Postoperative delirium is a significant and commonly encountered complication in patients undergoing hip surgery, particularly among the elderly. Postoperative delirium is associated with serious consequences, including prolonged intensive care unit stay, increased complication rates, higher mortality risk, and rising healthcare costs.

The incidence of Postoperative delirium after hip fracture surgery has been reported to range between 13% and 55.9%, indicating a substantial clinical burden.

Effective postoperative pain control is critical not only for maintaining quality of life but also for preserving cognitive well-being. In this context, peripheral nerve blocks are frequently used for pain management following hip surgery.

Postoperative delirium is a significant and commonly encountered complication in patients undergoing hip surgery, particularly among the elderly. Postoperative delirium is associated with serious consequences, including prolonged intensive care unit stay, increased complication rates, higher mortality risk, and rising healthcare costs.

The incidence of Postoperative delirium after hip fracture surgery has been reported to range between 13% and 55.9%, indicating a substantial clinical burden.

Effective postoperative pain control is critical not only for maintaining quality of life but also for preserving cognitive well-being. In this context, peripheral nerve blocks are frequently used for pain management following hip surgery.

In recent years, the Pericapsular Nerve Group block and the supra-inguinal fascia iliaca block have gained attention as regional anesthesia techniques that provide effective analgesia by targeting the nerve branches innervating the anterior capsule of the hip joint.

Inclusion Criteria:

• Patients aged 18-80
• ASA I-III risk groups
• Undergoing elective hip surgery

Exclusion Criteria:

• Preoperative history of delirium, dementia, or major neurological disease
• Present cognitive impairment or severe hearing or visual impairment that could affect pain assessment
• Development of mechanical ventilation requirement in the intensive care unit; Need for bilateral hip surgery
• Failure to provide meaningful analgesia after block application due to surgical pain outside the scope of the block
• Patient's inability to complete the pain diary during postoperative follow-up;
• Urgent hip surgery
• Voluntary failure to give consent or request to withdraw from the study.

We conducted a pilot study on 20 patients using the 'goodness-of-fit tests: contingency tables' test with G Power software. In our study, the incidence of rebound pain was 40%, and postoperative delirium developed in 50% of patients with rebound pain, compared to 8.3% in patients without rebound pain.

Based on these data, an effect size of 0.356 was found, and an analysis was conducted using α=0.05, 90% power.

The sample size was calculated as 83 patients. Considering the dropout rate, a total of 90 patients (36 patients with rebound pain and 54 patients without rebound pain) were calculated to be included in the study.