[1] Hosp Clin Reg Univ Concepcion, Dept Neurosurg, Concepcion, Chile
[2] Univ Concepcion, Fac Med, Concepcion, Chile
[3] Univ Passo Fundo, Sao Vicente Paulo Hosp, Neurosurg, Passo Fundo, RS, Brazil
[4] Hosp Espanol Mendoza, Dept Orthoped, Spine Unit, Mendoza, Argentina
[5] ScienceRight Res Consulting, London, ON, Canada
[6] Hosp Univ Cajuru, Curitiba, Parana, Brazil
[7] Hosp Cristo Redentor, Dept Neurosurg, Porto Alegre, RS, Brazil
[8] Univ Campinas UNICAMP, Dept Neurosurg, Campinas, SP, Brazil
[9] Univ Desarrollo, Dept Orthoped & Traumatol, Santiago, Chile
[10] Clin Alemana, Dept Traumatol, Spine Unit, Santiago, Chile