Clinical Efficacy of Acellular Dermal Matrix Paste in Treating Diabetic Foot Ulcers

Introduction. Diabetic foot ulcers (DFUs) are slow to heal because of poor tissue vascularity and regenerative capacity, among various factors. Objective. In this study, the authors evaluate the efficacy of applying a paste formulation of acellular dermal matrix (ADM) to DFUs. Materials and Methods. Patients with Wagner grade 2 or 3 DFUs (N = 49) received either ADM paste (treatment group; n = 23) or conventional foam dressing (control group; n = 26). All chronic wounds were debrided and irrigated in an attempt to control infection. After paste application, mild compaction was undergone to fill ulcer cavities, and foam dressings were used to cover the surface to absorb any discharge. All DFUs were analyzed with regard to ulcer area, depth, progression, healing rate, and duration to complete healing. Results. At the 60-day primary outcome mark, 56.52% (13/23) of the DFUs in the treatment group were healed, compared with 23.08% (6/26) of DFUs in the control group. Mean rates of wound area resolution in the treatment and control groups were 74.17% ± 30.84% and 51.87% ± 32.81%, respectively (P < .05), with mean times to heal (within 60 days) of 13.54 ± 9.18 days and 21.5 ± 11.98 days, respectively (P < .05). There were no serious adverse events in either group, and no complications related to ADM paste application. Conclusions. The ADM paste effectively enhanced tissue regeneration, shortening ulcer duration and preventing associated complications, while eliminating the need for supplemental ulcer management procedures. The paste formulation of ADM provides a matrix for tissue ingrowth, promoting the healing of DFUs.

Poor vascularity and inadequate tissue matrix often plague the management of diabetic ulcers, among various factors. More than 150 million people worldwide suffer from diabetes, and every patient with diabetes is at risk of developing a diabetic foot ulcer (DFU) with varying degrees, and more than 15% will actually develop such ulcers.¹ Among the diverse treatments used to manage DFUs, methods traditionally employed include rigorous dressing changes with cautious observation, debridement of necrotic tissue, infection control, and reduction of pressure on the diabetic foot.^2-4 Lower extremity revascularization is also a consideration in some instances.⁵ If treatments fall short at critical times, these nonhealing, chronic wounds may lead to foot amputations and alter a patient’s quality of life.⁶

Recent studies have explored more effective wound dressings and tissue engineering techniques, such as vacuum-assisted closure, adipose-derived stem cell use, and allogenic or xenogenic material applications.^4,7,8 Similarly, clinical trials have investigated the efficacy of acellular dermal matrix (ADM) in treating DFUs.^2,9 Acellular dermal matrix is a cutaneous derivative incorporating collagens, elastin, glycosaminoglycans, and hyaluronic acids as structural elements. It has been decellularized to limit immune triggers and facilitate host-cell infiltration. This matrix serves as a reservoir of growth factors, such as vascular endothelial growth factor and fibroblast growth factor, for modulating cellular responses, and its structural fortification protects chronic open wounds, preventing deeper tissues from desiccation.^2,10 Clinical studies have already documented the safety and efficacy of ADM in chronic wound healing.^9,11 In addition, paste formulations of ADM easily can be introduced into geometric or tunnel-type ulcers without damaging adjacent tissues. When combined with gelatin, micronized ADM shows semi-fluidic characteristics.

In this study, the authors evaluated the safety and efficacy of ADM paste in treating patients with DFUs. Area and depth of the wounds were monitored over time, analyzing their progression, healing rates, and durations to complete healing. 

The authors retrospectively reviewed the medical records of patients with DFUs. Inclusion criteria involved patients with DFUs that were treated between August 2015 and January 2018. They received wound management using either ADM paste or conventional foam dressing method. The study protocol conformed to the ethical guidelines of the Declaration of Helsinki, as reflected in the approval by the Konkuk University School of Medicine (Seoul, South Korea) human research review committee. The study was approved by the Institutional Review Board of Konkuk University School of Medicine (KUH 1280110).

