1. Department of Pediatric Orthopedics; Shengjing Hospital of China Medical University; No. 36 Sanhao Street, Heping District Shenyang 110004 China
2. Graduate School of Peking Union Medical College; Beijing 100730 China
3. National Research Institute for Family Planning; 12 Dahuisi Road Haidian Beijing 100081 China
4. Key laboratory of Health Ministry for Congenital Malformation; Shengjing Hospital of China Medical University; Shenyang 110004 China
5. Department of Pediatric Orthopedics; Red Cross Children's Hospital of Qingfeng; Qingfeng County Henan 457300 China