient demographics and wound characteristics, including etiology, dimensions of the excised areas in which FBADM plus ASA were applied, and location, were recorded. Details on previous treatments, treatment regimens, complications, percent of FBADM assimilation, time to STSG, STSG take, clinical outcomes, and complications related to the procedure also were documented.

Outcome subanalyses were performed for patients with large wounds (> 500 cm²), exposed bone or tendon, and for patients with clinically relevant comorbidities (eg, metabolic syndrome, premorbid vascular dysfunction, tobacco use, recent pressor administration).

Surgical techniques

Wounds were surgically excised to remove necrotic tissue and debris. Excision was performed with standard surgical techniques, including the use of a Weck dermatome or VERSAJET Hydrosurgery System (Smith & Nephew, Fort Worth, TX) depending on the location and type of wound.

Wounds were covered with a temporary xenograft dressing to confirm the wound was free of all necrotic tissue. To cover the xenograft, different types of dressings and wound management techniques were utilized. Typically, 3 to 5 days after the initial excision and temporary dressing placement, the temporary dressing was removed, and the wound was reassessed. If nonviable tissue remained, the process was repeated until the wound was free of necrotic tissue.

The FBADM was cut to shape and rehydrated in sterile, room-temperature saline. The FBADM was meshed at 1.5:1 or 3:1 with a mesher (Zimmer Skin Graft Mesher; Zimmer Biomet, Warsaw, IN) in order to allow for optimal conformity and permit drainage of exudate from the underlying wound bed. Excess saline was removed from the FBADM, and the graft was adsorbed with a mixture of ASA and whole blood (ratio of 1:2). The ASA-soaked FBADM was secured to the wound bed using sutures or staples as appropriate. 

The FBADM plus ASA were covered with a nonadherent dressing (Dermanet Wound Contact Layer; DeRoyal, Powell, TN) to provide protection to the matrix from mechanical forces, as well as to provide an initial bolster to the wound. Negative pressure wound therapy (NPWT) was utilized when clinically possible. If wound size or location prevented NPWT, a petroleum-based product (Xeroform Petroleum Wound Dressing; DeRoyal) was applied directly to the nonadherent dressing and covered with polysporin and/or CUTICERIN Ointment (Smith & Nephew). Secondary dressings other day for the first week and then on an as-needed basis. Typically, sutures and staples were removed 1 week after the FBADM plus ASA application.

During dressing changes, wounds were inspected visually to assess the degree of tissue development. In addition, the occurrence of complications (hematomas, infection, wound dehydration, or maceration) was assessed. Tissue generation was determined by evaluating the neodermis filling through the FBADM. A patient in this dataset required reapplication. For this patient, an excision of the area was performed, and FBADM plus ASA was reapplied following the aforementioned application procedures.

When the wound bed contained robust neodermis, as evidenced by red tissue throughout the FBADM and bleeding after gentle abrasion, STSGs were applied (thickness of 0.008 in–0.012 in). Based on the wound site location, wound size, and amount of skin available for skin grafts, STSGs were meshed (1:1, 1.5:1, or 2:1, depending on the anatomical location) using a dermatome and carrier (Zimmer Bioment Electric Dermatome; Zimmer Biomet). Split-thickness skin grafts were secured to the wound site with staples or sutures. When clinically possible, NPWT was utilized; when not feasible, a bolster dressing with the petroleum-based product and polysporin was used. Visual assessments regarding the level of reepithelialization were assessed at a 2- to 3-day interval.

In total, 33 subjects (8 women, 25 men; mean age, 42.2 ± 17.1 years) were included in the study (Table 1). The average size of full-thickness wounds within the overall cohort was 537.4 cm² ± 1015.1 cm² (Table 1). Average time to STSG was 30.5 ± 14.1 days and an additional 6.8 ± 7.7 days for 95% STSG take; time to complete healing (measured by time to STSG plus time to 95% graft take) was 34.57 ± 12.8 days with complete wound healing observed in 90.9% (30/33) of patients. The remaining 3 patients were lost to follow-up. Interestingly, 2 who demonstrated complete wound healing in this series had previously failed treatments with either a flap and FBADM or FBADM alone. In this case series, there were no study-related complications. 

