Ultrasound-Guided Transmuscular Quadratus Lumborum Block Reduces Postoperative Pain Intensity in Patients Undergoing Total Hip Arthroplasty: A Randomized, Double-Blind, Placebo-Controlled Trial

METHODS: Eighty-eight patients undergoing THA were randomized to receive 0.33% ropivacaine (Group QLB, n = 44) or saline (Group Con, n = 44) for QL3 block. Spinal anesthesia was then performed. Pain intensity was assessed using the visual analog scale (0: no pain to 10: worst possible pain). The primary outcome was pain scores recorded at rest at 3, 6, 12, 24, 36, and 48 h and on standing and walking at 24, 36, and 48 h postoperatively. Secondary outcomes were analgesic consumption, side effects, the 10-meter walking speed on day 6, and patient satisfaction after surgery. RESULTS: Postoperative pain intensity was significantly lower in Group QLB compared to Group Con at rest after 3, 6, 12, 24, 36, and 48 h (p < 0.001) and during mobilization after 24, 36, and 48 h (p < 0.001). Morphine use was significantly lower in Group QLB compared to Group Con during 0–24 h (16.0 ± 7.1 vs. 34.1 ± 7.1 mg, p < 0.001) and during 24–48 h (13.0 ± 4.0 vs. 17.4 ± 4.6 mg, p < 0.001) postoperatively. The 10-meter walking speed was higher in Group QLB compared to Group Con, both at comfortable (0.79 ± 0.13 vs. 0.70 ± 0.14 m/s, p=0.012) and at maximum speeds (1.18 ± 0.26 vs. 1.06 ± 0.22 m/s, p < 0.001). Incidences of nausea (7.3% vs. 31%, p=0.006), vomiting (7.3% vs. 26.2%, p = 0.022), and urinary retention (9.8% vs. 28.6%, p=0.030) were lower in Group QLB than in Group Con. CONCLUSIONS: Ultrasound-guided QL3 block is an effective pain management technique after THA.