Supra-inguinal Fascia Iliaca Block and the Obturator Nerve Obsession

Abstract

To the Editor, Anatomic block efficacy of lumbar plexus elements is based upon the involvement of the obturator nerve. However, despite the anatomic location of the obturator nerve and improbable translocation of local anesthetic beyond the confinement of the fascia iliacus plane [1], investigators struggle to study extensively, exhaustively, and try to explicitly describe the means and mechanism to block the obturator nerve [2]. Our anatomical dissections reveal three important dissimilar fascial planes (figure 1a). The quadratus lumborum, the fascia iliaca, and the circum-psoas planes are isolated from each other with tight fascial attachments [Figure 1b], impeding the dissemination of local anaesthetic agents unless inadvertently perforating the fascia. Further exploration revealed the femoral, lateral femoral cutaneous, obturator nerves and the lumbosacral trunk emerge from the lateral and medial of the psoas muscle respectively, and exits the psoas fascia (figure 1a,1b, and 1c) to take their respective course. The obturator nerve might further arise in a separate muscular fold (Figure 1c). However, if the obturator nerve needs to be blocked, two we recommend two alternatives; We presume that with injections deep to the psoas sheath, the plausibility of involvement of all the nerves of the lumbar plexus (lateral femoral cutaneous nerve, femoral nerve, and ON) exists, as reported in a case series [3] and the obturator nerve needs to be blocked separately after a supra-inguinal fascia iliaca block.