In this complex population, patients presented for a variety of reasons, including trauma (n = 27), previous wound complications requiring revision (n = 5), and decubitus ulcer post surgery (n = 1). Figure 1 shows a patient presenting with necrotizing fasciitis of the neck. The area was excisionally debrided, and FBADM plus ASA was secured in the wound bed (Figure 1B). At 7 days postapplication of FBADM with robust neodermis, the wound bled upon abrasion (Figure 1C). At 12 days postapplication of FBADM plus ASA, reepithelialization started to occur in some areas (Figure 1D).

In this retrospective review, there were 2 patients (1 woman, 1 man) who did not undergo subsequent STSG due to various factors (Table 2). These patients were 50.5 ± 0.7 years old, with an average wound size of 57 cm² ± 9.9 cm². Both patients had bone or tendon exposure, and their wounds completely healed by 102.5 ± 21.9 days. 

From the patients undergoing placement of FBADM and subsequent STSG, patient subsets were evaluated based on wound size, significant comorbidities, and bone or tendon exposure. There were 10 patients (2 women, 8 men) treated with FBADM plus ASA for wounds larger than or equal to 500 cm² (average, 1795 cm²; Table 3). Within this subpopulation, there were 4 patients with extensive metabolic comorbidities and 2 who were recently treated with pressor therapy. Complete wound healing occurred in 100% (10/10) of these patients, with an average time to STSG of 27.2 ± 9.9 days. An additional 5.1 ± 2.3 days were required for 95% graft take. 

Further stratification of patients with complex presentations included analysis of 17 individuals with extensive comorbidities/recent treatment with pressor therapy (Table 4) and 13 wounds with exposed bone or tendon in 12 patients (Table 5). In this stratification, there were 6 patients with both extensive comorbidities and exposed bone or tendon — 2 of the major obstacles reported to complicate wound healing. Verification of complete wound healing occurred in 88.2% (15/17) of patients with extensive comorbidities and 84.6% (11/13) of patients with exposed bone or tendon, with the remaining patients lost to follow-up. Average time to STSG was 32.1 ± 16.7 days and 31.5 ± 17.0 days for those patients with extensive comorbidities and exposed bone or tendon, respectively. In these same stratifications, time to 95% STSG take was 6.1 ± 5.3 days and 9.4 ± 12.6 days, respectively.

To further showcase this stratification of patients with exposed bone or tendon, Figure 2 shows a patient presenting with an exposed Achilles tendon (about 14 cm in length; Figure 2A). At 7 days postapplication of FBADM plus ASA, the wound area showed complete coverage of the tendon (Figure 2C). At 5 days following STSG, 95% graft take was achieved (Figure 2D). 

This study evaluated the safety and efficacy of ASA as an adjunct to FBADM application for large, complex wounds in a patient population that included a high number of patients with wounds greater than or equal to 500 cm², extensive comorbidities, and exposed bone or tendon structures. Deposition of neodermis was sufficient to proceed with STSG 30.5 ± 14.1 days after the initial application of FBADM plus ASA across the patient population. In this complex population, the authors were successful in treating all wounds without any study-related complications, with the exception of the 3 patients who were lost to follow-up. The results provide strong evidence that the addition of ASA to FBADM may be a safe strategy for healing large, complex wounds. 

The size and cost of placental-derived sheet products may limit utilization for large, complex wounds. In this study, FBADM impregnated with ASA was utilized prior to STSG to create an optimal wound environment for graft incorporation. The data herein support existing works that report fetal bovine matrices^36-41 and NPWT^42-47 may improve wound healing and accelerate healing time.

