Does obturator nerve block always occur in 3-1 block ? Obturator sinir 3-1 blok ile her zaman bloke olur mu ?

J Clin Exp Invest www.clinexpinvest.org Vol 2, No 2, June 2011 Yazışma Adresi /Correspondence: Doç. Dr. Pakize Kırdemir, Medical Faculty of Suleyman Demirel University, Department of Anesthesia and Reanimation, Isparta-Turkey, Email: pkirdemir@hotmail.com Geliş Tarihi / Received: 29.07.2010, Kabul Tarihi / Accepted: 09.04.2011 Copyright © Klinik ve Deneysel Araştırmalar Dergisi 2011, Her hakkı saklıdır / All rights reserved Klinik ve Deneysel Araştırmalar Dergisi / 2011; 2 (2): 149-151 Journal of Clinical and Experimental Investigations


INTRODUCTION
Block 3 in 1 was described by Winnie in 1973. 1 This technique is supposed to block of the femoral, femoral cutaneous, and obturator nerves by a single injection.In recent years, this technique has been used as an effective alternative for arthroscopic surgery anesthesia and any superficial surgery such as skin harvesting or a biopsy of the quadriceps muscle can be done.Winnie, hypothesized that "If a volume of 20 ml or more is utilized, anesthesia of all three nerves is virtually assured". 1Ritter indicates that "3-in-1 block" probably does not block the lumbar plexus or the obturator nerve. 2 Lonsdale 3 has confirmed Winnie's anatomical hypothesis. 3turator nerve block is routinely unsuccessful in the femoral "3-in-1 block".Anatomical studies are not available to explain why blockade of obturator nerve or lumbar plexus does not occur.Therefore, in this study, we performed an anatomical cadaveric study to explain the anatomical basis of why obturator nerve block does not occur.

MATERIALS AND METHODS
Totally, 12 mature adult human cadavers were selected for the study.Cadavers with a history or evidence of surgery in the lower abdomen, pelvis and inguinal regions were excluded.Age, height, and weight were not included as the criteria for selection in all of the cadavers.A 15 cm, 22-gauge catheter was inserted 2 cm distal to the inguinal ligament and 1cm lateral to the femoral artery at a 30º angle cephalad and underneath the iliac fascia and fascia lata.Thirty ml of methylene blue dye was slowly injected via the catheter.Without disturbing the adjacent anatomic structures bilateral dissection was performed.
The fascia of the iliacus muscle was opened and the femoral, lateral femoral cutaneus and obturator nerves were dissected.Sections in horizontal planes were made and examined in Department of Anatomy with an aid of surgical microscope.In four cadavers, inguinal section of the femoral nerve was dissected and a catheter was inserted at a 5° angle and 1 cm thrust into the sheath and 30 ml of dye was injected.The abdominal cavity was then opened and we observed if the nerves were stained with dye.

RESULTS
In eight cadavers where the dye was injected laterally into the femoral sheath, the dye did not spread to the medial part of the psoas major muscle and the obturator nerve was not stained with the dye.Two other nerves were stained with dye in all cadavers.In four cadavers, a part of the femoral sheath under the inguinal ligament was found to be very thick and after careful dissection of this region, it was ob-served to be comprised of the part above the inguinal ligament blending with the iliac and psoas fascia.The sections in horizontal plane, examined with microscopic dissection, support these findings.
Based on our observations, this sheath cannot transport the local anesthetic to the lumbar plexus because this sheath covering the femoral nerve is not thick or strong enough and has a cribriform structure.Cadavers in whom dye was injected in the femoral sheath, the lateral femoral cutaneous nerve and the femoral nerve were stained with dye; during the dissection, we observed that the part under the psaos was not stained with the dye because the mass of the psoas muscle was pressured where the cross section of this nerve was seen to be flat and somewhat wide.Dye was spread through the fascial layers in the plane under the psoas muscle and the obturator nerve was found to be stained with dye just before emerging medially from the fascia psoas and at that point, the obturator nerve pierced the psoas fascia and extended extrafascially in the medial and deep border of the psoas muscle and the upper section of the obturator nerve was also seen to be stained with dye.

DISCUSSION
Major potential benefits of peripheral nerve block techniques may include postoperative analgesia, less physiologic derangements, more rapid postoperative recovery, avoidance of airway instrumentation, and a reduced incidence of potential complications associated with general anesthesia (nausea/ vomiting, aspiration, inability to ventilate/intubate, and malignant hyperthermia).Cauhepe et al. 4 have reported that the external diffusion of the liquid in front of the iliacus muscle never reached the internal side of the psoas major muscle, and thus the obturator nerve, in their anatomical study. 46][7][8] In a study, femoral and lateral femoral cutaneous nerves have been stained following femoral intraneural injection, but the obturator nerve has not been stained.Our findings support that the femoral nerve does not have a fascial sheath but following our injection, dye was spread posteriorly and cephalad to a point above where the obturator nerve pierces the illiacus fascia.It has been stated that, this technique anesthe- sizes only two nerves, and hence should be called a "2-in-1 block" and others reported that lateral femoral cutaneous nerve is blocked almost every time, but only four patients had abductor paralysis following the 3-in-1 block. 9,10Rosenblatt's report presented X-ray evidence that a catheter can be placed in the sheath surrounding the femoral nerve. 11Our findings support that liquid cannot spread medially to reach the obturator nerve because this nerve is extrafascial on the medial side of the psoas.Having the anesthetic reach the obturator nerve is possible because of the relation of the femoral nerve sheath with the fascial structure of this region.
For obturator nerve blockade, the anesthetic should be injected in the femoral nerve sheath and we believe that our method would increase the success of this nerve block.In a study, it has been concluded that the femoral 3-in-1 block does not block the parent trunk of the obturator nerve, where the obturator nerve block was successful in only one of 26 patients. 12Dupré indicates that "3-in-1" block is supported by the idea of diffusion within a space that is located after going through two fascial layers. 13However, when we used this space in eight cadavers, we spared the obturator nerve completely because of the anatomic structure of the psoas muscle cleavage and extrafascial obturator nerve.
As a conclusion, cause of an unsuccessful obturator nerve block may not be related to the experience of anesthesiologist but it may be depends on the fascial anatomy of this region.The femoral nerve is covered with a "sheath" which is thicker around the inguinal ligament.The lateral cutaneous femoral nerve and the femoral nerve are subfascial and these two nerves easily can be blocked in the fascia iliaca compartment, but the obturator nerve block fails because of its being extrafascial in this region.