To evaluate the efficacy of transcranial direct current stimulation (tDCS) in reducing the incidence of postoperative delirium (POD) in elderly patients undergoing hip fracture surgery.

This single-center, double-blind, randomized controlled trial will enroll participants aged 65 years and older, scheduled for elective hip surgery under spinal anesthesia. Participants will be randomly assigned to either the active-tDCS group or the sham-tDCS group. The active-tDCS group will receive two sessions: one pre-surgery and one post-surgery, with electrodes positioned over the left dorsolateral prefrontal cortex and the right supraorbital area. Each session includes 15-second ramp-up phase at the start, 20 minutes simulation with 2 mA current and 15-second ramp-down phase at the end. The sham-tDCS group will receive two sham procedures with no actual current delivered. Functional brain activity will be monitored before and after each session or sham procedure to assess changes in cortical activation and connectivity using functional near-infrared spectroscopy (fNIRS). The primary outcome measure will be the incidence of POD, assessed using the 3-Minute Diagnostic Interview for Confusion Assessment Method (3D-CAM). Secondary outcomes include the severity of delirium, postoperative pain, anxiety, depression, cognitive function, and sleep quality.

1. Screening The trial staff will review orthopedic inpatient registration lists and elective surgery application forms to identify adults aged 65 years and older scheduled for surgical repair of clinically or radiologically diagnosed femoral neck, intertrochanteric, or subtrochanteric hip fractures. Potential participants will be screened for eligibility based on inclusion and exclusion criteria, which will be assessed through medical record reviews and face-to-face interviews.
2. Specific intervention The standard intervention consists of two sessions of tDCS and four sessions of fNIRS. The tDCS sessions will be administered on the day of surgery: the first session will be conducted preoperatively and the second session will take place postoperatively in the PACU. The fNIRS assessments will be performed as part of the monitoring protocol at four designated time points throughout the study.
3. Four fNIRS procedures will be conducted in relation to the tDCS interventions: (1) f1 (pre first tDCS) will be conducted before the first tDCS session; (2) f2 (post first tDCS, pre-surgery) will be conducted after the first tDCS session and before surgery; (3) f3 (post-surgery, before second tDCS) will be conducted after surgery and before the second tDCS session; (4) f4 (post second tDCS) will be conducted after the second tDCS session.

The primary outcome measure will be the incidence of POD, assessed using the 3-Minute Diagnostic Interview for Confusion Assessment Method (3D-CAM). Secondary outcomes include the severity of delirium, postoperative pain, anxiety, depression, cognitive function, and sleep quality.

Inclusion Criteria:

(1) aged ≥ 65 years; (2) scheduled for elective hip fracture, including femoral head fractures, femoral neck fractures, intertrochanteric or subtrochanteric fractures, femoral head replacement, total hip arthroplasty, or open or closed reduction; (3) platelet count > 80 × 10⁹/L; (4) ASA classification ≤ Grade III; (5) Mini-Mental State Examination (MMSE) scores ≥ 18 points (13); (6) willingness to participate and sign the informed consent form.

Exclusion Criteria:

(1) severe mental disorders,(e.g,depression or schizophrenia requiring medication treatment); (2) cranial or scalp injuries; (3) history of symptomatic cerebrovascular disease, including stroke, transient ischemic attack; (4) compound injuries, multiple fractures, periprosthetic fractures, and hip joint revisions; (5) drug or alcohol abuse; (6) severe visual or hearing impairments; (7) history of epilepsy or intracranial metal implants; (8) severe cardiovascular disease history and liver dysfunction, or kidney dysfunction; (9) coagulation abnormalities; (10) severe chronic obstructive pulmonary disease; (11) participation in other clinical studies within the past 3 months.

Paper case report forms were written by hand

All participants will remain blinded to their group assignment. Surgeons, anesthesiologists, and ward and operating room nurses will also be blinded to the group allocations and intervention protocols. Additionally, personnel involved in outcome assessment, follow-up, data collection, and data processing will remain blinded to both the intervention protocols and group assignments.