Postoperative analgesic efficacy of femoral nerve block versus adductor canal block in patients undergoing knee arthroscopy A quasi-experimental, single-center study.

Abstract

Introduction: Postoperative pain after total knee arthroplasty (TKA) is a major clinical challenge that delays rehabilitation and compromises recovery quality. Peripheral nerve blocks are crucial components of multimodal analgesia; however, the optimal technique to balance pain relief and motor preservation remains under debate. This study aimed to compare the postoperative analgesic efficacy of ultrasound-guided femoral nerve block (FNB) versus adductor canal block (ACB) in patients undergoing TKA at Hospital Alcívar.

Materials and Methods: A prospective, quasi-experimental study was conducted during 2025. Thirty patients (aged 35–75, ASA I–III) undergoing TKA were included and allocated to two groups (n=15 each). Group 1 received an ultrasound-guided FNB, and Group 2 received an ultrasound-guided ACB, both using 20 mL of 0.25% bupivacaine. Postoperative pain intensity was evaluated using the Visual Analog Scale (VAS) at 6 and 12 hours. Secondary outcomes included the requirement for intravenous rescue analgesia and the rate of assisted ambulation at 24 hours. Statistical significance was set at P < 0.05.

Results: The sample showed demographic homogeneity in mean age (63 ± 7 years for FNB vs. 64 ± 9 years for ACB; P=0.678) and sex distribution (P=0.715). No statistically significant differences were observed in pain perception between groups at 6 hours (P=0.9214) or 12 hours (P=0.654), with most patients achieving optimal pain control (VAS 0–3). Intravenous rescue analgesia requirements were similarly low between groups (33.3% for FNB vs. 20% for ACB; P=0.409). Assisted ambulation at 24 hours reached high rates in both arms; although ACB showed a higher absolute success rate (93.3% vs. 80.0%), this difference did not reach statistical significance (P=0.283).

Conclusions: Ultrasound-guided ACB provides postoperative analgesia equivalent to FNB for total knee arthroplasty, maintaining low opioid consumption and excellent immediate pain control. Although no statistically significant superiority was found in functional mobility, ACB demonstrates a positive clinical trend toward earlier ambulation. These findings support preferential implementation of ACB within Enhanced Recovery After Surgery (ERAS) protocols to optimize patient safety and hospital workflow.