Characteristics of the included studies with description of intervention and control, risk factors for surgical site infections and level of contamination.

NR: not recorded. * unclear whether trial was single center or performed at two trial sites.Characteristics of the included studies with description of intervention and control, risk factors for surgical site infections and level of contamination.NR：未记录（not recorded）。* 尚不明确该临床试验为单中心开展，还是在两个试验中心实施。所纳入研究的特征信息包括：干预措施与对照方案的具体描述、手术部位感染（surgical site infections）的危险因素，以及污染程度分级。