This randomized, double-blinded, controlled clinical trial compares three motor-sparing regional anesthesia techniques used for postoperative analgesia in patients undergoing hip arthroplasty: the Pericapsular Nerve Group (PENG) block, the suprainguinal Fascia Iliaca Compartment Block (S-FICB), and the Lumbar Erector Spinae Plane Block (L-ESPB). Although all three techniques are widely used in modern hip surgery, their relative analgesic efficacy, opioid-sparing potential, and impact on early functional recovery have not been directly compared in a single study.

The primary objective is to determine which block provides the most effective postoperative analgesia while preserving motor function and facilitating early mobilization. Secondary objectives include comparisons of opioid consumption, pain scores at rest and during movement, time to first rescue analgesia, block-related adverse events, quadriceps strength, incidence of postoperative nausea and vomiting, and early functional outcomes.

This study aims to identify the optimal motor-sparing regional anesthesia strategy for older adults undergoing hip arthroplasty.

Regional anesthesia plays a key role in modern multimodal analgesia for hip arthroplasty, particularly in older adults who are vulnerable to opioid-related adverse effects and postoperative functional decline. Several motor-sparing nerve block techniques have been developed to improve postoperative pain control while maintaining quadriceps strength and enabling early mobilization. Among them, the Pericapsular Nerve Group (PENG) block, the suprainguinal Fascia Iliaca Compartment Block (S-FICB), and the Lumbar Erector Spinae Plane Block (L-ESPB) are widely used in clinical practice. However, no randomized clinical trial has directly compared these three approaches within a single study population.

The PENG block targets the articular branches of the femoral, obturator, and accessory obturator nerves, providing selective analgesia of the anterior hip capsule with minimal motor involvement. The suprainguinal FICB delivers a higher spread of local anesthetic over the femoral nerve, lateral femoral cutaneous nerve, and variable portions of the obturator nerve, offering broader sensory coverage but with a higher likelihood of quadriceps weakness. The lumbar ESPB is a posterior fascial plane block that may achieve indirect spread toward the lumbar plexus, potentially providing balanced anterior and posterior capsular analgesia while preserving motor function.

This randomized, double-blinded, three-arm controlled trial aims to compare the analgesic effectiveness, opioid-sparing properties, and motor-sparing characteristics of PENG, S-FICB, and L-ESPB in patients undergoing hip arthroplasty. All participants will receive standardized spinal anesthesia and multimodal postoperative analgesia. The study's primary endpoint is the time to first rescue opioid administration. Secondary outcomes include total postoperative opioid consumption, pain scores at rest and during movement, quadriceps muscle strength, block performance time, incidence of postoperative nausea and vomiting, early mobilization parameters, and block-related adverse events.

The results of this trial are expected to clarify the relative benefits and limitations of the three most commonly used motor-sparing regional anesthesia techniques for hip surgery and to guide optimal selection of blocks for enhanced recovery pathways in older adults undergoing hip arthroplasty.

Inclusion Criteria:

• Adults aged 65 years or older scheduled to undergo elective hip arthroplasty under spinal anesthesia.
• Ability to provide written informed consent.
• Ability to understand and reliably use numerical pain assessment tools (NRS 0-10).
• ASA physical status II-III.
• Expected postoperative hospitalization of at least 48 hours to ensure complete data collection.

Exclusion Criteria:

• Inability to provide informed consent due to cognitive impairment, language barrier, or severe hearing/speech limitations.
• Coagulopathy or therapeutic anticoagulation not meeting safety criteria for regional anesthesia.
• Local infection at the planned block site.
• Allergy, hypersensitivity, or contraindication to ropivacaine, local anesthetics, or study medications.
• Pre-existing lower-limb neurological deficits (motor or sensory) affecting outcome assessments.
• Severe spinal deformity or anatomical limitations preventing safe performance of regional blocks.
• Chronic opioid use (defined as >30 mg oral morphine equivalents daily for more than 2 weeks).
• Severe renal failure (eGFR <30 mL/min/1.73m²) or severe hepatic impairment.
• Uncontrolled diabetes mellitus (fasting glucose >300 mg/dL or HbA1c >10%).
• History of local anesthetic systemic toxicity (LAST).
• Participation in another interventional clinical trial within the past 30 days.
• Any condition deemed by investigators to interfere with protocol adherence, safety monitoring, or outcome reliability.

De-identified individual participant data (IPD) underlying the primary and secondary outcome analyses will be made available to other researchers upon reasonable request. Shared data will include demographic variables, intraoperative information, block-related details, pain scores, opioid consumption, motor assessments, and adverse events. No direct identifiers or protected health information will be included.

IPD and supporting documents will become available 12 months after publication of the primary results and will remain accessible for 5 years.

Researchers must submit a methodologically sound proposal describing the intended use of the data. Requests will be reviewed by the study investigators. Data will be shared through secure, password-protected transfer methods. A data-sharing agreement will be required before access is granted.