A randomized controlled trial of cultured keratinocyte allografts for chronic venous ulcers

Dressings and topical agents for treating venous leg ulcers

BACKGROUND

Venous leg ulcers are open skin wounds on the lower leg which can be slow to heal, and are both painful and costly. The point prevalence of open venous leg ulcers in the UK is about 3 cases per 10,000 people, and many people experience recurrent episodes of prolonged ulceration. First-line treatment for venous leg ulcers is compression therapy, but a wide range of dressings and topical treatments are also used. This diversity of treatments makes evidence-based decision-making challenging, and a clear and current overview of all the evidence is required. This review is a network meta-analysis (NMA) which assesses the probability of complete ulcer healing associated with alternative dressings and topical agents.

OBJECTIVES

To assess the effects of (1) dressings and (2) topical agents for healing venous leg ulcers in any care setting and to rank treatments in order of effectiveness, with assessment of uncertainty and evidence quality.

SEARCH METHODS

In March 2017 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also scanned reference lists of relevant included studies as well as reviews, meta-analyses, guidelines and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting. We updated this search in March 2018; as a result several studies are awaiting classification.

SELECTION CRITERIA

We included published or unpublished randomised controlled trials (RCTs) that enrolled adults with venous leg ulcers and compared the effects of at least one of the following interventions with any other intervention in the treatment of venous leg ulcers: any dressing, or any topical agent applied directly to an open venous leg ulcer and left in situ. We excluded from this review dressings attached to external devices such as negative pressure wound therapies, skin grafts, growth factors and other biological agents, larval therapy and treatments such as laser, heat or ultrasound. Studies were required to report complete wound healing to be eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, 'Risk of bias' assessment and data extraction. We conducted this NMA using frequentist meta-regression methods for the efficacy outcome; the probability of complete healing. We assumed that treatment effects were similar within dressings classes (e.g. hydrocolloid, foam). We present estimates of effect with their 95% confidence intervals (CIs) for individual treatments focusing on comparisons with widely used dressing classes, and we report ranking probabilities for each intervention (probability of being the best, second best, etc treatment). We assessed the certainty (quality) of the body of evidence using GRADE for each network comparison and for the network as whole.

MAIN RESULTS

We included 78 RCTs (7014 participants) in this review. Of these, 59 studies (5156 participants, 25 different interventions) were included in the NMA; resulting in 40 direct contrasts which informed 300 mixed-treatment contrasts.The evidence for the network as a whole was of low certainty. This judgement was based on the sparsity of the network leading to imprecision and the general high risk of bias in the included studies. Sensitivity analyses also demonstrated instability in key aspects of the network and results are reported for the extended sensitivity analysis. Evidence for individual contrasts was mainly judged to be low or very low certainty.The uncertainty was perpetuated when the results were considered by ranking the treatments in terms of the probability that they were the most effective for ulcer healing, with many treatments having similar, low, probabilities of being the best treatment. The two most highly-ranked treatments both had more than 50% probability of being the best (sucralfate and silver dressings). However, the data for sucralfate was from one small study, which means that this finding should be interpreted with caution. When exploring the data for silver and sucralfate compared with widely-used dressing classes, there was some evidence that silver dressings may increase the probability of venous leg ulcer healing, compared with nonadherent dressings: RR 2.43, 95% CI 1.58 to 3.74 (moderate-certainty evidence in the context of a low-certainty network). For all other combinations of these five interventions it was unclear whether the intervention increased the probability of healing; in each case this was low- or very low-certainty evidence as a consequence of one or more of imprecision, risk of bias and inconsistency.

AUTHORS' CONCLUSIONS

More research is needed to determine whether particular dressings or topical agents improve the probability of healing of venous leg ulcers. However, the NMA is uninformative regarding which interventions might best be included in a large trial, largely because of the low certainty of the whole network and of individual comparisons.The results of this NMA focus exclusively on complete healing; whilst this is of key importance to people living with venous leg ulcers, clinicians may wish to take into account other patient-important outcomes and factors such as patient preference and cost.

Synthetic polymeric biomaterials for wound healing: a review

Wounds are of a variety of types and each category has its own distinctive healing requirements. This realization has spurred the development of a myriad of wound dressings, each with specific characteristics. It is unrealistic to expect a singular dressing to embrace all characteristics that would fulfill generic needs for wound healing. However, each dressing may approach the ideal requirements by deviating from the 'one size fits all approach', if it conforms strictly to the specifications of the wound and the patient. Indeed, a functional wound dressing should achieve healing of the wound with minimal time and cost expenditures. This article offers an insight into several different types of polymeric materials clinically used in wound dressings and the events taking place at cellular level, which aid the process of healing, while the biomaterial dressing interacts with the body tissue. Hence, the significance of using synthetic polymer films, foam dressings, hydrocolloids, alginate dressings, and hydrogels has been reviewed, and the properties of these materials that conform to wound-healing requirements have been explored. A special section on bioactive dressings and bioengineered skin substitutes that play an active part in healing process has been re-examined in this work.

