[1] Vrije Univ Amsterdam, Med Ctr, Dept Orthopaed Surg, NL-1081 HZ Amsterdam, Netherlands
[2] Toronto Western Hosp, Dept Surg, Toronto, ON M5T 2S8, Canada
[3] AOSpine Int, Res Dept, Davos, Switzerland
[4] Univ Sydney, George Inst, Musculoskeletal Div, Sydney, NSW 2006, Australia
[5] Istanbul Bilim Univ, Sch Med, Dept Orthopaed & Traumatol, Istanbul, Turkey
[6] Univ Calif San Francisco, Dept Orthopaed Surg, San Francisco, CA USA
[7] Univ Hong Kong, Dept Orthopaed & Traumatol, Hong Kong, Hong Kong, Peoples R China
[8] Hokkaido Univ, Grad Sch Med, Dept Orthopaed Surg, Sapporo, Hokkaido, Japan
[9] Washington Univ, Dept Orthopaed Surg, St Louis, MO USA
[10] Univ Minnesota, Dept Orthopaed Surg, Minneapolis, MN 55455 USA
[11] Nanjing Univ, Sch Med, Affiliated Drum Tower Hosp, Dept Spine Surg, Nanjing 210008, Jiangsu, Peoples R China
[12] Vrije Univ Amsterdam, Dept Hlth Sci, Amsterdam, Netherlands
[13] Univ Virginia, Dept Neurol Surg, Charlottesville, VA USA