Objective: To determine whether adductor canal block (ACB) is non-inferior to femoral nerve block (FNB) in pain relief and whether ACB is superior to FNB in quadriceps strength after arthroscopic anterior cruciate ligament reconstruction (ACLR) with hamstring graft.

Materials and Methods: A blinded, randomized, non-inferiority trial was performed in patients undergoing ACLR with hamstring graft. They were randomly assigned ACB or FNB. The primary outcome was a non-inferiority comparison of visual analogue scale (VAS) pain scores (0 to 100 mm) within 24 hours post-operatively. The secondary outcomes were opioid consumption, opioidfree duration, quadriceps strength in percentage of body weight, ability to discharge, and opioid side effects. Non-inferiority margin of ACB to FNB was considered to be 50% of clinically significant difference (VAS 5 mm). Other outcomes were tested for superiority. The present trial was registered with the ClinicalTrials.gov, number NCT 02411890.

Results: Fifty-six patients were included in the present analysis. The ACB group reported higher VAS pain scores compared to the FNB group without significance at rest 5.67 (95% CI –3.46 to 14.79; p=0.224) and at activity 7.64 (95% CI –2.56 to 17.85; p=0.142). The ACB group had significantly better quadriceps strength at 8-hours post-operative compared to the FNB group with a mean difference of 5.84 (95% CI 2.13 to 9.54; p=0.002). No significant differences in morphine consumption, free opioid time, ability to discharge, and opioid side effects between the groups were found.

Conclusion: The present study could not indicate that ACB was non-inferior to FNB in post-operative pain reduction after arthroscopic ACLR with hamstring graft. ACB showed superior quadriceps strength in the early post-operative period.

Keywords: Adductor canal block, Femoral nerve block, Anterior cruciate ligament reconstruction, Post-operative analgesia