Comparison of Ultrasound-Guided Erector Spinae Plane Block and Quadro-Iliac Plane Block in Elective Primary Unilateral Total Hip Arthroplasty

This prospective, single-center, randomized controlled, double-blind (participant and outcomes assessor) trial compares ultrasound-guided erector spinae plane block (ESPB) and quadro-iliac plane block (QIPB) in adult patients undergoing elective primary unilateral total hip arthroplasty (THA) under spinal anesthesia. Eighty patients will be randomized 1:1 to receive either block in addition to a standardized multimodal analgesia protocol. The primary outcome is cumulative opioid consumption (intravenous morphine equivalents, mg) during the first 24 postoperative hours. Secondary outcomes include quality of recovery (QoR-15), pain scores, opioid consumption at later time points, quadriceps strength, mobilization, patient satisfaction, and safety outcomes. It is hypothesized that QIPB will reduce 24-hour opioid consumption more than ESPB.

Inclusion Criteria: * Scheduled for elective primary unilateral total hip arthroplasty * Provided written informed consent * American Society of Anesthesiologists (ASA) physical status I, II or III * Aged 18-80 years * Scheduled to undergo surgery under spinal anesthesia * Able to understand the information provided in Turkish and have the cognitive capacity to complete the QoR-15 questionnaire Exclusion Criteria: * Contraindication to regional anesthesia (coagulopathy, inappropriate anticoagulant use, infection at the injection site, etc.) * History of known allergy or severe adverse reaction to local anesthetics * Chronic opioid use, opioid dependence, or history of substance abuse * Advanced cognitive impairment, inability to give valid consent, or inability to complete the questionnaires * Pregnancy or breastfeeding * Need for emergency surgery * Surgical plan extending beyond unilateral primary total hip arthroplasty (THA) * Presence of a severe systemic disease (severe neurological disease; advanced-stage hepatic, renal or cardiovascular failure) or clinical condition that may prevent adherence to the study protocol * Body mass index (BMI) \> 35 kg/m² * Contraindication or allergy to the multimodal analgesic agents specified in the protocol (paracetamol, NSAIDs, dexamethasone) or to morphine * Regular gabapentinoid use or chronic pain syndrome * Inability to use the patient-controlled analgesia (PCA) device