1. Research Center for High Altitude Medicine, Qinghai University, Xining, Qinghai 810000, P.R. China
2. Department of Orthopaedics, The First People's Hospital of Xining City in Qinghai Province, Xining, Qinghai 810000, P.R. China
3. Public Health Department, Medical College, Qinghai University, Xining, Qinghai 810000, P.R. China