The Use of Acellular Products in Venous Leg Ulcers: A Narrative Review

Advanced age and obesity are both risk factors for venous insufficiency, which often leads to the development of VLUs. VLUs are open lesions that result from poor venous circulation. They are the most common type of chronic wound in the lower extremity.^1,2 While there are no formal clinical registries of VLUs, 1.08% of the US population has been estimated to have VLUs, which significantly affects the quality of life and mobility of these patients.¹ Due to chronic inflammatory signaling and impaired response to wound healing signals in the native tissue, these ulcers and wounds often do not heal and become chronic.³  In addition, all patients with VLUs (Clinical, Etiological, Anatomical, and Pathophysiological [CEAP] status of C6) have lymphatic dysfunction that impairs wound healing and causes high rates of recidivism.⁴ Thus, phlebolymphedema of VLUs is often a cause of VLU closure failure.⁵ 

The growing population of aging Americans in combination with the increased prevalence of obesity has resulted in more cases of venous insufficiency. A 2012 study indicated that approximately 600 000 Americans are diagnosed with VLU each year, with a significant cost burden that ranges from $1.5 billion up to $14.9 billion annually.^6,7 The current SOC for VLUs is compression therapy. Unfortunately, compression therapy is not always successful, with some studies reporting that 35% to 50% of ulcers remain unhealed after 6 months.⁷ Additionally, most VLUs are slow to heal, and have a recurrence rate of up to 70% with a risk of becoming chronic.^8,9 VLUs are often associated with pain, mobility restrictions, and restrictions of activities of daily living, all of which negatively affect patient quality of life.¹⁰ 

Comprehensive VLU evaluation includes the patient’s medical history, physical examination, and noninvasive tests (eg, duplex scanning). Management includes lifestyle changes, medications, and, in severe cases, interventions such as surgery.¹¹ VLU treatment algorithms can be organized into 3 major categories: criteria for referral to a vascular specialist, vascular assessment, and intervention plan. Patients who present with a break in the skin below the knee that has not healed in 2 weeks should be referred to a vascular specialist. Lower extremity assessment should include duplex ultrasound and ankle-brachial index measurements. Noninterventional treatment should include local wound care and compression therapy.¹¹ The Society for Vascular Surgery clinical practice guidelines recommend serial wound measurements, arterial testing, and wound debridement, as well as biopsy for ulcers for which standard treatment is unsuccessful.¹² Interventional treatment options include foam sclerotherapy and endovenous ablation for patients with larger vein insufficiency. One large-scale, multicenter study of 450 patients with VLU found that compared with patients who received compression therapy alone, patients who underwent early endovenous ablation had significantly higher rates of healed ulcers at 24 weeks and longer ulcer-free time after ablation.¹³ Similarly, a multicenter observational study of 76 patients with VLU (80 ulcers) who received foam sclerotherapy found that 53.8% of wounds healed at 12 weeks and remained healed in 88.9% of patients at 12 weeks after wound closure.¹⁴ An RCT of 500 patients with VLU demonstrated reduced ulcer recurrence in patients who received compression with superficial venous surgery as opposed to compression therapy alone.¹⁵ Despite these promising findings, VLU treatment challenges persist. One study found that delayed referral time and delayed time to evaluation in clinic were significant drivers of late VLU evaluation and surgical management.¹⁶ Furthermore, poor compliance both in terms of wound progression monitoring and wound treatment has been reported as a common cause of nonresponse to compression therapy.¹⁷ The service barriers and compliance challenges in VLU management underscore the potential value of adjuncts such as acellular products. 

Acellular products include ADMs, dermal regenerative templates, and placental-derived allografts; more recently, they include fish skin grafts, ECM products, and other synthetic acellular matrices. ADMs originate from cadaveric, allograft, or xenographic skin that is then used as an inert scaffold upon which processes such as reepithelialization, neovascularization, and fibroblast infiltration can occur.¹⁸ In addition to native ECM elements,¹⁹ ADMs include biochemical and structural components such as collagen, elastin, proteoglycans, and laminin to promote tissue healing.²⁰ Initially, ADMs were primarily used in the management of burn wounds to provide wound coverage and prevent infection.^19,21,22 Additionally, ADMs provide a scaffold for burn wound skin renewal and vascularization, both of which accelerate wound healing.^23-25 