The authors comprehensively reviewed data from 86 consecutive patients who were potential study candidates. Patients afflicted with chronic DFUs characterized as Wagner grade 2 or 3 of at least 4 weeks' duration were included in the study.^12,13 All patients had been diagnosed with type 1 or type 2 diabetes mellitus.¹⁴ Adequate renal function (serum creatinine < 3.0 mg/dL) and a hemoglobin (Hb) A_1c level less than 9% were required for inclusion in the study. Every subject underwent computed tomography angiography to confirm patency of the pertinent arterial vessels. Doppler arterial waveforms provided adjunctive evidence, marked by triphasic or biphasic patterns at the ankle level of the extremity with the DFU. Results of serial wound cultures indicated no definite bacterial growth or only controlled flora (ie, few colony-forming units). There were 31 patients with ischemic DFUs and 6 patients with uncontrolled infection excluded. The remaining 49 patients were classified into 2 groups: treatment group (ADM paste, n = 23) and control group (conventional foam dressing, n = 26). The management technique between the 2 methods was selected in accordance with permuted-block randomization (block size 4). A study author (ML) generated the random sequence using Excel (Microsoft Corporation, Redmond, WA). The allocation sequence was utilized to adequately distribute the dressing methods. The patients were blinded until the allocation; nonetheless, further blinding was not available since the dressing method exhibited different materials in procedures. The selection did not depend on patients’ demographics and wound sites. The inclusion and exclusion criteria for study eligibility are summarized in Table 1.

First, the DFUs were prepared using careful debridement and vigorous irrigation, before the ADM paste was applied (CG paste; CG Bio, Seongnam-si, Gyeonggi-do, South Korea) in the treatment group only (Figure 1). The amount of ADM paste needed depended on ulcer size and depth. Light surface compaction was used to avoid dead space, and a nonadhesive foam dressing was applied to the surface for containment (Figure 2). In the control group, treatment solely consisted of ulcer bed preparation, overlaying the ulcer with the same type of foam dressing. Dressings were changed every 3 to 4 days. To redistribute pressure on the plantar surface of the foot, the authors used a removable cast walker specifically designed to eliminate pressure on the DFU. 

The area and depth of the ulcers were measured at baseline (before initiating wound management) and at each dressing change. A single study author (DJ), blinded to the treatment protocol, conducted all measurements. The measurements were performed twice at each visit, and the mean was used for data analysis. The maximum length, width, and depth of each wound were determined using a sterilized ruler. Ulcer area was calculated as length multiplied by width multiplied by 1/4 π.⁷ Full tissue ingrowth and reepithelialization without discharge constituted complete healing. Ulcer evaluations also were recorded on days 20, 40, and 60 after ADM paste application. 

The t test for unpaired samples was used to compare continuous variables between the treatment and control groups. Pearson’s chi-square test was used to compare categorical variables, including the rates of wound healing. Probabilities of healing were generated via Kaplan-Meier method. All data analyses were performed with standard software (SPSS Windows v20.0; IBM Corp, Armonk, NY). The statistical significance was set at P < .05, expressing all data as mean ± standard deviation. 

For all 49 patients (treatment group: n = 23; control group: n = 26), the following demographic variables were recorded: age; gender; body mass index (BMI); serum Hb, HbA_1c, and albumin levels; and ulcer location. The treatment and control groups were comparable for all variables (Table 2).

