A randomised controlled trial comparing adductor canal block and femoral nerve block for knee arthroplasty.

Background: Adductor canal block (ACB) is hypothesised to provide superior analgesia to femoral nerve block (FNB) for total knee arthroplasty (TKA) while preserving quadriceps strength.

Methods: 30 patients undergoing TKA were randomised to receive either ACB or FNB. Baseline tests of quadriceps strength were performed. Ultrasound-guided blocks with 30 mL of 0.5% ropivacaine were administered before induction of general anaesthesia. Patient-controlled analgesia (morphine) was prescribed for postoperative analgesia. The primary outcome of this prospective, double-blinded, randomised controlled trial was morphine consumption (mean ± standard deviation) in the first 24 hours. Secondary outcomes were pain scores using a numeric rating scale (median and interquartile range [IQR]), quadriceps strength (% of baseline) and functional outcomes at 24 hours and 48 hours postoperatively.

Results: There was no statistically significant difference in morphine consumption at 24 hours between the ACB and FNB groups (21 ± 11 mg vs. 20 ± 12 mg; p = 0.85). No statistically significant differences were observed between the ACB and FNB groups in pain scores at 24 hours (at rest: 0 [IQR 0-2] vs. 0 [IQR 0-2]; on movement: 5 [IQR 4-8] vs. 5 [IQR 3-8]) and quadriceps strength (24 hours: 28.8% ± 26.1% vs. 26.8% ± 19.6% of baseline; 48 hours: 31.5 ± 23.1% vs. 33.7% ± 20.1% of baseline). There were also no statistically significant differences in functional outcomes and length of stay.

Conclusions: We found no statistically significant differences in analgesic effects, quadriceps strength or functional recovery postoperatively between ACB and FNB.