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Femoral nerve “sheath” for inguinal paravascular lumbar plexus block is not found in human cadavers
Femoral Nerve “Sheath” for Inguinal Paravascular Lu-mbar Plexus Block Is Not Found in Human Cadavers John W. Ritter,
MD*
Anesthesiology Service, VA Medical Center West Los Angeles, Los Angeles, CA and Departments of Anesthesiology and Pathology, University of Vienna, Vienna, Austria.
*Associate Clinical Professor of Anesthesiology, V.A. Medical Center, West Los Angeles, CA, and UCLA School of Medicine, Los Angeles, CA Address reprint requests to Dr. Ritter at 8687 Falmouth Ave., # 105, Playa de1 Rey, CA 90293, USA. Supported by Medical Research Funds of the Department of Veterans Affairs Medical Center, West Los Angeles, CA. Presented in part at the Annual Meeting of the American Society of Anesthesiologists, Washington, D.C., October 9-13, 1993. Received for publication August 4, 1994; revised manuscript accepted for publication October 31, 1994.
Study Objective: To determine if a femoral nerve sheath capable of conveying local anesthetic to the lumbar plexus and the obturator nerve exists in human cadavers. Design: Injection of methylene blue dye into the femoral nerves of human cadavers followed by d‘assett’ton and observation of dye distribution. Setting: University medical center pathology department autopsy room. Patients: Six fresh adult cadavers about to undergo postmortem examination. Interventions: Both femoral nerves of six fresh cadavers were injected with either 20 ml or 40 ml of dye. The abdomen was opened and distribution of the dye was observed. Measurements and Main Results: In all of the cadavers studied there was no evidence of a femoral neroe sheath capable of conveying methylene blue dye to the lumbar plexus. Both 20 ml and 40 ml of dye injected into the femoral nerve failed to reach the lumbar plexus or the obturator nerve. When 40 ml of dye was injected it always stained the femoral nerves, it usually stained the lateral femoral cutaneous nerves, but it never stained the obturator nerves. Conclusions: A femoral nerue sheath capable of conveying a solution to the cadaver lumbar plexus doesnot exist in human cadavers. Dye injected into the cadaver femoral nerve does not reach either the lumbar plexus or the obturator nerve. When 40 ml of methylene blue dye is injected into the cadaver femoral nerve, some dye usually diffuses under the iliacus muscle fascia to the lateral femoral cutaneous nerve. This study indicates that in patients the “Y-in-1 block” always blocks the femoral nerve, it usually blocks the lateral femoral cutaneous nerve, but it probably does not block the lumbar plexus or the obturator nerve. Keywords: Anatomy: femoral nerve, lumbar plexus, nerve sheath; anesthesia, regional; anesthetic techniques: inguinal paravascular block, “3-in- 1 block”; cadaver.
Introduction The inguinal paravascular lumbar plexus block technique, “3-in- 1 block”, was described 2 1 years ago by Winnie et al. ’ These investigators hypothesized the existence of a fascial sheath around the femoral nerve forming a fluid conduit through which local anesthetic could be injected from below the inguinal ligament to the lumbar plexus, thus blocking the femoral, lateral femoral cutaneous, and obturator nerves with a single injection. The authors claimed that, “if a volume of 20 ml or more is utilized, anesthesia of all three nerves is virtually assured.“’
1995 Journal of Clinical Anesthesia 7:470473, 0 1995 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
0952~8180/95/$10.00 SSDI 0952-8180(95)00055-M
Femoral nerue sheath not found in cadavers: Ritter
Many experienced anesthesiologists cannot reproduce these results.2-5 It has been my experience that the 3-in-1 block always blocks the femoral nerve, usually blocks the lateral femoral cutaneous nerve, but never blocks the obturator nerve. This experience has been confirmed by a study of the various approaches to the lumbar plexus.2 This article reports a study designed to observe whether the femoral nerve has a fascial sheath capable of conveying methylene blue dye to the lumbar plexus and obturator nerve of the fresh adult cadaver.
Materials
and Methods
After obtaining proper consent and permission, six adult cadavers about to undergo postmortem examination were selected for this study. Cadavers with a history or evidence of surgery in the lower abdomen, pelvis, inguinal regions, or lower extremities were excluded. Those with evidence of recent invasive procedures or pathology of these anatomic regions were excluded. All cadavers were mature adults. Age, height, and weight were not criteria for selection. Careful bilateral dissection below both inguinal ligaments exposed the femoral nerves prior to division into their terminal branches. Dissection was performed without disturbing the adjacent anatomic structures. A 5 cm, 20-gauge catheter was inserted into the center of each femoral nerve and secured with two silk sutures. Methylene blue dye 20 ml was slowly injected under low pressure into one catheter and 40 ml into the contralateral catheter. The abdominal cavity was then opened and the location of the dye observed. The iliacus muscle fascia was then opened and the lateral femoral cutaneous, femoral, and obturator nerves were dissected free. The extent to which these nerves were stained with dye was ascertained. The lumbar plexus was then dissected out of the psoas muscle. Sections of the femoral nerve were taken for subsequent histologic examination.
