Continuous quadratus lumborum block and femoral nerve block for total hip arthroplasty: a randomized study

Background Continuous femoral nerve block (FNB) has been effectively used after total hip arthroplasty (THA). Recently the anterior approach to quadratus lumborum block (QLB) has been shown to produce postoperative pain relief after THA. Continuous QLB would benefit from a catheter insertion site that is farther away from the surgical site compared with continuous FNB. In this randomized controlled study, we compared analgesic effects of the two techniques in patients undergoing THA. Methods Thirty patients undergoing THA were randomly allocated into two groups receiving continuous QLB and FNB. Under ultrasound guidance, QLB and FNB were conducted before general anesthesia using 0.25% levobupivacaine 30 ml and 0.5% levobupivacaine 15 ml, respectively, and a catheter was introduced. Postoperatively, all patients received continuous infusion of 0.125% levobupivacaine at 4 ml/h. Postoperative measurements included visual analog scale (VAS) pain scores at rest and on movement, postoperative analgesic demands, cutaneous sensory blockade and adverse events for 48 h. Results Six patients were excluded and 24 patients (13 and 11 patients in QLB group and FNB, respectively) were analyzed. VAS scores on movement at 6 h [median (IQR): 67 (41-80) and 38 (22-41) in QLB and FNB groups, respectively, p = 0.008] and 24 h [60 (40-80) and 39 (28-64) in QLB and FNB groups, respectively, p = 0.018] were lower with FNB than with QLB. QLB did not produce consistent cutaneous sensory blockade. Conclusions Analgesic effects of continuous QLB were inferior to those of continuous FNB in patients undergoing THA under the current study condition.