• Areti Adoni, Tilemachos Paraskeuopoulos, Theodosios Saranteas, Tatiana Sidiropoulou, Dimitrios Mastrokalos, and Georgia Kostopanagiotou.
• Department of Anesthesia and Cardiovascular Critical Care, University of Athens, Attikon University Hospital of Athens, Athens, Greece.
• J Anaesthesiol Clin Pharmacol. 2014 Jul 1;30(3):378-82.

Background And AimsThe anatomic site and the volume of local anesthetic needed for an ultrasound-guided saphenous nerve block differ in the literature. The purpose of this study was to examine the effect of two different ultrasound-guided low volume injections of local anesthetic on saphenous and vastus medialis nerves.Materials And MethodsRecruited patients (N = 48) scheduled for orthopedic surgery were randomized in two groups; Group distal adductor canal (DAC): Ultrasound-guided injection (5 ml of local anesthetic) distal to the inferior foramina of the adductor canal. Group adductor canal (AC): Ultrasound-guided injection (5 ml local anesthetic) within the adductor canal. Following the injection of local anesthetic, block progression was monitored in 5 min intervals for 15 min in the sartorial branches of the saphenous nerve and vastus medialis nerve.ResultsTwenty two patients in each group completed the study. Complete block of the saphenous nerve was observed in 55% and 59% in Group AC and DAC, respectively (P = 0.88). The proportion of patients with vastus medialis weakness at 15 min in Group AC, 36%, was significantly higher than in Group DAC (0/22), (P = 0.021).ConclusionsLow volume of local anesthetic injected within the adductor canal or distally its inferior foramina leads to moderate success rate of the saphenous nerve block, while only the injection within the adductor canal may result in vastus medialis nerve motor block.

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