1. The Second Department of Neurosurgery, Xingtai People's Hospital, Xingtai, Hebei 054031, P.R. China
2. Department of Neurosurgery, Tongchuan People's Hospital, Tongchuan, Shaanxi 727000, P.R. China
3. Department of Neurosurgery, Liaocheng People's Hospital, Liaocheng, Shandong 252004, P.R. China
4. Department of Neurosurgery, Taian City Central Hospital, Taian, Shandong 271000, P.R. China