Clinical ulcer measurements and outcomes included area and depth of DFUs, follow-up period, and time to complete healing. Ulcer severity (ie, Wagner classification) appeared comparable in both groups (Table 3). In the treatment group, initial ulcer measurements (area: 13.81 cm² ± 19.30 cm²; depth: 1.03 cm ± 1.23 cm) declined significantly over the course of study (final values; area: 6.87 cm² ± 10.52 cm²; depth: 0.07 cm ± 0.13 cm; P < .05) (Figures 3, 4). In the control group, initial ulcer dimensions were comparatively less extensive (area: 7.97 cm² ± 10.00 cm²; depth: 0.93 cm ± 0.63 cm), but also declined significantly (final values; area: 5.90 cm² ± 8.31 cm²; depth: 0.57 cm ± 0.67 cm; P < .05) (Table 3). However, the rates of ulcer resolution in the treatment (area: 74.17% ± 30.84%; depth: 87.18% ± 18.9%) and control (area: 51.87% ± 32.81%; depth: 45.98% ± 32.89%) groups differed significantly (P < .05) (Table 4). At the end of the follow-up period, 13 of 23 ADM paste-treated patients (56.52%) showed complete healing, whereas only 6 of 26 control patients (23.08%) achieved complete healing (P < .05) (Table 5). The corresponding mean follow-up intervals until complete healing were 33.74 ± 24.51 days and 51.12 ± 17.39 days, representing a significant difference (P < .05). The mean time to complete healing in the treatment group (13.54 ± 9.18 days) was significantly shorter than that of the control group (21.5 ± 11.98 days, P < .05) (Table 3). Further, the mean number of ADM paste applications was 5.74 ± 3.17 in the treatment group overall, and the mean number of applications was 3.68 ± 1.25 in completely healed ulcers. 

The authors monitored ulcer healing for 60 days to assess healing probability (via Kaplan-Meier estimates). In the per-protocol population, ADM paste application demonstrated significantly greater ulcer healing probability than conventional care within the 60-day period (Figure 5).

Diabetic foot ulcers are characterized by chronicity and relapse.¹⁵ They are often difficult to heal completely and may lead to foot or more proximal limb amputations.¹⁶ The clinical challenges posed by DFUs have spawned supplemental techniques to overcome inherent vascular and regenerative deficiencies. A wound lasting 4 weeks or more qualifies as chronic, which is a critical factor because infection, biofilm formation, and underlying tissue desiccation may exacerbate conditions and hamper the healing process.¹⁷

Biologic dressings have shown promise in the setting of DFUs.^2,16,18 In a randomized clinical trial,² a single application of ADM paste brought improvement, reducing the area and depth of the ulcers. Ulcer healing also progressed faster by applying ADM in sheets (vs. conventional dressings) to chronic, full-thickness wounds of the lower extremities.¹⁹ A recent clinical study⁹ of 80 patients validated the efficacy of acellular reticular allogenic human dermis in the management of DFUs.

Herein, the authors tested a paste formulation of ADM that aided in the healing of DFUs over a 60-day period.^2,11,19 This paste is a mixture of micronized ADM and a gelatin solution. The resultant semi-fluidic product sustains the benefits of ADM during the healing process. Upon manual pressure, it flows readily from a syringe yet remains structurally cohesive. Such unique features enable thorough coverage of ulcers that vary in shape and depth, including those with geometric or tunneling architectures.²⁰ Conventional sheets of ADMs are appropriate for flat ulcers but are not amenable to convoluted defects. The ADM sheets also must be soaked prior to use for proper hydration, whereas the paste formulation is immediately available at outpatient clinics, with no such restrictions.²¹

The regenerative properties of micronized ADM, namely host-cell infiltration, structural support, and cell-to-cell signaling, are a matter of record as well. Acellular dermal matrix contains collagen and elastin to instill tensile strength and elasticity, angiogenesis-inducing proteoglycans, and laminin, a binder of connective tissue.^8,9,22

In comparative analysis, ADM paste-treated patients (vs. controls) demonstrated a significantly faster rate of healing, as indicated by ulcer area and depth. Declines in these objective parameters underscored the utility of matrix use in promoting tissue regeneration. In fact, these findings occurred despite the mean initial wound area of the treatment group (13.81 cm² ± 19.30 cm²) exceeding that of the control group (7.97 cm² ± 10.00 cm²; P < .05). Broader ulcer areas often do not bode well, because the central regions of ulcers are the slowest to heal.^23,24 However, the final areas in treatment and control groups were comparable, illustrating the dynamic role of ADM paste therapy in sizable ulcers. Initial ulcer depths in these groups did not differ significantly, but the final measurement of the treatment group (0.07 cm ± 0.13 cm) again surpassed the control group (0.57 cm ± 0.67 cm; P < .05) in terms of decremental resolution, signaling accelerated tissue ingrowth (Table 3, Table 4).

