1. Rheumatology Unit, Hospital Universitario Fundación Alcorcon, Alcorcon, Madrid, Spain
2. Department of Epidemiology and Public Health, Universidad Rey Juan Carlos, Madrid, Spain
3. Radiology Unit, Hospital Universitario Fundación Alcorcon, Madrid, Spain
4. Rheumatology Unit, Hospital Universitario La Paz, Madrid, Spain
5. Rheumatology Unit, Hospital Universitario Parc Taulí, Barcelona, Spain