An Iliopsoas Plane Block does not Cause Motor Blockade: a Blinded Randomized Volunteer Trial

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BACKGROUND: A femoral nerve block relieves pain after total hip arthroplasty, but its use is controversial due to motor paralysis accompanied by an increased risk of fall. Assumedly, the iliopsoas plane block targets the hip articular branches of the femoral nerve without motor blockade. However, this has only been indicated by a cadaver study. Therefore, we designed the present volunteer study.

METHODS: Twenty healthy volunteers were randomly allocated to blinded paired active vs. sham iliopsoas plane block (5 mL lidocaine 18 mg/mL with epinephrine vs. saline). The primary outcome was reduction of maximal force of knee extension after iliopsoas plane block compared to baseline. Secondary outcomes included reduction of maximal force of hip adduction, and the pattern of injectate spread assessed with magnetic resonance imaging.

RESULTS: Mean (confidence interval) change of maximal force of knee extension from baseline to after iliopsoas plane block was -9.7 N (-22, 3.0) (p = 0.12) (n = 14). The injectate was consistently observed in an anatomically well-defined closed fascial compartment between the intra- and extrapelvic components of the iliopsoas muscle anterior to the hip joint.

CONCLUSION: We observed no significant reduction of maximal force of knee extension after an iliopsoas plane block. The injectate was contained in a fascial compartment previously shown to contain all sensory branches from the femoral nerve to the hip joint. The clinical consequence of selective anaesthesia of all sensory femoral nerve branches from the hip could be a reduced risk of fall compared to a traditional femoral nerve block.

Original languageEnglish
JournalActa Anaesthesiologica Scandinavica
Pages (from-to)368-377
Number of pages10
Publication statusPublished - 2020

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