摘要Background:Scar contractions caused by trauma or burns can cause secondary physical dysfunction and disfig-urement.Many minimally invasive methods for scar contraction have shown limited applicability and efficacy.This study investigated the feasibility and efficacy of intralesional collagenase injections for scar contraction treatment.Methods:Patients with contracted scars who had limited joint movement and physical disfiguration for＞1 year were enrolled in this single-blind,randomized clinical trial from July 2017 to February 2018 at Shanghai Ninth People's Hospital.Collagenase was injected into the firm-contracted scar(15 U/cm2)three times at 4-week in-tervals in the multiple treatment group and once in the single treatment group,and a placebo injection was performed in the control group.Scar length and skin texture were documented at the 4-and 12-week follow-ups.The safety of the collagenase treatment was also evaluated.Results:The contracted scar was significantly elongated after both single and multiple collagenase treatments.The results showed that,compared to a one-time treatment,repeated injections were more effective at 12 weeks,with an average improvement of 26.83(15.79％).At 12 weeks,78.9％of the patients in the multiple group and 52.9％in the single group achieved significant improvement at 12 weeks.No severe adverse events were observed.Conclusion:Intralesional collagenase injection showed promising results in improving scar contraction and pro-vides an alternative treatment for patients.Trial registration:ChiCTR,ChiCTR-IIR-16009910.Registered November 18,2016.Prospective registration,https://www.chictr.org.cn/showproj.html?proj=16853.