Skin grafting for venous leg ulcers

BACKGROUND

Venous leg ulceration is a recurrent, chronic, disabling condition. It affects up to one in 100 people at some time in their lives. Standard treatments are simple dressings and compression bandages or stockings. Sometimes, despite treatment, ulcers remain open for months or years. Sometimes skin grafts are used to stimulate healing. These may be taken, or grown into a dressing, from the patient's own uninjured skin (autografts), or applied as a sheet of bioengineered skin grown from donor cells (allograft). Preserved skin from other animals, such as pigs, has also been used (xenografts).

OBJECTIVES

To assess the effect of skin grafts for treating venous leg ulcers.

SEARCH METHODS

For this update we modified the search strategies and conducted searches of The Cochrane Wounds Group Specialised Register (searched 27 July 2012); The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 7); Ovid MEDLINE (2008 to July Week 3 2012); Ovid MEDLINE (In-Process & Other Non-Indexed Citations, July 26, 2012); Ovid EMBASE (2008 to 2012 Week 29); and EBSCO CINAHL (2008 to 26 July 2012). We did not apply date or language restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of skin grafts in the treatment of venous leg ulcers.

DATA COLLECTION AND ANALYSIS

Two review authors independently undertook data extraction and assessment of study quality.

MAIN RESULTS

For this update of the review, we identified one new trial, bringing the total to 17 trials (1034 participants) - all of which were generally at moderate or high risk of bias. In 12 trials participants also received compression bandaging.Eleven trials compared a graft with standard care in which no graft was used. Two of these trials (102 participants) compared a dressing with an autograft; three trials (80 participants) compared frozen allografts with dressings, and two trials (45 participants) compared fresh allografts with dressings. Two trials (345 participants) compared tissue-engineered skin (bilayer artificial skin) with a dressing. In two trials (97 participants) a single-layer dermal replacement was compared with standard care.Six trials compared alternative skin grafting techniques. The first trial (92 participants) compared autografts with frozen allograft, a second (51 participants) compared a pinch graft (autograft) with porcine dermis (xenograft), the third (110 participants) compared growth-arrested human keratinocytes and fibroblasts with placebo, the fourth (10 participants) compared an autograft delivered on porcine pads with an autograft delivered on porcine gelatin microbeads, the fifth trial (92 participants) compared a meshed graft with a cultured keratinocyte autograft, and the sixth trial (50 participants) compared a frozen keratinocyte allograft with a lyophilised (freeze-dried) keratinocyte allografts.Significantly more ulcers healed when treated with bilayer artificial skin than with dressings. There was insufficient evidence from the other trials to determine whether other types of skin grafting increased the healing of venous ulcers.

AUTHORS' CONCLUSIONS

Bilayer artificial skin, used in conjunction with compression bandaging, increases venous ulcer healing compared with a simple dressing plus compression. Further research is needed to assess whether other forms of skin grafts increase ulcer healing.

Skin grafting for venous leg ulcers

BACKGROUND

Venous leg ulceration is a recurrent, chronic, disabling condition. It affects up to one in 100 adults at some time. Standard treatments are simple dressings and compression bandages or stockings. Sometimes, despite treatment, ulcers remain open for months or years. Sometimes skin grafts are used to stimulate healing. These may be taken, or grown into a dressing, from the patient's own uninjured skin (autografts), or applied as a sheet of bioengineered skin grown from donor cells (allograft). Preserved skin from other animals, such as pigs, has also been used (xenografts).

OBJECTIVES

To assess the effect of skin grafts for treating venous leg ulcers.

SEARCH STRATEGY

We searched the Cochrane Wounds Group Specialised Register (February 2006) and the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2006).

SELECTION CRITERIA

Randomised controlled trials (RCTs) of skin grafts in the treatment of venous leg ulcers.

DATA COLLECTION AND ANALYSIS

Two reviewers independently undertook data extraction and assessment of study quality.

MAIN RESULTS

We identified 15 trials - generally of poor methodological quality - involving 768 participants. In 11 trials participants also received compression bandaging. One trial (31 participants) compared a dressing with an autograft. Three trials (74 participants) compared frozen allografts with dressings, and three trials (47 participants) compared fresh allografts with dressings. Two trials (345 participants) compared tissue-engineered skin (bilayer artificial skin) with a dressing. In two trials (71 participants) a single-layer dermal replacement was compared with standard care. Four trials compared skin grafting techniques: one trial (92 participants) compared autografts with frozen allograft, a second (51 participants) compared a pinch graft (autograft) with a porcine dermis (xenograft), the third (seven participants, 12 ulcers) compared tissue-engineered skin with a split-thickness graft, the fourth (10 participants) compared a fresh allograft with a frozen allograft. The trials comparing bilayer artificial skin with a dressing reported a significantly higher proportion of ulcers healing with artificial skin. There was not enough evidence from the other trials to determine whether other types of skin grafting increased the healing of venous ulcers.