This work is novel in that ASA in concert with FBADM (and NPWT where appropriate) was evaluated. The mean time to STSG and time to 95% graft take with FBADM plus ASA was 30.5 and 6.8 days, respectively. In this study, average time to healing (from surgical application of FBADM plus ASA through 95% graft take or closure) was reported as 34.6 days for individuals who received STSG. Other studies^37,40,43 have evaluated the use of FBADM in acute wounds; however, direct comparisons are difficult to draw because of the complex nature of these wounds, including differences in severity and sizes, comorbidity status, and varied approaches for closure. Although there are a growing number of clinical studies and case series evaluating placental-derived tissues for wound repair, there is limited published work on ASA in wound repair. In a 2016 published retrospective series,⁴⁸ a cryopreserved ASA was applied to 5 patients with chronic, nonhealing wounds. All 5 patients experienced complete wound closure within 5 to 22 weeks, following 1 to 2 applications. It should be noted, however, that in addition to evaluating chronic wounds, the largest wound evaluated in the case series was 27.0 cm².⁴⁸

In a stratified population of wounds larger than or equal to 500 cm², trends were reported in terms of shorter times to STSG (27.2 vs. 30.5 days) and 95% graft take (5.1 vs. 6.8 days) compared with the full dataset, respectively. It is hypothesized by the authors that these differences are due to duration of hospitalization, resulting in differences in inspection of the wounds (less frequent) and time needed for scheduling STSG procedures. In this study, significant comorbidity stratification was based on serious comorbidities, including metabolic syndrome, premorbid vascular dysfunction, tobacco use, and recent pressor administration; 15 of 17 patients in this stratification went on to complete healing.

While providing an initial opportunity for assessment of the FBADM plus ASA safety and efficacy in complex wound healing, retrospective chart reviews, particularly from a single medical center, have significant limitations. These include a lack of generalizability of the findings to the field at large and a lack of comparative power to standard of care treatment to demonstrate superiority. Although this study was inclusive of a high proportion of complex wounds, with inclusion of patients with clinically significant comorbidities, bone or tendon exposure, and large wounds, future studies should focus on further quantifying the benefit of ASA in a randomized, controlled fashion by studying dermal templates with and without ASA. In addition to evaluating the effects of ASA on healing, longer-term follow-up measuring scarring and range of motion may be appropriate metrics to evaluate.⁴⁹ While statistical analysis was not possible with the dataset presented in this work, due to a lack of comparison groups, future studies could address this issue by inclusion of a control arm and a randomized trial design.

Within the limitations of this single-center, retrospective series, the authors have demonstrated that ASA enrichment of FBADM results in rapid generation of dermal tissue and 95% graft take, resulting in definitive wound closure in a complex population. In addition, there was the completed subset analyses of patients with wounds greater than 500 cm², comorbid patients, and exposed bone or tendon. Furthermore, there were no treatment-related complications reported, which is consistent with previous studies^50,51 that have reported very low ASA-related complication rates. Overall, this study presented promising results, and the surgeons hypothesized the use of ASA to augment FBADM reduced the time to complete healing. Reducing time to closure is an important clinical metric, as it could potentially translate to a reduced risk of infection and significant reduction in the cost of care for patients. 

Authors: Steven Thomas, MD¹; Peter Yen, PA-C¹; Joseph Sclafani, MD²; Joseph Connor, MD³; John McQuilling, PhD⁴; and Katie Culpepper Mowry, PhD⁴

Affiliations: ¹Burn Center, University of Alabama at Birmingham, Birmingham, AL; ²MileStone Research Organization, San Diego, CA; ³Spalding Rehabilitation Hospital, Aurora, CO; and ⁴Organogenesis, Birmingham, AL

Correspondence: Katie Culpepper Mowry, PhD, Director Research and Development, Organogenesis Inc, Surgical and Sports Medicine, 2641 Rocky Ridge Lane, Birmingham, AL 35216; kmowry@organo.com

Disclosure: Drs. McQuilling and Mowry are employees of Organogenesis. Dr. Thomas and Mr. Yen were previous consultants for Organogenesis but not within the last 3 years.