1. Department of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Capital Medical University, Beijing 100035, China
2. Department of Epidemiology and Biostatistics, Beijing Research Institute of Traumatology and Orthopaedics, Beijing Jishuitan Hospital, Capital Medical University, Beijing 100035, China
3. Department of Medical Experimental Technology, School of Public Health, North China University of Science and Technology, Tangshan, Hebei 063210, China.