The use of ADMs has broadened over the past several decades, with applications in a variety of procedures including reconstructive surgery, cleft palate repair,⁷ post-burn contracture prevention,²⁶ and abdominal hernia repair, in which the use of ADMs has been associated with decreased rates of hernia recurrence.²⁷ Prior to the use of ADMs, large soft tissue defects were managed with autologous skin grafts or flaps.¹⁹ ADMs offer distinct advantages in that they provide a 3-dimensional scaffold that mimics the natural ECM, thus facilitating the regeneration of new tissue without the burden of donor site morbidity. In the case of implant-based reconstruction, ADMs allow host cells to incorporate into the matrix during the healing process, which then provides long-term durability of the implant.²⁰ When used in implant-based breast reconstruction, ADMs improve breast projection, shape, and tissue softness. Additionally, ADMs lower the incidence of breast implant CC, where one review article reported a CC rate of 2.6% with the use of ADM compared to a CC rate of 8.3% to 17.1% without ADM (+Macadam).^28-30 More recently, ADMs have gained traction in the management of nonhealing cutaneous ulcers. In particular, research with the aim of understanding the ability of ADMs to enhance wound healing in DFUs has become an area of significant focus. In the setting of DFUs, ADMs support cell migration and proliferation, and also act as a barrier to protect nonhealing ulcers from bacterial contamination.^31-33 In addition to ADMs, dermal regenerative templates (eg, Integra Life Sciences)³⁴ have been shown to decrease time to wound closure in DFUs and improve outcomes in patients with critical limb ischemia.^35,36 Additionally, placental allografts, which contain ECM proteins and growth factors that assist the healing of chronic vascular ulcers, have been shown to improve wound healing in chronic lower limb VLUs.^37-40 Similarly, ECM products such as OASIS (Smith+Nephew) have demonstrated promise as a wound healing adjunct in the setting of chronic wounds, including DFUs and other full-thickness pressure ulcers.^41-43

Wound bed preparation for acellular product application can be conceptualized using the mnemonic device TIME: tissue debridement/management, infection or inflammation, moisture balance, and edge effect.⁴⁴ The overall goal of wound bed preparation is to create a healing environment that optimally allows for acellular product integration into the wound. Tissue management involves removing any necrotic tissue in order to reduce wound contamination and aid the healing process. Because chronic wounds (eg, VLUs) often are colonized by bacteria, debridement of the existent biofilm at the wound bed is of critical importance. Additionally, it is important to identify the colonization and treat the infection with both antiseptic solutions as well as the appropriate systemic antibiotic. A moist environment should be maintained to allow propagation of reepithelialization, but a balanced approach is necessary to ensure that excess moisture does not result in macerated wound edges. Such management can be done using dressing materials. The last aspect of the TIME mnemonic device refers to the wound edge. The combination of the aforementioned steps helps ensure that epithelium is able to advance and the edges come together to create a healed wound.⁴⁴ 

While acellular products have been shown to be successful in managing DFUs, promoting the closure of nonhealing ulcers, and reducing wound area,^45-48 their use in the management of VLUs is less well studied. In the current study, the authors aim to describe the utility and efficacy of acellular products in the management of VLUs specifically. This review quantifies the effect of acellular products on healing and closing VLUs in the lower extremity, and describes common complications or considerations when using acellular products to heal VLUs.

Search strategy 

An initial literature review was conducted to investigate the utility of ADMs in the management of VLUs. The PubMed, Embase, Cochrane, and Google Scholar online databases were searched on March 2, 2023, using keywords including “acellular dermal matrix”, “acellular dermal matrices”, “venous leg ulcer”, and “vascular leg ulcer” with no restrictions on date, study type, or language. Eighteen articles were obtained from PubMed, 37 from Embase, 3 from the Cochrane database, and 388 from Google Scholar, for an initial total count of 446 articles. After duplicates were removed manually, the remaining 413 articles were screened by title and abstract for relevance. A total of 33 articles progressed to full-text review and were screened for final inclusion based on prespecified inclusion and exclusion criteria. The inclusion criteria were as follows: articles written in or translated into the English language; full-text available; use of ADM on population of patients with VLUs; RCT, prospective cohort, or case series data; and published in the last 5 years (November 1, 2017-March 2, 2023). Exclusion criteria included conference abstracts and data on other non-venous stasis–related ulcers (DFUs, pressure wounds). Following a full-text review, 4 articles remained. Four additional articles were then obtained through collateral methods. Thus, originally, 8 articles were included. 

Upon review of the initial search results, the authors of the current study decided to broaden the search to include any and all acellular matrices rather than only dermal matrices. Thus, another systematic literature search was performed to add to the existing list. On February 20, 2024, a secondary literature search was performed of the Embase, Cochrane, and PubMed databases, using search terms: “acellular” or “decellular” matrix or biomatrix and “vascular” or “venous” leg ulcer, which yielded 580 articles. After duplicates were removed, the remaining articles were screened by title and abstract for relevance. A total of 66 articles progressed to full-text review and were screened for final inclusion based on prespecified inclusion and exclusion criteria. The inclusion criteria were as follows: written in or translated into the English language; full-text available; use of ADM on a population of patients with VLUs; RCT, prospective cohort, or case series data; and published in the last 5 years. Exclusion criteria included conference abstracts, studies on non-ADMs (ie, cell-seeded/cellular product/autologous), and data on other non-venous stasis–related ulcers (DFUs, pressure wounds). Following full-text review, 21 articles remained, which included 3 of the original 8 articles; 1 of the original 8 articles was excluded due to reevaluation of the exclusion/inclusion criteria. In addition to reidentification of the 4 remaining original articles and the acquisition of 2 articles through collateral means, a total of 27 articles were included for analysis (Figure).

