To observe whether preoperative olfactory training can reduces the incidence of postoperative delirium in elderly patients undergoing orthopedic surgeries, a prospective randomized controlled study method will be used in this study.

450 elderly patients undergoing orthopedic surgeries (hip or knee replacement and laminectomy) under general anesthesia or combined spinal epidural anesthesia will be selected. They will be randomly divided into control group and olfactory training group.The olfactory training group was performed 24-48h before surgery used phenylethyl alcohol (rose), phytol (press tree), citronella (lemon), eugenol (clove) 4 kinds of smell，twice a day for three days. The general condition, operation, anesthesia and hospitalization related data of the patients will be recorded.

Outcome Measures： Incidence of postoperative delirium: The 3D-CAM scores of the control group and the olfactory training group were evaluated within 1-5 days after operation.

Degree of delirium：The MDAS of the control group and the olfactory training group were evaluated within 1-5 days after operation.

Pain：The VAS of the control group and the olfactory training group were evaluated within 1-5 days after operation.

Olfactory function：The TDI scores of the control group and the olfactory training group were evaluated in 3 days before operation and 48h after operation.

Cognitive function：The MoCA scores of the control group and the olfactory training group were evaluated in postoperative 5-7 days.

Markers: Delirium related markers and inflammatory factors in bloods was detected before surgery and after anesthesia. Delirium related markers and inflammatory factors in cerebrospinal fluid was detected after spinal puncture.

Subgroup analysis: patients were divided into delirium group and non-delirium group according to whether delirium occurred, and the data of the two groups were compared, including preoperative and postoperative olfactory function TDI scores, preoperative and postoperative VAS scores, nutritional scores, activity scores, and frailty index, Carlson comorbidity index, depression, anxiety state, sleep disturbance, etc., to screen risk factors.

Inclusion Criteria:

1. Patients undergoingorthopedic surgeries (hip or knee replacement and laminectomy) under general anesthesia or combined spinal-epidural anesthesia:
2. 65 years old ≤ age ≤ 90 years old, gender is not limited, ASA classification ≤ class III:
3. There is no recent history of surgery, and the operation time is ≥ 2 hours.
4. Able to communicate normally, able to cooperate and complete the cognitive function test. MMSE score >17.
5. Patients and their families are aware of and willing to participate.

Exclusion Criteria:

1. emergency surgery;
2. People with brain diseases or history of brain diseases such as cerebral infarction, stroke, etc.:
3. Have a history of neurological and psychological diseases, including Alzheimer's disease, Parkinson's, psychosis, etc.:
4. Illiteracy, severe hearing or visual impairment;
5. Those who have taken psychotropic drugs or abused psychotropic drugs within one month:
6. Sinusitis, previous nasal surgery history, nasal congestion, upper respiratory tract infection in the past two weeks, previously diagnosed rhinitis and other diseases that may affect olfactory function.
7. Patients who are allergic to pollen
8. Patients who cannot cooperate or refuse to sign informed consent

In this study, different researchers will be responsible for randomization, olfactory training, anesthesia and visit. Due to the peroperative olfactory training in the olfactory training group, it is impossible to blind the participant and researchers implementing olfactory training.A researcher is responsible for assigning random numbers to ensure the randomness of the study groups. In order to ensure that the whole study is not affected by subjective factors, the researchers implementing and visiting are blinded, who do not know the anesthesia grouping, and are responsible for anesthsia, case enrollment screening, signing informed consent, preoperative and postoperative delirium evaluation, postoperative pain evaluation, complications and safety evaluation.