1. Department of Orthopedics, Sixth Medical Center of the PLA General Hospital, Beijing 100048, P.R. China
2. Community Health Service Center of South Railway Station, Chengdu, Sichuan 610042, P.R. China
3. Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China