Data collection

All included articles were reviewed for bibliographic data, study design, number of participants, and clinical and outcomes data. Primary outcomes collected included wound size, percentage wound area reduction, percentage of complete wound closure, and time to complete wound closure. Secondary outcomes included complication and recurrence rates, and time before treatment (ie, wound chronicity). Data in each of these categories were collected only if they were reported by the authors of the respective study.

Statistical analyses

Descriptive statistics were calculated using mean (SD), median, and ranges as possible using Excel (Microsoft). A meta-analysis of the data could not be performed due to the heterogeneity of included studies and reported data. 

A total of 27 studies were included in this review. Seven studies reported retrospective data, and 19 studies reported prospective data. Studies were published in 1998 through 2023. Four studies were multicenter RCTs (Serena et al,⁴⁶ Cazzell⁴⁷, Vowden et al,⁴⁹ Schmutz et al⁵⁰) (Table).

Two studies were retrospective cohorts (Abeshouse et al,⁵¹ Sabolinski and Gibbons⁵²), and 4 studies were retrospective case series. One study was an indirect single-arm trial utilizing retrospective control data and prospective ADM data (Shannon and Nelson⁵³). A total of 4 studies were level I randomized control trials (Serena et al,⁴⁶ Vowden et al,⁴⁹ Schmutz et al,⁵⁰ Cazzell⁴⁷). Of the total 7 level II studies, four were single-center randomized control trial (Romanelli et al,⁵⁴ Romanelli et al,⁵⁵ Smeets et al,⁵⁶ Cwajda-Białasik et al⁵⁷), and one utilized a retrospectively propensity matched control group (Shannon and Nelson⁵³). A total of 7 studies were level III evidence (Dalac et al,⁵⁸ Harding et al,⁵⁹ Abeshouse et al,⁵¹ Bain et al,⁶⁰ Sabolinski and Gibbons,⁵² Yang Chun et al⁶¹), and a total of 9 articles were level IV case series (Bohn and Glass,⁶² Hodde et al,⁶³ Renner and Simon,⁶⁴ Litwiniuk et al,⁶⁵ Degranges et al,⁶⁶ Greaves et al,⁶⁷ Wozniak et al,⁶⁸ Paredes et al,⁶⁹ Kahn et al⁷⁰). Acellular products used included bovine-derived, acellular dermal replacement (Product A [Integra Dermal Regeneration Template, Integra LifeSciences]); oxidized regenerated cellulose (Product C [Promogran, Solventum Medical]); bovine-derived ADM (Product D [PriMatrix, Integra LifeSciences]); porcine-derived ECM (Product B [OASIS Wound Matrix, Healthpoint, Ltd]); amelogenin hydrogel (Product E [Xelma, Mölnlycke Health Care]); human placental allograft (DHACM [EpiFix, MiMedx]); and decellularized human tissue allograft (Dermacell, Stryker). Other products used included cadaveric tissue-derived matrices, liquid acellular matrices, fish skin grafts, and a variety of synthetic ECMs impregnated with growth factors and antimicrobial agents. Studies included both large and small wound sizes ranging from 0.5 cm² to 100 cm². Most studies examined VLUs that ranged in size from 11 cm² to 50 cm². Product application occurred once to twice weekly for 4 weeks to 36 months. Most studies focused on skin substitute performance in the earlier phases of wound healing, with 80% of studies evaluating wounds between 4 weeks and 16 weeks from the time of product application. Wound assessment focused primarily on the rate and degree of wound SA reduction. 

Wound SA reduction

By 4 weeks after product application, average SA reduction greater than or equal to 40% was achieved in the majority of wounds. One prospective RCT studied 84 VLUs (53 treated with allograft and 31 treated with SOC) with an average SA of 6.0 cm² and found a 48.1% reduction in wound SA in ulcers treated with dHACM allograft compared with only a 19.0% reduction in ulcers treated with SOC.⁴⁶ Litwiniuk et al⁶⁵ examined the use of an amniotic allograft impregnated with growth factor in 25 VLUs and reported accelerated reepithelialization after 28 days of weekly treatment. 

Multiple studies reported accelerated VLU area reduction with the use of porcine-derived matrices.^54,55,63 One study also reported fewer dressing changes with the use of porcine-based products compared with the control group.⁴⁹ 

Ovine-based products have also shown promise in the management of VLUs. Bohn and Gass⁶² examined the use of an ovine collagen ECM dressing in 23 VLUs with an average SA of 3.7 cm² and reported that the average surface area reduction of all 23 wounds was 97.9% at 12 weeks after weekly dressing changes.

