The effect of a pre- and post-operative orthogeriatric service on cognitive function in patients with hip fracture. The protocol of the Oslo Orthogeriatrics Trial oleh Wyller Torgeir, Watne Leiv, Torbergsen Anne, Engedal Knut, Frihagen Frede, Juliebø Vibeke, Saltvedt Ingvild, Skovlund Eva, Ræder Johan, Conroy Simon