1. Department of Spinal Cord Injury, General Hospital of Jinan Military Area Command of Chinese PLA, Jinan, Shandong, People's Republic of China
2. Department of Orthopedic Surgery, Orthopedics Oncology Institute of Chinese PLA, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi, People's Republic of China
3. Department of Baylor College of Medicine, Houston, Texas, USA