One novel approach to the management of hard-to-heal VLUs is the use of fish skin grafts, which have achieved results comparable to those of other acellular matrices in terms of wound size reduction. In a study of 18 VLUs with an average initial SA of 8.2 cm², the use of acellular fish-skin matrix resulted in a 40% decrease in wound SA and a 48% decrease in wound depth after 5 weekly applications (P < .05 for both).⁶¹ The authors of that study suggested that the omega-3 anti-inflammatory properties of the fat component of the graft likely contribute to the ability of such grafts to successfully promote ulcer healing. 

Three studies examined larger VLUs with an average wound SA greater than or equal to 50 cm².^50,65,71 Litwiniuk et al⁶⁵ used a radiation-sterilized amniotic dressing impregnated with hyaluronan and growth factors to treat 25 treatment-refractory VLUs as large as 100 cm² (range, 10 cm²-100 cm²) over a period of 28 days. Wound conditions were assessed at each weekly dressing change. Ulcer progression was graded using the Bates-Jensen wound assessment tool, which is used to characterize wounds based on 13 parameters, including size, depth, edges, undermining, necrotic tissue type, discoloration, granulation tissue, and epithelialization; lower scores indicate healthier wounds.⁷² In the Litwiniuk et al⁶⁵ study, treatment with the amniotic dressing resulted in a “good” or “satisfactory” wound response in 23 of 25 VLUs, indicated by a Bates-Jensen wound assessment tool score reduction of 1.7 to 3.5 points per week over the total treatment period. The authors of that study specifically cited granular tissue simulation and faster reepithelialization as the primary variables that were favorably affected by the dressing. 

Similarly, Wollina et al⁷¹ reported improved VLU healing as a direct result of improved granulation and reepithelialization in wounds treated with a bovine-derived collagen product (Product C) characterized by an oxidized regenerated cellulose matrix. The study randomized 40 VLUs to receive SOC (compression therapy and regular debridement) or Product C plus SOC. The average initial wound SA was 59 cm² in each study group. Wounds treated with Product C had a mean wound SA reduction of 493 mm² by one week and 903 mm² by 2 weeks, compared to only 404 mm² SA reduction after 1 week in the control group (P < .05).⁷¹ Additionally, wounds were scored based on granulation, color, and consistency, with higher scores indicating a healthier wound bed. The overall wound score in the wounds treated with Product C improved from a mean (SD) of 2.28 (1.24) before treatment to 3.72 (1.57) after 1 week (P < .00023) and 4.92 (1.68) after 2 weeks (P < .000027). However, comparable wound score results were reported in the SOC-treated wounds, which showed a mean improvement in wound score from 1.44 (1.33) before treatment to 3.22 (1.30) after 1 week (P < .0077).⁷¹ 

A different study compared Product C with a lipido-colloid-MMP antagonist matrix (NOSF UrgoStart) in the treatment of 117 VLUs with a mean SA of 11.2 ± 7.4 cm² at baseline.⁵⁰ By 6 months after initial product application, wound area reduction was superior in NOSF-treated wounds, with leg ulcer regression greater than or equal to 40% observed in 55% of NOSF-treated wounds compared with only 26% of wounds in the Product C group (P = .016). 

Product A, another well-known bovine-derived skin substitute, has been reported to augment nonhealing DFUs.³⁵ However, few studies have examined the efficacy of that product in nonhealing VLUs. One such study treated a total of 10 VLUs with an average SA of 96.8 cm² with Product A plus negative pressure wound therapy followed by STSG for 10 days. Results showed high rates of STSG take in the Product A-treated wounds, with a reported 90% take at 14 days of treatment.⁷⁰ Similarly, Abeshouse et al⁵¹ reported a 92% STSG success rate after an average of 8.5 weeks of treatment with Product D, further demonstrating the ability of skin substitutes to act as a bridge to successful skin grafting in the setting of chronic VLUs.

Wound closure and time to healing

Thirteen studies used total wounds closed and/or time to healing as primary end points. Cazzell⁴⁷ reported a higher wound closure rate with a single application of D-ADM (44.4% [4 of 9]) than with conventional care (33.3% [3 of 9]). However, when combined with patients who received 2 applications, the wound closure rate was 29.4% (5 of 17), which was comparable to that of the control group (33.3%). Fifty percent (9/18) of patients in the experimental group required only a single application of D-ADM, while another 50.0% (9/18) required 2 applications. Additionally, at 24-week follow-up, 44.4% (8/18) of wounds treated with D-ADM remained closed, whereas only 33.3% (3/9) of the wounds in the control group remained closed. Sabolinski and Gibbons⁵² reported significantly higher rates of wound closure in patients treated with bilayered living cellular construct than in those treated with acellular fetal bovine collagen dressing (31% vs 25% at 12 weeks). They also demonstrated significantly shorter time to wound closure with use of the bilayered living cellular construct compared with acellular fetal bovine collagen dressing (19 weeks vs 30 weeks; P = .01). 

