Effects of olfactory enrichment on perioperative neurocognitive disorders in elderly patients undergoing orthopedic surgery: a study protocol of a multi-center randomized controlled trial. - Mei, Xinchun; Wang, Jiayi; Ni, Zihan; Wang, Yanyan; Zhao, Binglei; Sessler, Daniel I.; Xie, Zhongcong; Shen, Yuan (Trials, 2025)