Chao Liu1, Zhiyang Mo2, Qinghong Bi3, Liang Li4. 1. Department of Plastic Surgery, Shijiazhuang People's Hospital, Shijiazhuang, 050000, Hebei, China. 2. Department of Plastic Surgery, Qinghai Provincial People's Hospital, Xining, 810000, Qinghai, China. 3. Department of Obstetrics and Gynecology, Zibo Maternal and Child Health Hospital, Zibo, 255000, Shandong, China. 4. Department of Burn and Plastic Surgery, Zibo Central Hospital, Zibo, 255000, Shandong, China. zxyyllys@126.com.