The analgesic efficacy of anterior femoral cutaneous nerve block in combination with femoral triangle block in total knee arthroplasty: a randomized controlled trial.

Background: Ultrasound-guided femoral triangle block (FTB) can provide motor-sparing anterior knee analgesia. However, it may not completely anesthetize the anterior femoral cutaneous nerve (AFCN). We hypothesized that an AFCN block (AFCNB) in combination with an FTB would decrease pain during movement in the immediate 12 h postoperative period compared with an FTB alone.

Methods: Eighty patients scheduled to undergo total knee arthroplasty were randomized to receive either FTB alone (FTB group) or AFCNB with FTB (AFCNB + FTB group) as part of the multimodal analgesic regimen. The primary outcome was pain during movement at 12 h postoperatively. Secondary outcomes included numeric rating scale (NRS) pain scores, incidence of surgical incision site pain, intravenous morphine consumption, immediate functional performance, patient satisfaction, and length of hospital stay.

Results: The NRS pain scores on movement 12 h postoperatively were significantly lower in the AFCNB + FTB group than in the FTB group (mean difference: -2.02, 95% CI: -3.14, -0.89, P < 0.001). The incidence of pain at the surgical incision site at 24 h postoperatively and morphine consumption within 48 h postoperatively were significantly lower (P < 0.001), and quadriceps muscle strength at 0° immediately after surgery was significantly greater in the AFCNB + FTB group (P = 0.04).

Conclusions: The addition of ultrasound-guided AFCNB to FTB provided more effective analgesia and decreased opioid requirement compared to FTB alone after total knee arthroplasty and may enhance immediate functional performance on the day of surgery.