AUTHORS' CONCLUSIONS

Bilayer artificial skin, used in conjunction with compression bandaging, increases the chance of healing a venous ulcer compared with compression and a simple dressing. Further research is needed to assess whether other forms of skin grafts increase ulcer healing.

Skin grafting for venous leg ulcers

BACKGROUND

Venous leg ulceration is a common and disabling condition which often recurs. It affects up to one in 100 adults at some time. The usual treatments are simple dressings and compression bandages or stockings. Unfortunately, in some cases this treatment is unsuccessful, with ulcers remaining open for months or years. Sometimes skin grafts are used to stimulate healing. These skin grafts may be taken from the patient's own uninjured skin, may be grown from the patient's skin cells into a dressing (autografts), or applied as a sheet of bioengineered skin grown from donor cells (allograft). Preserved skin from other animals, such as pigs, has also been used; these grafts are known as xerografts.

OBJECTIVES

To assess the effect of skin grafts for treating venous leg ulcers.

SEARCH STRATEGY

We searched the Cochrane Wounds Group Specialised Register (June 2004) and the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2004).

SELECTION CRITERIA

Randomised controlled trials (RCTs) of skin grafts in the treatment of venous leg ulcers.

DATA COLLECTION AND ANALYSIS

Two reviewers independently undertook data extraction and assessment of study quality.

MAIN RESULTS

Nine trials of skin grafts for venous leg ulcers were identified, involving 579 participants. The trials were generally of poor methodological quality. In eight trials participants also received compression bandaging. Two trials (98 participants) evaluated split thickness autografts (one against a dressing and one against a xerograft), four trials (119 participants) evaluated cultured keratinocyte grafts (3 allografts and 1 autograft) , two compared tissue engineered skin (bilayer artificial skin) with a dressing (345 participants), and one compared it with a split thickness skin graft (7 participants, 13 ulcers). The trials comparing bilayer artificial skin with a dressing reported a significantly higher proportion of ulcers healing with artificial skin. There was not enough evidence from the other trials to determine whether other types of skin grafting increased the healing of venous ulcers.

AUTHORS' CONCLUSIONS

There is evidence that a bilayer artificial skin, used in conjunction with compression bandaging, increases the chance of healing a venous ulcer compared with compression and a simple dressing. Further research is needed to assess whether other forms of skin grafts increase ulcer healing.

Skin Grafting of Venous Ulcers: A Review of its Current Role

As a therapeutic option, grafting of venous ulcers has not been very successfully received despite the different types of grafting methods. Currently, there are only a few controlled randomized trials offering clear guidance to clinicians. The development of artificially bioengineered skin constructs has led to a renewed interest in wound bed preparation, and preliminary successes suggest that the role of skin grafting could be studied in the current context.

Tissue-engineered skin. Current status in wound healing

Tissue-engineered skin is a significant advance in the field of wound healing and was developed due to limitations associated with the use of autografts. These limitations include the creation of a donor site which is at risk of developing pain, scarring, infection and/or slow healing. A number of products are commercially available and many others are in development. Cultured epidermal autografts can provide permanent coverage of large area from a skin biopsy. However, 3 weeks are needed for graft cultivation. Cultured epidermal allografts are available immediately and no biopsy is necessary. They can be cryopreserved and banked, but are not currently commercially available. A nonliving allogeneic acellular dermal matrix with intact basement membrane complex (Alloderm) is immunologically inert. It prepares the wound bed for grafting allowing improved cultured allograft 'take' and provides an intact basement membrane. A nonliving extracellular matrix of collagen and chondroitin-6-sulfate with silicone backing (Integra) serves to generate neodermis. A collagen and glycosaminoglycan dermal matrix inoculated with autologous fibroblasts and keratinocytes has been investigated but is not commercially available. It requires 3 to 4 weeks for cultivation. Dermagraft consists of living allogeneic dermal fibroblasts grown on degradable scaffold. It has good resistance to tearing. An extracellular matrix generated by allogeneic human dermal fibroblasts (TransCyte) serves as a matrix for neodermis generation. Apligraf is a living allogeneic bilayered construct containing keratinocytes, fibroblasts and bovine type I collagen. It can be used on an outpatient basis and avoids the need for a donor site wound. Another living skin equivalent, composite cultured skin (OrCel), consists of allogeneic fibroblasts and keratinocytes seeded on opposite sides of bilayered matrix of bovine collagen. There are limited clinical data available for this product, but large clinical trials are ongoing. Limited data are also available for 2 types of dressing material derived from pigs: porcine small intestinal submucosa acellular collagen matrix (Oasis) and an acellular xenogeneic collagen matrix (E-Z-Derm). Both products have a long shelf life. Other novel skin substitutes are being investigated. The potential risks and benefits of using tissue-engineered skin need to be further evaluated in clinical trials but it is obvious that they offer a new option for the treatment of wounds.

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