Preoperative femoral nerve block reduces rebound pain after knee arthroplasty versus postoperative block

IntroductionThe number of total knee arthroplasties (TKA) is steadily increasing worldwide, exceeding 3 million cases annually. Postoperative pain affects over 60% of patients and is a major barrier to early recovery. Femoral nerve block (FNB) is widely used for analgesia in TKA. This study investigated whether the timing of FNB influences the incidence of rebound pain after TKA.MethodsIn this prospective randomized trial comparing two active interventions, 186 patients undergoing primary TKA were assigned to a pre-FNB group (FNB before surgery using 20 ml of 0.375% ropivacaine) or a post-FNB group (FNB after surgery with the same protocol). The primary outcome was rebound pain within 24 h postoperatively, assessed using the numerical rating scale (NRS). Secondary outcomes included intraoperative anesthetic consumption, nocturnal pain intensity (8–12 h postoperatively), chronic postoperative pain at 3 months, extubation time, post-anesthesia care unit (PACU) stay, Steward score at PACU discharge, number of patient-controlled analgesia (PCA) presses, length of hospital stay, and patient satisfaction before discharge.ResultsRebound pain occurred in 16.1% (15/93) of patients in the pre-FNB group and 31.2% (29/93) in the post-FNB group (P = 0.016; relative risk = 0.52, 95% confidence interval 0.30–0.90). Mean propofol and remifentanil consumption were significantly lower in the pre-FNB group (237.64 ± 99.40 mg vs. 368.98 ± 100.29 mg, and 0.65 ± 0.21 mg vs. 0.97 ± 0.28 mg, respectively; both P < 0.001). Nocturnal pain intensity was also lower in the pre-FNB group (P = 0.021).ConclusionPreoperative FNB significantly reduced rebound pain incidence, lowered intraoperative opioid use, and improved nocturnal pain control compared with postoperative FNB, which may contribute to enhanced recovery.