[1] Tianjin Med Univ, Tianjin, Peoples R China
[2] Nankai Univ, Sch Med, Tianjin, Peoples R China
[3] Tianjin Union Med Ctr, Dept Spinal Surg, Tianjin, Peoples R China
[4] Chengde Med Univ, Affiliated Hosp, Dept Spinal Surg, Chengde, Hebei, Peoples R China
[5] Nanyang Cent Hosp, Dept Orthoped, Nanyang, Henan, Peoples R China