1. University Hospitalary Complex of Vigo, Instituto de Investigación Biomédica de Vigo; Vigo Spain
2. University Hospital Infanta Sofía; Madrid Spain
3. Sierrallana Hospi- tal; Torrelavega Spain
4. Institute for Musculoskeletal Health; Madrid Spain
5. University College London Hospital; London UK
6. Doctor Negrín University Hospital of Gran Canaria; Gran Canaria Spain