A scar is a mark left on the skin after a wound or injury has healed, for example, after surgery or after a burn. Most scars will fade and become paler over time, but some scars may become red and raised (called hypertrophic scars). Hypertrophic scars may take several years to flatten and fade.
Scars can be itchy, painful or unsightly, and may restrict movement. Scarring can affect people physically and emotionally, and can affect a person's well-being.
Treatments aim to improve a scar’s appearance and help to make it less visible. They include: wearing clothing that fits tightly around the skin (pressure garments); treatments applied to the scar; laser therapy and silicone gel sheets.
Silicone gel sheets are soft wound dressings containing an elastic form of silicone. They have a soft, rubbery texture and stick to the skin. They are commonly used on healing skin to help soften and flatten a hypertrophic scar.
What did we want to find out?
In this Cochrane Review, we wanted to find out how well silicone gel sheets worked in treating hypertrophic scars.
We searched for studies that investigated the use of silicone gel sheets to treat hypertrophic scars. We searched for randomised controlled trials only, in which the treatment each person receives is chosen at random. These studies give the most reliable evidence about the effects of a treatment.
What we found
We found 13 studies with 468 people (425 of them completed the study) with hypertrophic scars caused by surgery, injury, burns or scalding. The studies compared the effects of silicone gel sheets with: giving no treatment with silicone gel sheets; wearing pressure garments; applying silicone gel or onion extract; polyurethane dressings; steroid injections; laser therapy; intense pulsed light or Gecko Nanoplast (a silicone gel bandage).
All studies were conducted in hospitals, in Europe (6 studies), China (2), the USA (1), Canada (1), Iran (1), Turkey (1) and India (1). They lasted for different lengths of time: from 3 months to 12 months.
Four studies reported assessments of scars by healthcare professionals in way that was usable for this review. No studies reported useful results for the person's own assessment of their scar after treatment.
No studies reported useful results for people's well-being (quality of life): for whether people stayed on the treatment (adherence), whether the treatments had any unwanted effects; or whether the treatments were cost-effective (the benefits of treatment outweighed any extra costs).
The studies did not give enough information to compare silicone gel sheets with steroid injections, laser therapy or pulsed light.
What are the main results of our review?
Silicone gel sheets may slightly improve the appearance of hypertrophic scars compared with onion extract. We are uncertain whether silicone gel sheets improve a scar's appearance better than no treatment with silicone gel sheets, or silicone gel, or polyurethane.
Silicone gel sheets may reduce pain levels compared with pressure garments. Silicone gel sheets may also result in a slight reduction in pain levels compared with no treatment with silicone gel sheets. We are uncertain whether silicone gel sheets decrease pain compared with self-adhesive propylene glycol and hydroxyethyl cellulose sheeting. The evidence is also very uncertain about the effect of silicone gel sheets on pain compared with Gecko Nanoplast.
Certainty of the evidence
Our certainty (confidence) in the evidence was low, or very low. The evidence we found comes from a few studies (sometimes only one), often in small numbers of people, with poorly reported results, so we are not sure how reliable the results are. We therefore think our conclusions would be likely to change if results from further studies become available.
We are uncertain about whether silicone gel sheets work better than most other treatments for hypertrophic scars. Silicone gel sheets may improve the appearance of scars slightly compared with applying onion extract , and may reduce pain compared with no treatment with silicone gel sheets or pressure garments.
This review includes evidence published up to 21 April 2021.
There is currently limited rigorous RCT evidence available about the clinical effectiveness of SGS in the treatment of hypertrophic scars. None of the included studies provided evidence on severity of scarring validated by participants, health-related quality of life, or cost effectiveness. Reporting was poor, to the extent that we are not confident that most trials are free from risk of bias. The limitations in current RCT evidence suggest that further trials are required to reduce uncertainty around decision-making in the use of SGS to treat hypertrophic scars.
Each year, in high-income countries alone, approximately 100 million people develop scars. Excessive scarring can cause pruritus, pain, contractures, and cosmetic disfigurement, and can dramatically affect people's quality of life, both physically and psychologically. Hypertrophic scars are visible and elevated scars that do not spread into surrounding tissues and that often regress spontaneously. Silicone gel sheeting (SGS) is made from medical-grade silicone reinforced with a silicone membrane backing and is one of the most commonly used treatments for hypertrophic scars.
