Total hip arthroplasty is a widely performed surgical procedure in the elderly population, aiming to relieve hip joint pain and restore function. Total hip arthroplasty is among the most critical surgical procedures in terms of morbidity and mortality within this demographic. To mitigate opioid-related adverse effects in this patient group, novel analgesic methods are needed. Regional anesthesia techniques used for postoperative pain management include epidural analgesia, lumbar plexus block, fascia iliaca block, femoral and obturator nerve blocks, and sacral erector spinae plane block. However, these procedures may result in complications such as epidural hematoma, postoperative headache, prolonged motor block, and extended hospital stay.

Total hip arthroplasty is a widely performed surgical procedure in the elderly population, aiming to relieve hip joint pain and restore function. Total hip arthroplasty is among the most critical surgical procedures in terms of morbidity and mortality within this demographic. To mitigate opioid-related adverse effects in this patient group, novel analgesic methods are needed. Regional anesthesia techniques used for postoperative pain management include epidural analgesia, lumbar plexus block, fascia iliaca block, femoral and obturator nerve blocks, and sacral erector spinae plane block. However, these procedures may result in complications such as epidural hematoma, postoperative headache, prolonged motor block, and extended hospital stay.

Recently, Tulgar et al. introduced a novel fascial plane block called the "quadro-iliac plane block". This block is performed in the quadro-iliac plane, located between the inner surface of the iliac crest and the posterior surface of the quadratus lumborum muscle. In their study, Tulgar et al. bilaterally injected 40 mL of methylene blue into the quadro-iliac plane, observing widespread dye distribution along the posterior and anterior surfaces of the quadratus lumborum muscle, transversalis fascia, ilioinguinal, iliohypogastric, subcostal, and genitofemoral nerves, as well as the lumbar plexus. Based on these findings, quadro-iliac plane block has been proposed as a potentially effective technique for managing acute or chronic pain in the lumbosacral, abdominal, and hip regions. However, apart from a few case reports involving lumbar spine surgery and kidney transplantation, evidence regarding the efficacy of quadro-iliac plane block remains limited.

Inclusion Criteria:

• Unilateral THA.
• Spinal anesthesia.
• Age 18-85 years.
• ASA classification I-IV.

Exclusion Criteria:

• Patients who declined consent.
• Contraindications to regional anesthesia.
• Coagulation disorders.
• Infections at the block site.
• Emergency surgeries.