Results In none of the cadavers did the dye flow along the femoral nerve as though surrounded by a fascial sheath. Instead, most of the dye spread laterally over the iliopsoas and iliacus muscles below the iliacus muscle fascia. Because the iliacus fascia was attached to the pelvic rim, the dye did not spread medially into the pelvis. In some cadavers, dye tracked cephalad in the groove formed by the psoas major and iliacus muscles, but it did not follow the femoral nerve into the psoas major muscle and lumbar plexus. Regardless of the volume of dye injected, it never reached the lumbar plexus or the obturator nerve. In five of six cadavers, when 40 ml of dye was injected, the femoral and lateral femoral cutaneous nerves were stained with dye. The obturator nerve was not (F@~re 1). Along the course of the femoral nerve there was no indication that dye was contained within the nerve by an
anatomic structure. It diffused through the femoral nerve epineurium without apparent restraint. No dye was found within the fascia of the psoas major muscle where the lumbar plexus was located. The genitofemoral nerve, which is derived from the lumbar plexus and shares the second lumbar (L2) spinal nerve fibers with the lateral femoral cutaneous and obturator nerves, was not stained. It was observed that the femoral nerve lay on top of the iliopsoas and iliacus muscles, covered only by the muscle fascia. Methylene blue dye did not penetrate through the fascia into the abdominal cavity. Review of the femoral nerve histology preparations failed to reveal a nonfenestrated connective tissue sheath on any of the slides. There was no gross or microscopic anatomic evidence of a femoral nerve fascial sheath.
Discussion Many anesthesiologists use spinal or epidural blocks for surgical anesthesia of the leg. Although these two regional techniques usually provide rapid, complete, and safe anesthesia, they also may cause significant sympathetic block.&’ Anesthesia of the leg below the tibia1 tuberosity can be achieved with two injections, one for the sciatic and posterior femoral nerves, and one for the femoral nerve. ‘OS1 ’ However, leg surgery above the tibia1 tuberosity requires neural blockade of five nerves: sciatic, posterior femoral cutaneous (which is blocked with the sciatic), lateral femoral cutaneous, femoral, and obturator.“,” The latter three nerves are derived from the lumbar plexus. 12-14 If the lumbar plexus could be blocked with a single injection, then only two injections would be sufficient to anesthetize the entire lower extremity. In an attempt to block the lumbar plexus with a single injection, the inguinal paravascular lumbar plexus block (3-in-1 block) technique was proposed by Winnie et al.’ These researchers hypothesized the existence of a fascial sheath around the femoral nerve, forming a fluid conduit through which local anesthetic could pass from below the inguinal ligament to the lumbar plexus. They claimed that a 20 ml volume of local anesthetic injected into the femoral nerve sheath blocked the femoral, lateral femoral cutaneous, and obturator nerves.’ The study of Winnie et al.’ evaluated the neural blockade of patients “about to undergo leg operations.” No mention was made as to whether the surgeries in their study were above or below the tibia1 tuberosity. The criterion for determining blockade of the three peripheral nerves was never elucidated. Experienced anesthesiologists have tried to use the inguinal aravascular lumbar plexus block for upper leg surgery. 9 Unfortunately, they have not been able to reproduce the results of Winnie et al.’ The lumbar plexus is created from the ventral rami of spinal nerves L,, L,, Ls, half of L,, and frequently a J. Clin. Anesth., vol. 7, September
1995
471
Original Contribution
Figu tre 1. Laying folla Iwing femoral
across the forceps, the femoral (middle) and lateral femoral cutaneous (right) nerves are dyed blue intraneural injection of 40 ml methylene blue dye. The obturator nerve (left) is not dyed.