To assess the effects of silicone gel sheeting for the treatment of hypertrophic scars in any care setting.
In April 2021 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting.
We included randomised controlled trials (RCTs) that enrolled people with any hypertrophic scars and assessed the use of SGS.
Two review authors independently performed study selection, 'Risk of bias' assessment, data extraction and GRADE assessment of the certainty of evidence. We resolved initial disagreements by discussion, or by consulting a third review author when necessary.
Thirteen studies met the inclusion criteria. Study sample sizes ranged from 10 to 60 participants. The trials were clinically heterogeneous with differences in duration of follow-up, and scar site. We report 10 comparisons, SGS compared with no SGS treatment and SGS compared with the following treatments: pressure garments; silicone gel; topical onion extract; polyurethane; propylene glycol and hydroxyethyl cellulose sheeting; Kenalog injection; flashlamp-pumped pulsed-dye laser; intense pulsed light and Gecko Nanoplast (a silicone gel bandage). Six trials had a split-site design and three trials had an unclear design (resulting in a mix of paired and clustered data).
Included studies reported limited outcome data for the primary review outcomes of severity of scarring measured by health professionals and adverse events (limited data reported by some included studies, but further analyses of these data was not possible) and no data were reported for severity of scarring reported by patients. For secondary outcomes some pain data were reported, but health-related quality of life and cost effectiveness were not reported. Many trials had poorly-reported methodology, meaning the risk of bias was unclear. We rated all evidence as being either of low or very low certainty, often because of imprecision resulting from few participants, low event rates, or both, all in single studies.
SGS compared with no SGS
Seven studies with 177 participants compared SGS with no SGS for hypertrophic scars. Two studies with 31 participants (32 scars) reported severity of scarring assessed by health professionals, and it is uncertain whether there is a difference in severity of scarring between the two groups (mean difference (MD) -1.83, 95% confidence interval (CI) -3.77 to 0.12; very low-certainty evidence, downgraded once for risk of bias, and twice for serious imprecision). One study with 34 participants suggests SGS may result in a slight reduction in pain level compared with no SGS treatment (MD −1.26, 95% CI −2.26 to −0.26; low-certainty evidence, downgraded once for risk of bias and once for imprecision).
SGS compared with pressure garments
One study with 54 participants was included in this comparison. The study reported that SGS may reduce pain levels compared with pressure garments (MD −1.90, 95% CI −2.99 to −0.81; low-certainty evidence, downgraded once for risk of bias and once for imprecision).
SGS compared with silicone gel
One study with 32 participants was included in this comparison. It is unclear if SGS impacts on severity of scarring assessed by health professionals compared with silicone gel (MD 0.40, 95% CI −0.88 to 1.68; very low-certainty evidence, downgraded once for risk of bias, twice for imprecision).
SGS compared with topical onion extract
One trial (32 participants) was included in this comparison. SGS may slightly reduce severity of scarring compared with topical onion extract (MD -1.30, 95% CI -2.58 to -0.02; low-certainty evidence, downgraded once for risk of bias, and once for imprecision).
SGS compared with polyurethane
One study with 60 participants was included in this comparison. It is unclear if SGS impacts on the severity of scarring assessed by health professionals compared with polyurethane (MD 0.50, 95% CI -2.96 to 3.96; very low-certainty evidence, downgraded once for risk of bias, and twice for imprecision).
SGS compared with self-adhesive propylene glycol and hydroxyethyl cellulose sheeting
One study with 38 participants was included in this comparison. It is uncertain if SGS reduces pain compared with self-adhesive propylene glycol and hydroxyethyl cellulose sheeting (MD −0.12, 95% CI −0.18 to −0.06). This is very low-certainty evidence, downgraded once for risk of bias, once for imprecision and once for indirectness.
SGS compared with Gecko Nanoplast
One study with 60 participants was included in this comparison. It is unclear if SGS impacts on pain compared with Gecko Nanoplast (MD 0.70, 95% CI -0.28 to 1.68; very low-certainty evidence, downgraded once for risk of bias and twice for imprecision.
There was a lack of reportable data from the other three comparisons of SGS with Kenalog injection, flashlamp-pumped pulsed-dye laser or intense pulsed light.