• Yuying Qian, Zhiyuan Guo, Juanjuan Huang, Qunying Zhang, Xiaofeng An, Huansheng Hu, Fengqin Zhu, and Xianghe Wang.
• The 98th Clinical College of PLA, Anhui Medical University, Huzhou City, Zhejiang.
• Clin J Pain. 2020 Apr 1; 36 (4): 260-266.

Background And ObjectivesThe knee is innervated by the femoral, obturator, and sciatic nerves. An infrainguinal fascia iliaca compartment block (FICB) is often used as a technique for pain management after hip and knee arthroplasty. This approach blocks the femoral nerve, lateral femoral cutaneous nerve, and obturator nerve. Previous studies show suprainguinal FICB achieves improved postoperative analgesia compared with infrainguinal FICB after hip fracture. However, the analgesic effects of suprainguinal or infrainguinal FICB on the obturator nerve after total knee arthroplasty (TKA) remain to be established. This study compared the efficacy of suprainguinal versus infrainguinal FICB for the blockade of the obturator nerve using electromyography and quantification of total opioid consumption during the 24 hours after TKA.MethodsThis prospective, randomized controlled clinical study enrolled 74 patients scheduled to undergo TKA. Patients were randomized 1:1 to receive suprainguinal FICB (group S) or infrainguinal FICB (group I) with 30 mL of 0.375% ropivacaine. The primary endpoint was the mean amplitude of the adductor longus compound muscle action potential (CMAP) at 0 (before the block), 10, 20, and 30 minutes after FICB. The secondary endpoint was total opioid consumption during the 24 hours after TKA.ResultsData from 62 patients were included in the analysis. The mean amplitude of the adductor longus CMAP was significantly lower in group S compared with group I (repeated-measures analysis of variance; F=4.73, P=0.034). At 24 hours after TKA, mean (SD) total opioid consumption was significantly lower in group S, compared with group I (131.5±76.8 vs. 201.5±85.1 μg) (P=0.001).ConclusionsSuprainguinal FICB significantly increased the incidence of successful obturator nerve block and significantly decreased fentanyl consumption 24 hours after TKA compared with infrainguinal FICB.

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