Effects Of Ultrasound-guided Different Approaches Fascia Iliaca Compartment Block On The Electromyography Of Obturator Nerve

Background and Objectives: The knee is innervated by the femoral,obturator and sciatic nerves.Infrainguinal fascia iliaca compartment block(FICB)has been used to block the femoral nerve,the lateral femoral cutaneous nerve,and the obturator nerve as pain management after hip and knee arthroplasty.Previous studies show suprainguinal FICB achieves improved postoperative analgesia compared to infrainguinal FICB after hip fracture.However,the analgesic effect of suprainguinal and infrainguinal FICB on the obturator nerve after total knee arthroplasty(TKA)remains controversial.This study compared the efficacy of suprainguinal and infrainguinal FICB for blockade of the obturator nerve based on electromyography and total opioid consumption during the 24 h after TKA.Methods: This prospective,double-blind,randomized controlled clinical study enrolled74 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 amplitude of adductor longus CMAPs were measured before blockade.The efficacy of obturator nerve block was evaluated by assessing changes in the amplitude of adductor longus CMAPs.Adductor longus CMAPs were monitored every 5 minutes for 30 minutes after FICB using electromyography.The mean amplitude of the adductor longus compound muscle action potential(CMAP)at 0(before block),10,20,and 30 min after FICB were recorded.The total opioid consumption during the 24 h after TKA were recorded.Statistical analysis:Statistical analyses were performed using SPSS Statistics(version 22.0).Continuous variables are reported as mean ± standard deviation(SD).Between-group comparisons of the amplitude of adductor longus CMAPs over the30-minunte period were evaluated with repeated measures analysis of variance.Between-group differences in total fentanyl consumption during the 24 h after TKA were assessed with the independent Student's t test.P < 0.05 was considered statistically significant.Results: Data from 62 patients were included in the analysis.Mean amplitude of the adductor longus CMAP was significantly lower in Group S compared to Group I(repeated measures analysis of variance;F = 4.73,P = 0.034)during the 30 minutes after block.Before block,there were no significant differences in the mean amplitude of adductor longus CMAPs between Group S and Group I(P = 0.0557,LSD-t test).10 minutes after block,there were no significant differences in the mean amplitude of adductor longus CMAPs between Group S and Group I(P = 0.182,LSD-t test).20 minutes after block,the mean amplitude of the adductor longus CMAP was significantly lower in Group S(602.5 ±343.2?V)compared to Group I(894.2 ±449.6?V)(P=0.006,LSD-t test).30 minutes after block,the mean amplitude of the adductor longus CMAP was significantly lower in Group S(482.5 ±295.5?V)compared to Group I(869.0 ±461.1?V)(P < 0.001,LSD-t test).At 24 h after TKA,mean(SD)total opioid consumption was significantly lower in Group S compared to Group I(131.5±76.8?g versus 201.5±85.1?g)(P = 0.001).Conclusions: Ultrasound-guided suprainguinal FICB and infrainguinal FICB both decreased the amplitude of of adductor longus CMAPs,but suprainguinal FICB significantly decreased the amplitude of of adductor longus CMAPs,and significantly decreased fentanyl consumption 24 hours after TKA compared to infrainguinal FICB.Therefore,we consider that FICB affects the obturator nerve,and the suprainguinal FICB improves the incidence of successful obturator nerve block.