[1] Univ Toronto, Dept Neurosurg, St Michaels Hosp, 36 Queen St, Toronto, ON M5B IW8, Canada
[2] Hosp Espanol Mendoza, Dept Orthoped, Mendoza, Argentina
[3] St Marys Hosp, Paley Orthoped & Spine Inst, W Palm Beach, FL USA
[4] Univ Calif Oakland, UCI Med Ctr, Oakland, CA USA
[5] Univ Estadual Campinas, Dept Neurosurg, Campinas, SP, Brazil
[6] Univ Passo Fundo, Sao Vicente Paulo Hosp, Dept Neurosurg, Passo Fundo, RS, Brazil
[7] Univ Buenos Aires, Hosp Clin, Dept Neurosurg, Buenos Aires, DF, Argentina
[8] Hosp Clin Reg Concepcion, Dept Neurosurg, Concepcion, Chile
[9] Great Ormond St Hosp Sick Children, Dept Orthopaed, London, England