This single-center, prospective, randomized controlled clinical trial aims to compare the postoperative analgesic efficacy of PENG block with or without posterior pericapsular deep gluteal block in adult patients undergoing elective primary total hip arthroplasty under spinal anesthesia. Total hip arthroplasty is commonly associated with moderate to severe postoperative pain. Although PENG block provides analgesia for the anterior hip capsule, some patients may still experience pain originating from the posterior capsule. The addition of PPD block may improve analgesia by targeting posterior articular branches. Participants will be randomized into two groups: one group will receive PENG block, and the other group will receive PENG plus PPD block. Postoperative pain will be assessed using the Numeric Rating Scale (NRS). The study will compare postoperative pain scores and other analgesia-related outcomes between groups.

This study is planned as a single-center, prospective, randomized, controlled, double-blind trial in adult patients undergoing elective primary total hip arthroplasty under spinal anesthesia. Eligible participants will be patients aged 18 years or older, classified as ASA physical status I-III, and able to provide informed consent. Patients with ASA IV-V, serious cardiac, respiratory, hepatic, or renal disease, neuropsychiatric disorders, cognitive impairment preventing reliable NRS assessment, coagulopathy, local anesthetic allergy, infection or scar at the block site, failed block, signs of local anesthetic systemic toxicity, exposure to local anesthetic doses above protocol limits, revision total hip arthroplasty, fracture-related total hip arthroplasty, or refusal to participate will be excluded. Participants will be randomized by sealed-envelope method into two groups. Group 1 will receive PENG block after spinal anesthesia in the supine position using ultrasound guidance and 20 mL of 0.25% bupivacaine. Group 2 will receive PENG block followed by ultrasound-guided PPD block, with 30 mL of 0.25% bupivacaine used for the PPD block. In addition, both groups will receive lateral femoral cutaneous nerve block with 5 mL of 0.25% bupivacaine. The primary objective is to compare postoperative pain intensity between groups using Numeric Rating Scale scores. Secondary evaluations include postoperative analgesic consumption, time to first rescue analgesia, time to first mobilization, and motor function including ankle dorsiflexion strength. An initial pilot phase including 40 patients is planned, and the final sample size will be calculated using G*Power based on pilot data with alpha 0.05 and power 0.80. The study will continue until the target sample size is reached.

Inclusion Criteria:

• Adults aged 18 years and older
• American Society of Anesthesiologists (ASA) physical status I-III
• Scheduled for elective primary total hip arthroplasty under spinal anesthesia
• Able to provide written informed consent

Exclusion Criteria:

• ASA physical status IV or V
• Serious concomitant cardiac, respiratory, hepatic, or renal disease
• Known neuropsychiatric disorder
• Cognitive impairment preventing understanding or response to the Numeric Rating Scale (NRS)
• Coagulopathy
• Local anesthetic allergy
• Infection or scar at the block site
• Failed block
• Refusal to participate
• Signs of local anesthetic systemic toxicity after block
• Patients in the PENG plus PPD group who would be exposed to a total local anesthetic dose above 3 mg/kg in patients weighing less than 50 kg
• Revision total hip arthroplasty
• Total hip arthroplasty planned for fracture

There is no plan to share individual participant data with other researchers