Paredes et al⁶⁹ reported a wound closure rate of 38% at 16 weeks and median time to wound closure of 67 days using Product D. Romanelli et al⁵⁴ compared a novel porcine Product B against moist wound dressings (ie, SOC). The Product B group exhibited significantly faster times to complete wound healing, with an average of 5.4 weeks compared with 8.3 weeks in the SOC group (P = .02). Complete wound closure of 80% and 65% was achieved in the Product B and SOC groups, respectively, at 8 weeks.⁵⁴ Harding et al⁵⁹ reported complete epithelialization at 12 weeks in 35.6% of wounds treated with a synthetic ECM protein with vitronectin and IGF-1. A different study used ovine collagen ECM dressing in the management of small VLUs (mean, 3.7 cm²) and reported 100% wound healing during the study period (n = 23), with an average of 7.3 weeks to closure.⁶² Renner and Simon⁶⁴ used an amelogenin hydrogel (Product E) in the management of VLUs, resulting in closure (ie, >90% epithelialization) in 42% of granulated ulcers and 56% of sclerotic ulcers. In a different study, use of a bioengineered structural analog of heparan sulfate glycosaminoglycan led to closure at 12-week follow-up of 50% of VLUs (7 of 14) with an average size at baseline of 14.15 cm².⁶⁶ Campitiello et al⁷³ reported time to wound closure of 15 days in the group treated with ADMs. In a single-arm study, Bain et al⁶⁰ used a type I collagen matrix with polyhexamethylene biguanide antimicrobial in the management of 67 VLUs and reported an average time to wound closure of 22 weeks for the bilayered living cellular construct and fetal bovine collagen dressing groups, respectively. Shannon and Nelson⁵³ also reported significantly decreased times to wound closure of 84 and 92 days, respectively, compared with 73 days for the control group. Only 1 study, by Smeets et al,⁵⁶ did not find any significant differences in wound closure between a collagen matrix and SOC.

MMPs and cellular analysis

The management of chronic VLUs is associated with significant challenges, including persistent inflammation and an imbalance between proteolytic activity and tissue repair mechanisms. MMPs play an important role in this imbalance, because increased MMP activity results in excessive ECM degradation. 

In a study by Hodde et al,⁶³ 12 participants were enrolled to assess the effects of SIS wound matrix on chronic VLUs. Notably, 7 participants experienced wound healing (“responsive wounds”) during the 12-week follow-up period. The responsive wounds demonstrated a significant reduction in levels of several key MMPs compared with baseline levels, which contrasted sharply with levels in nonresponsive wounds. MMP-1 levels decreased to 42.1% of baseline in responsive wounds and increased to 415.1% of baseline in nonresponsive wounds (P < .05), and similar trends were observed with levels of MMP-2 (66.4% vs 254.7%, respectively; P = .05), MMP-3 (66.3% vs 388.1%, respectively; P < .05), and MMP-9 (54.8% vs 666.1%, respectively; P < .01).⁶³

Litwiniuk et al⁶⁵ investigated the effects of radiation-sterilized amnion dressings on chronic VLUs, and collected wound exudate samples to assess the activities of MMP-2 and MMP-9. Samples were collected on day 0 (prior to amnion application) and on day 28. In this study as well, MMP levels decreased during wound healing. Over the 28-day follow-up period, median levels of MMP-2 decreased from 251 ng/mL to 178 ng/mL, and median levels of MMP-9 decreased from 293 ng/mL to 219 ng/mL.⁶⁵ 

These results highlight the role of MMPs in the pathology of chronic VLUs, as well as the therapeutic potential for acellular matrices to decrease the activity of MMPs. 

Bacteriology

Several studies reported on the antimicrobial properties and effects on wound bacteria of the evaluated skin substitutes and matrices. Dalac et al⁵⁸ evaluated a dressing with poly absorbent fibers and a silver lipido-colloid matrix (TLC-Ag - UrgoClean Ag; Laboratoires URGO, Chenôve, France) and found it provided antimicrobial benefits, with only 1 patient reporting potential pain related to the silver content. Markoishvili et al⁷⁴ studied a biodegradable polymer matrix impregnated with bacteriophages, the antibiotic ciprofloxacin, and other antimicrobial agents (PhagoBioDerm - Phage International, Georgia). They reported complete healing in 70% of the 96 patients treated, with no systemic effects observed related to the antimicrobial components in the matrix. Smeets et al⁵⁶ compared an oxidized regenerated cellulose/collagen matrix with SOC and reported that the former significantly decreased elastase, plasmin, and gelatinase activity in the wound exudates of chronic VLUs. These results suggest that the matrix reduced protease activity and bacterial burden compared with control therapy. Similarly, Yonezawa et al⁷⁵ evaluated a cultured dermal substitute containing antimicrobial components like growth factors and found that only 1 of 13 patients experienced a local wound infection during treatment. Similarly, Yonezawa et al evaluated a cultured dermal substitute that releases various growth factors such as VEGF, bFGF, and PDGF, and found that only 1 of 13 patients had to discontinue treatment due to infection. In contrast, Bohn and Gass⁶² did not report any adverse effects or events associated with use of a bovine collagen ECM dressing that lacked antimicrobial agents in the management of VLUs. 

