1. School and Hospital of Stomatology, Lanzhou University, No. 222 Tianshui South Road, Chengguan District, Lanzhou 730000, Gansu, P. R. China
2. Key Laboratory of Mechanics on Disaster and Environment in Western China, Ministry of Education, College of Civil Engineering and Mechanics, Lanzhou University, No. 222 Tianshui South Road, Chengguan District, Lanzhou 730000, Gansu, P. R. China
3. Department of Orthopedics, Lanzhou University Second Hospital, No. 82 Cuiyingmen Street, Lanzhou 730030, Gansu, P. R. China