Total hip arthroplasty (THA) causes moderate-to-severe postoperative pain. The PROSPECT guideline recommends the supra-inguinal fascia iliaca compartment block (SI-FICB) for THA, whereas evidence for newer quadratus-lumborum-family blocks is limited. The quadro-iliac plane block (QIPB) is a recently described fascial plane block, and no study has compared QIPB with SI-FICB head-to-head in any surgical context. In this prospective, double-blind, patients undergoing elective THA who receive one of the two routinely used preoperative blocks (SI-FICB or QIPB, chosen by the attending anesthesiologist as part of routine care) are systematically observed and compared. The primary objective is to assess whether the postoperative analgesic efficacy of QIPB is non-inferior to SI-FICB, using the resting NRS pain score at 6 hours postoperatively as the primary endpoint (non-inferiority margin Δ = 1.3).