In the present study, the proportion of healed ulcers at 60 days also differed significantly by group (treatment: 56.52%, 13/23; control: 23.08%, 6/26; P < .05), confirming the merit of ADM and corroborating outcomes of another recent trial¹ using ADM sheets. That trial¹ reported a 65% (13/20) rate of healing at 6 weeks for ADM-treated DFUs, compared with a 5% (1/20) rate of healing with standard care. Likewise, in assessing the efficacy of bovine acellular flowable matrix, a remarkable advantage emerged for the matrix group (86.95% fully healed at 6 weeks) compared with controls (52.17%).²⁵ Of note, the seemingly discrepant rates of cellular migration among various ADM formulations are attributable to existing inflammatory cell densities responsible for matrix remodeling and revascularization.²⁶

In the present treatment group, the mean time to complete ulcer healing was 13.54 ± 9.18 days compared with 21.5 ± 11.98 days in controls (P < .05). Accelerated ulcer healing is of major importance because the poor vascularity associated with comorbid conditions renders the healing process in diabetic ulcers unpredictable. In addition, there are treatment costs to consider. Compared with other wound management products, ADM paste is a cost-effective alternative as well as more convenient due to the outpatient basis. The mean number of serial ADM paste applications was 5.74 ± 3.17 in the treatment group overall, but in completely healed ulcers, that figure was only 3.68 ± 1.25. Currently, an application of 1 mL to 2 mL of ADM paste costs $100 to $150 and can be conveniently undertaken on an outpatient basis, as opposed to the stringent preparation (and potential for bacterial contamination) involved in using ADM sheets.

Kaplan-Meier estimates of the time to complete healing were plotted throughout the study period and showed significantly higher healing probability at day 60 in the treatment (vs. control) group (P < .05). This finding attests to the efficacy of ADM paste in achieving sequential progressive healing. Furthermore, accelerated healing took place within 30 days, which is advantageous in the poorly vascularized diabetic ulcer environment. Thus, the data reported herein support this ulcer management strategy in patients with challenging DFUs.

As previously described, ADM paste was pushed into ulcer crevices and tunnels to avoid dead space and ensure adequate matrix for cellular migration and subsequent cell-to-cell contact. Apart from the present investigation, the authors have used negative pressure for this purpose in recalcitrant, poorly vascularized wounds. Past accounts suggest negative pressure wound therapy (NPWT) enhances granulation tissue proliferation.^27,28 The authors’ research into joint use of ADM paste and NPWT is ongoing.

The limitations of this study include a lack of histologic support detailing the microscopic aspects of repair. In earlier observations, micronized ADM appears to support many cellular constituents of tissue regeneration, including fibroblasts, macrophages, plasma cells, adipocytes, and mast cells. The complex provides a loose meshwork of collagen and elastic fibers, serving as a scaffold for vascular ingrowth. Another issue is that of competing ADM formulations (paste vs. sheets), which were not directly compared on an objective basis. However, prior analyses of various ADM preparations and fabrication methods seem to validate this particular indication for ADM paste. Finally, the authors’ protocol clearly bears further scrutiny, given the small number of patients assigned to each group.

The results of this study demonstrate the healing effects of ADM paste in Wagner grade 2 or 3 DFUs. As a mixture of micronized ADM and gelatin, this paste readily conforms to geometric and tunneling ulcers, and the initial acceleration of healing documented within 30 days may be particularly advantageous in poorly vascularized diabetic ulcers. Further clinical testing and follow-up monitoring are required to confirm its promise in managing hard-to-heal DFUs

Authors: Myungchul Lee, MD, PhD; Dongkeun Jun, MD; Hyungon Choi, MD, PhD; Jeenam Kim, MD, PhD; and Donghyeok Shin, MD, PhD

Affiliation: Department of Plastic and Reconstructive Surgery, Konkuk University School of Medicine, Seoul, South Korea

Correspondence: Donghyeok Shin, MD, PhD, Professor, Department of Plastic and Reconstructive Surgery, Konkuk University School of Medicine, 120-1 Neungdong-ro, Gwangjin-gu, Seoul 05030, South Korea; sdhplastic@kuh.ac.kr 

Disclosure: The authors disclose no financial or other conflicts of interest.