Overall, the results of these studies indicate that incorporating antimicrobial agents into skin substitute/matrix products can provide benefits in reducing wound bioburden and supporting healing. Overall, the results of these studies suggest that incorporating antimicrobial agents into skin substitute/matrix products may provide benefits in reducing wound bioburden and supporting healing, though products without antimicrobial agents can also be effective in managing chronic wounds. Further research is needed to fully determine the impact of antimicrobial components in these products on wound healing outcomes.

Pain

Only 33.33% of included studies (n = 9) reported pain as an outcome measurement with use of the acellular products on VLUs. The following skin substitute types were included in these studies: freeze-dried sponge prepared from bovine collagen and oxidized regenerated cellulose (Product C matrix), synthetic ECM protein with portions of vitronectin and IGF-1, natural ECM replacement that contains all of the major dermal ECM components (Product B), only a single component of the ECM (Hyaloskin, Product F), acellular fish-matrix ECM with fats, nano-oligosaccharide factor incorporated within a lipido-colloid matrix aimed at promoting wound closure through MMP inhibition (NOSF), Technology Lipido-Colloid Silver healing matrix, cutaneous wound ECM protein equivalent (Product E), factor XIII (Fibrogammin HS, plasma-deprived factor XIII concentrate; CSL Behring), and dHACM allograft. Two of the 9 studies reported on Product C, while 4 of the 9 studies mentioned ECM protein ADM types. 

The 2 studies that investigated the Product C matrix reported opposite findings for VLU pain scores. The first study used the VAS to measure pain associated with wounds and investigated the Product C matrix compared with “good” ulcer care with hydropolymer (polyurethane) or hydrocolloid dressings.⁷¹ This study reported a statistically significant reduction in pain scores for the Product C matrix group from baseline to the end of week 2 from 8.72 to 3.84 (P < .05). The study authors concluded that use of the Product C matrix reduced the pain score by 33.9% in 1 week and 56.0% in 2 weeks, resulting in more effective pain improvement compared with the control treatment.⁷¹ The second study compared the NOSF matrix with the Product C matrix and reported that pain was more frequent in the Product C cohort than in the NOSF cohort.⁵⁰ The authors of that study also indicated that the severe pain in patients who received Product C was the reason for discontinuation of that treatment. 

Most studies that analyzed synthetic ECM protein demonstrated improved pain scores after ECM acellular matrix application. Some studies used VAS scoring, while others used their own pain scales. One study analyzed synthetic ECM protein with portions of vitronectin and IGF-1 and found that 87% of patients had no pain at 12 weeks (based on VAS score); all patients reported meaningful pain reduction.⁵⁹ Another study that used the VAS to measure pain reported significantly greater comfort and less pain in ulcers treated with Product B compared with Product F.⁵⁵ A different study used a pain scale from 0 to 10 (0, negligible pain; 10, unbearable pain).⁴⁹ The study authors reported that Product E had higher baseline pain scores (mean pain scores of 4 and 3, respectively) than in the control group (propylene glycol alginate 7%) and that in both groups the mean pain score decreased to 1 at the final visit. However, the authors concluded that patients treated with Product E had less pain compared with the control group. The last study used acellular fish-matrix ECM with fatty acids and reported no significant difference in pain scores.⁶¹ Two studies reported significant pain reduction for both acellular product types. One study investigated plasma-deprived factor XIII concentrate and indicated that all patients experienced a reduction in pain intensity during bandaging.⁶⁸ The other study indicated that 79.5% of patients treated with dHACM had significant pain reduction, compared with 52.4% in the control group.⁴⁶ One study investigated TLC-Ag use in 36 VLUs with a mean (SD) size of 13.5 (14.6) cm² and reported 1 patient who withdrew from the study due to pain but did not report other pain outcomes.⁵⁸ All of these results demonstrate that ADMs may have a positive effect on pain reduction in VLUs; however, further studies should streamline data for each product in order to have a deeper understanding on impact of pain reduction in VLUs.

