Wigger‐Alberti 2009.

Methods	RCT
Participants	60 outpatients with hypertrophic scars: 16 men, 44 women; mean age 38.2 years; mean scar duration 49.6 months (range 3 to 35.5 months) Inclusion criteria: scars of > 6 weeks duration; scars 5 to 10 mm wide and 60 mm long (or greater) Exclusion criteria: keloid scars; "clinically significant illness"; history of hypersensitivity or adverse reactions to adhesive dressings; breastfeeding or pregnant women or women "trying to become pregnant"; scars having undergone any of the following treatments: radiotherapy; intralesional glucocorticosteroids (6 months prior to study); surgical treatments including laser therapy (2 months prior to the study); topical glucocorticosteroids (2 months prior to the study); or any other topical product (1 month prior to the study) Study location: 3 dermatological units in Germany (University Department of Dermatology, Leipzig; proDERM Institute for Applied Dermatological Research, Schenefeld/Hamburg; University Department of Dermatology, Kiel)
Interventions	silicone sheet or polyurethane dressing: silicone sheet changed once a week; polyurethane dressing changed daily; removal of dressings permitted up to 1 hour daily (recording of times/dates of treatment interruptions and reapplication) Each treatment applied to either half of one scar by random allocation Duration of treatments: 12 weeks
Outcomes	Percentage change in overall scar index (SI) from baseline to week 12 Percentage change in overall SI between baseline and weeks 4 and 8 Differences in overall SI (absolute change) between baseline, weeks 4, 8 and 12 Changes in skin redness (measured by chromametry) at weeks 4, 8 and 12: photographs on days 1 and 85 also Patient questionnaire (on day 85 of study only): modifications to test area (assessed on a 5‐point Likert scale: ‐1 as 'worsened'; 0 as 'unaltered'; 1 as 'improved'; to 3 as 'complete improvement' Assessments at: baseline; weeks 4, 8 and 12 ("every measurement was made in triplicate, and the average value was used")
Notes	67 participants recruited; 7 withdrew within first week of study "As all participants were outpatients, the study nurses also instructed them how to perform the remaining dressing changes at home. Patients were instructed how to apply the dressings properly and to replace them if they became loose" Participants instructed not to use adhesive tape with the polyurethane dressing "unless necessary"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The test product and the reference product were randomly allocated to one half of each treatment site by means of a randomisation list generated by the trial statistician" Comment: randomisation was judged to be adequate
Allocation concealment (selection bias)	Unclear risk	Comment: no information on allocation concealment was given in the study which we judged to be at unclear risk
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "to partially blind the study, the dressings were applied and removed in each test centre by a study nurse in the investigator's absence." Comment: participants not blinded due to "the difference in dressing appearance"
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: percentage change in overall scar index (SI) from baseline to week 12: "performed observer blind". Unclear from study report if other assessments were 'blinded': i.e. percentage change of overall SI between baseline, weeks 4 and 8; overall SI (absolute change) across all time points; changes in skin redness
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Two patients withdrew from the study on day 1 (one withdrew consent and one was lost to follow up).Five of the remaining 65 patients withdrew consent before the first assessment in week 4 (withdrawal of consent). The remaining 60 patients comprised the ITT population. However, five of these 60 patients terminated the study prematurely between days 29 and 85: three for personal reasons and two due to an allergic reaction, which may have been related to the silicone dressing." Comment: 12 participants lost in total; ITT performed. We judged attrition bias to be low.
Selective reporting (reporting bias)	Low risk	Comment: the study protocol was not sought, however all measurements discussed in the methods are reported in the results and clinically meaningful outcomes presented.
Other bias	Low risk	Comment: the study appears to be free from other sources of bias