1. Department of Orthopaedics, Shengjing Hospital of China Medical University, Shenyang, China
2. Department of Clinical Epidemiology, Shengjing Hospital of China Medical University, Shenyang, China
3. Liaoning Women and Children's Health Hospital, Shenyang, China
4. Department of Science and Education, Shenyang Women and Children Health Care Centre, Shenyang, China
5. Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China