1. Department of Spinal Surgery, Qingdao Huangdao Central Hospital, Qingdao University Medical Group, Qingdao 266555, P. R. China
2. College of Chemistry and Chemical Engineering, Qingdao University, 266071 Qingdao, P. R. China
3. The Department of Plastic Surgery, Lanzhou University Second Hospital, Lanzhou University, Lanzhou 730030, P. R. China
4. Department of Spinal Surgery, Affiliated Hospital of Qingdao University, Qingdao 266071, P. R. China