1. Universidade Federal de São Paulo; Department of Orthopaedics and Traumatology; R. Borges Lagoa, 783 - 5º Andar ? Vila Clementino São Paulo Brazil 04032-038
2. Escola Paulista de Medicina; São Paulo Brazil
3. University Medical Center Groningen, University of Groningen; Department of Epidemiology; Hanzeplein (Entrance 24) Groningen Groningen Netherlands PO Box 30.001, 9700 RB
4. Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University; Monash Department of Clinical Epidemiology, Cabrini Institute; 4 Drysdale Street Malvern Victoria Australia 3144