1. Department of Orthopedics, Hospital Español, Mendoza, Argentina,
2. Department of Orthopedics, Hospital Churruca Visca, Argentina
3. Department of Neurosurgery, Hospital Clinico Regional, Concepcion, Chile,
4. Department of Neurosurgery, Hospital Español de La Plata, La Plata, Argentina
5. Department of Orthopedics, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina,
6. Department of Neurosurgery, University of Caxias do Sul, Caxias do Sul, Rio Grande do Sul, Brazil.