Background and Objectives High-dose intravenous dexamethasone reduces the postoperative opioid requirement and is often included in the multimodal analgesia strategy after total knee arthroplasty (TKA). Combined obturator nerve and femoral triangle blockade (OFB) reduces the opioid consumption and pain after TKA better than local infiltration analgesia (LIA). The question is whether preoperative high-dose intravenous dexamethasone would cancel out the superior analgesic effect of OFB compared with LIA. The aim was to evaluate the analgesic effect of OFB versus LIA after TKA when all patients received high-dose intravenous dexamethasone.

Methods Eighty-two patients were randomly assigned either to OFB or LIA after primary unilateral TKA. All patients received 16 mg dexamethasone. Primary outcome was morphine consumption via patient-controlled analgesia during the first 20 postoperative hours. Secondary outcomes were pain, nausea, dizziness, and length of hospital stay.

Results Seventy-four patients were included in the analysis. Median total intravenous morphine consumption during the first 20 postoperative hours was 6 mg (interquartile range [IQR], 2–18 mg) in the OFB group and 20 mg (IQR, 12–28 mg) in the LIA group. The 14-mg difference (95% confidence interval, 6.4–18.0 mg) was significant (P < 0.001). There was no difference in pain score at rest at 20 hours postoperatively: 2 (IQR, 1–4) in the OFB group and 3 (IQR, 2–5) in the LIA group.

Conclusions Combined OFB reduces morphine consumption better than LIA after TKA even when all patients received high-dose intravenous dexamethasone.

Clinical Trial Registration This study was registered at ClinicalTrials.gov, identifier NCT02374008.