Spanish National Hip Fracture Registry (SNHFR): a description of its objectives, methodology and implementation by Sáez-López, P, González-Montalvo, J, Ojeda-Thies, C, Mora-Fernández, J, Muñoz-Pascual, A, Cancio, J, Tarazona, F, Pareja, T, Gómez-Campelo, P, Montero-Fernández, N, Alarcón, T, Mesa-Lampre, P, Larrainzar, R, Duaso, E, Gil-Garay, E, Diéz-Pérez, A, Prieto-Alhambra, D, Queipo-Matas, R, Otero-Puime, A