1. Department of Pain, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, P.R. China
2. Department of Pain, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan 637002, P.R. China
3. Department of Pain, Guizhou Provincial People's Hospital, Guiyang, Guizhou 550002, P.R. China
4. Department of Orthopedic Surgery, First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan 650032, P.R. China