Complications

The majority of the included studies reported on whether patients experienced complications with the use of an acellular product in the management of VLUs. In 68.4% of the studies that reported on complications (13 of 19), none of the patients experienced any adverse events. In the study by Schmutz et al,⁵⁰ 16 local adverse events in 14 of the 57 patients in the NOSF group were reported (24.5%), and 27 local adverse events in 23 of the 60 patients in the Product C (ie, control) group were reported (38.3%). Perilesional skin irritation occurred in 7 patients in the NOSF group (12.3%) and in 8 patients in the control group (13.3%). Pain between dressing changes was reported in 4 patients in the NOSF group (8.8%) and in 12 patients in the control group (20.0%). Overgranulation occurred in 4 patients in the NOSF group (7.0%) and in 1 patient in the control group (1.7%). Infection was reported in 1 patient in the NOSF group (7.0%) and in 6 patients in the control group (10.0%). Six patients in the treatment group (10.5%) and 14 patients in the control group (23.3%) discontinued treatment with the tested matrices due to local adverse events.⁵⁰ In the study by Dalac et al,⁵⁸ 1 of the 36 patients experienced pain that was presumed to be related to treatment with Technology Lipido-Colloid Silver healing matrix; this pain led to their withdrawal from the study (2.78%). In the study by Greaves et al,⁶⁷ 3 of 20 patients treated with the decellularized dermal matrix product experienced infection (15%); oral antibiotics were sufficient to treat these infections. Vowden et al⁴⁹ reported 3 serious adverse events in the group that underwent treatment with amelogenin; however, none of these events could be directly attributed to the treatment and instead likely were related to the complex patient population. In the control group, 3 adverse events were reported, 1 of which was attributable to the treatment. The authors did not provide detail about the precise nature of the adverse event. Serena et al⁴⁶ reported 4 adverse events in the group of patients who underwent treatment with a dHACM allograft in addition to multilayer compression therapy that were possibly related to the treatment. These adverse events included 2 cases of cellulitis on the affected extremity, 1 wound infection, and 1 wound with increased drainage and abscess. In the group of patients who underwent treatment with multilayer compression therapy alone, 3 adverse events were possibly related to the treatment; these events included 2 cases of wound infection and 1 case of maceration around the wound with increased drainage.⁴⁶ Collectively, these results indicate that management of VLUs with ADMs is safe; however, patients should be monitored for the development of local adverse events, because these have been reported.

The strengths of the current review include a broad range of acellular product types, a wide range of wound sizes, and a focus on lower limb ulcers beyond DFUs. The majority of included studies demonstrated the ability of acellular products to accelerate wound area reduction, facilitate successful wound closure, reduce wound area pain, and reduce the risk of wound infection with the use of antimicrobial-impregnated products. Furthermore, certain studies demonstrated the ability of acellular products to decrease wound inflammation through the reduction of MMP expression. It is important to note that while the application of acellular products can improve elasticity and range of motion in upper extremity wounds, their use is not without complications.⁷⁶ Skin contracture has been reported as a complication of ADM use in tumor resection surgery and radial forearm flap donor site closure.^77,78 Other potential complications include incomplete innervation, hypopigmentation, lack of vascularization, and absence of hair follicles, sweat, and sebaceous glands.¹⁹ However, several studies in the current review demonstrated the utility of acellular products as an adjunct to VLU treatment with few complications. Furthermore, this review highlights the potential role of such products to function as a bridge to successful skin grafting in chronic VLUs. These findings are consistent with previous reports of success rates as high as 97% with acellular product application in combination with skin grafting in lower limb wounds.¹⁹ One suggested benefit of acellular matrices as a precursor to skin grafting is that acellular matrices “are able to mimic the composition of the native extracellular matrix…because the lack of a functional extracellular matrix is the main cause affecting the impaired wound healing process.”⁷⁹

Acellular product use on a VLU depends on several factors, such as the location and size of the wound, as well as the overall health condition of the patient. For example, the current review found that lipido-colloid-based matrices (NOSF) may be particularly effective in larger-sized ulcers (>10 cm²).⁵⁰ However, regardless of ulcer size or the type of acellular product used, SOC with biofilm management for wound bed preparation before any product application remains a critical step in the successful management of VLUs. An effective wound bed preparation model includes debridement and wound cleansing, inflammation and infection control, moisture management, support for granulation and epithelialization, and support to help achieve treatment goals and objectives.  

Alternative approaches to the use of skin substitutes in the management of VLUs include the use of placental allograft, which the current review highlights has shown remarkable success in the achievement of complete VLU closure compared with SOC. In vitro studies have also demonstrated that placental ADMs contain a high level of pro-angiogenic factors such as angiopoietin, angiogenin, and platelet-derived growth factor.^80,81 Thus, “[placental ADMs] usage promotes revascularization, preventing necrosis, granulomatous inflammation, and formation of a fibrous capsule.”⁴⁹ Additionally, antibacterial peptides such as defensins and cathelicidin are expressed in these placental-derived ADMs. This is especially important for VLUs, which often manifest as a biofilm environment. 

