1. Department of Orthopaedics, Qingdao No. 6 People's Hospital, Qingdao, Shandong 266033, P.R. China
2. Department of Functional Examination, Qingdao Haici Medical Group, Qingdao, Shandong 266033, P.R. China
3. Department of Anesthesiology, Qingdao No. 6 People's Hospital, Qingdao, Shandong 266033, P.R. China