Of equal importance is the emergence of fish skin grafts as a new area of focus in the management of chronic wounds. One RCT of 97 adults with VLUs found an overall greater number of completely healed ulcers in the topical fish collagen treatment group vs the control group (week 12: 29.2% vs 22.4%; week 24: 52.1% vs 36.7%), as well as faster healing time in both big and small ulcers in the treatment group.⁵⁷ Furthermore, thermographic analysis showed statistically significant reduction in periwound inflammation among patients in the fish collagen group (P < .05). A study of 170 acute biopsy wounds found that wounds treated with fish skin healed significantly faster (hazard ratio 2.37; 95% CI, 1.75–3.22; P = .0014) compared with wounds treated with dHACM.⁸³ The findings of the current review support the utility of acellular fish skin grafts in the management of VLUs.  Some authors have suggested that fish skin grafts are gently processed, hence, the natural structural and molecular composition of the extracellular matrix are preserved.  The former is thought to provide a locus for cellular recognition which may aid wound healing.⁸³ 

Cost efficiency has been reported in a variety of acellular product applications. One study compared ADMs with traditional tissue expander/implant-based breast reconstruction (without ADM) and found that single-stage implant with ADM was most cost-effective, with a cost of $5432.02 compared with $10 934.18 with tissue expander/implant alone.⁸⁴ The cost analysis also incorporated the probability of complications as a result of each procedure. Other studies have suggested that immediate single-stage implant reconstruction with ADMs are cost-effective and have low complication rates.⁸⁵ Treatment costs for VLUs, which are directly related to time to achieve complete closure, average approximately $4000 per month and $16 000 per treatment episode.⁷ Massand et al⁸⁶ identified RCTs that compared AWCMs with standard compression therapy in the healing of VLUs and found significant variation in terms of cost efficacy reporting and results. However, some studies those authors identified indicated a suggested cost benefit with the use of ADMs in VLUs. Tennvall et al⁸⁷ noted that health insurance plans generally restrict coverage and reimbursement of AWCMs to patients for whom compression therapy has been unsuccessful; however, the recruitment of AWCMs earlier in the VLU treatment process may reduce long-term costs by potentially decreasing wound chronicity, thus potentially minimizing the number of required hospital visits, the prolonged cost of wound care supplies, and the need for more costly invasive wound management surgical procedures. In patients with risk factors for arterial disease, it is important to determine whether the wounds are arterial or venous in nature (or mixed) and perform an arterial workup prior to placing an acellular product.⁸⁸ 

There is no doubt of the importance of a staged approach to VLU treatment. Despite the paucity of studies evaluating the effect of acellular products on VLU outcomes, their utility as a potential adjunct to VLU management has become evident. In terms of when to consider the use of an ADM on a VLU, 1 study reported wound size greater than 5 cm² and duration of more than 3 months as strong indicators of hard-to-heal VLUs,⁸⁹ suggesting that these parameters could potentially help clinicians and care providers determine when to use an acellular product. More research is needed to investigate the overall suitability of acellular products in the management of VLUs and to determine the most appropriate approach to their use in the affected patient population.^83,90 

Although this narrative review aims to provide a comprehensive overview of the existing literature on the use of acellular products in VLUs, it has limitations. The heterogeneity of included studies is a limitation. The studies encompass a range of methodologies, as discussed in the “Results” section. The methodologic diversity among these studies introduced research heterogeneity that made direct comparison and synthesis difficult. Additionally, the individual studies had low sample sizes, which made generalizability of the results difficult. Finally, due to the study heterogeneity and overall small sample sizes, a quantitative meta-analysis was not possible. Instead, descriptive statistics were used to summarize the findings. Although this approach offers a valuable understanding of the existing literature, it does not offer a quantifiable summary of statistical significance. These limitations are likely the result of an overall paucity of literature on the use of acellular matrices in the management of VLUs.

The wide range of wound sizes studied as well as the wide range in wound reductions underscores the complexity of using acellular matrices to manage VLUs. Despite promising wound reductions seen in some cases, complications such as infection and local skin irritation highlight the need for more research on the efficacy of ADMs. Finally, the emerging alternative approaches to the use of skin substitution (eg, fish skin grafts) adds further complexity concerning how and when to leverage acellular products. Ongoing research is necessary to identify the optimal role of ADMs in the management of VLU. 

Authors: Tokoya Williams, MD; Stuti P. Garg, BA; Keenan Fine, MS; Bradley Melnick, BS; Kelly Ho, BS; Madeline O’Connor, BA; Sammer Marzouk, MA; Antoinette Nguyen, BA; Abbey Landini, BA; Prottusha Sarkar, BA; Kirtana Sandepudi, MS; Fatoumata Sylla, BA; Brigid Coles, BA; and Robert D. Galiano, MD

Affiliation: Division of Plastic and Reconstructive Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL

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

Correspondence: Robert D. Galiano, MD; Northwestern Medicine Division of Plastic and Reconstructive Surgery, 259 E Erie Street, Lavin 20-2060, Chicago, IL 60611; robert.galiano@nm.org 

Manuscript Accepted: April 25, 2024