communicating branch of the twelfth thoracic (T 1.2).‘z-l4 It is formed within the dorsal muscle fibers of the psoas major muscle, ventral to the vertebral transverse processes of the lumbar vertebrae.“-l4 The six peripheral nerves of the lumbar plexus are: iliohypogastric L,, ilioinguinal L,, genitofemoral Lr-L,, lateral femoral cutaneous L,-L,, obturator L,-L,, and femoral L,--L,. The lateral femoral cutaneous nerve exits the psoas major muscle on the dorsal lateral side and runs obliquely across the iliacus muscle to the anterior superior iliac spine beneath the muscle fascia. The genitofemoral nerve exits the psoas muscle on the ventral side of psoas major muscle. The genital branch enters the inguinal canal to supply the scrotum or labium majus. The femoral branch enters the femoral sheath with the femoral artery and vein and supplies the skin of the femoral triangle. The femoral nerve exits the psoas major muscle on the dorsal medial side. It then passes caudad in a groove between the psoas major and iliacus muscles covered by the iliacus fascia. The psoas major and iliacus muscles combine to form the iliopsoas muscle. The femoral nerve continues toward the leg on the ventral sidle of the ilio soas muscle covered only by the iliacus muscle fascia. P*,13 The femoral nerve and iliopsoas muscle pass under the inguinal ligament in the lacuna musculorum. 472
J. Clin. Anesth., vol. 7, September 1995
The femoral artery and vein are contained within the femoral sheath, which passes under the inguinal ligament in the lacuna vasorum and are separated from the femoral nerve by the thick iliopectineal ligament. The femoral nerve, artery, and vein are not contained in a common neurovascular bundle.’ l-l3 The obturator nerve exits the psoas muscle on the medial side at the inlet of the pelvis. It descends into the pelvis dorsal to the common iliac vessels, exiting the pelvis through the obturator foramen. It bifurcates into anterior and posterior branches. Terminal branches of the obturator nerve anastomose with the saphenous nerve, the terminal sensory branch of femoral nerve, forming the subsartorial plexus; branches from it supply the overlying skin. Although the obturator nerve is primarily a motor nerve, the anterior branch does have a sensory distribution to the hip joint, the femur, and occasionally the knee joint. There is a small variable area of cutaneous innervation located on the medial aspect of the thigh overlapped by cutaneous branches of the femoral and sciatic nerves. This cutaneous innervation is sometimes missing.13’14 The lateral femoral cutaneous nerve, the obturator nerve, and the genitofemoral nerve all derive a significant number of lumbar spinal nerve fibers from L,. If the inguinal paravascular 3-in-1 block anesthetized the
Femoral nerve sheath not found in cadavers: Ritter
femoral cutaneous nerve via the lumbar plexus, the genitofemoral nerve should occasionally be blocked. I have not found such clinical reports. The anatomy literature fails to describe a fascial “sheath” around the femoral nerve capable of acting as a liquid conduit to the lumbar plexus.‘2-‘5 Although there are reports that the inguinal paravascular block technique does not anesthetize the obturator nerve, 225this study does not prove that under clinical conditions the obturator nerve is never blocked. Conclusions This cadaver study demonstrates that the femoral nerve does not have a fascial “sheath” capable of conveying a liquid from below the inguinal ligament to the lumbar plexus. In patients, the 3-in-1 block is probably a femoral nerve block that diffuses laterally under the iliacus fascia to the lateral femoral cutaneous nerve when a large enough volume of local anesthetic is injected. It probably does not block the obturator nerve. The 3-in-1 block technique, with 40 ml of local anesthetic, should always block the femoral nerve, it should usually block the lateral femoral cutaneous nerve, but it should not be expected to block the lumbar plexus or the obturator nerve.
Acknowledgments I wish to thank Professor M. Zimpfer, Chairman, Department of Anesthesiology, University of Vienna, and Professor J. Holzner, Chairman, Department of Pathology, University of Vienna, Austria, for their kind hospitality and assistance with this study.
References 1. Winnie AP, Ramamurthy S, Durrani 2: The inguinal paravascular technic of lumbar plexus anesthesia: the “3-in-l block.” An&h Analg 1973;52:989-96.
2. Parkinson SK, Mueller JB, Little WL, Bailey SL: Extent of blockade with various approaches to the lumbar plexus. Anesth Analg 1989;68:243-8. 3. Madej TH, Ellis FR, Halsall PJ: Evaluation of “3 in 1” lumbar plexus block in patients having muscle biopsy. Br J Anaesth 1989;62:515-7. 4 Spillane WF: 3-in-1 blocks and continuous ter]. RegAnesth 1992;17:1’75-6.
3-in-1 blocks [Let-
5. Lang SA, Yip RW, Chang PC, Gerard MA: The femoral block revisited. J Clin Anesth 1993;5:292-6.
3-in-1
6. Bridenbaugh P: The lower extremity: somatic blockade. In: Cousins M, Bridenbaugh P (eds): Neural Blockade in Clinical Anesthesia and Management of Pain, 2d ed. Philadelphia: J.B. Lippincott Co., 1988:41740. 7. Cousins M, Bromage P: Epidural neural blockade. In: Cousins M, Bridenbaugh P (eds): Neural Blockade in Clinical Anesthesia and Management of Pain, 2d ed. Philadelphia: J.B. Lippincott Co., 1988:253-346. 8. Brown D: Spinal, epidural, and caudal anesthesia. In: Miller R (ed): Anesthesia, 4th ed. New York: Churchill Livingstone, 1994: 1505-30. 9. Covino BG, Lambert D: Epidural and spinal anesthesia. In: Barash PG, Cullen BF, Stoelting RK (eds): Clinical Anesthesia, 2d ed. Philadelphia: J.B. Lippincott Co., 1992:809-38. 10. Moore D: Regional Block, 9th ed. Springfield, Thomas, Publishers, 1971:286-8.
IL: Charles
C.
11. Wedel D: Nerve blocks. In: Miller R (ed): Anesthesia, 4th ed. New York, N.Y: Churchill Livingstone, 1994:1535-63. 12. Pernkopf E: Topical Human Anatomy. Vienna, Austria: ban und Schwarzenberg, Publisher, 1941, 2:183-184.
Ur-
13. Spalterholz W: Hand Atlas of Human Anatomy, 13th ed. Philadelphia: J.B. Lippincott Co., 1950:3434. 14. Gardner E, Bunge R: Gross anatomy of the peripheral nervous system. In: Dyck P, Thomas P (eds): Peripheral New-apathy, 3rd ed. Philadelphia: W.B. Saunders Co., 1993:21-2. 15. Thomas P, Berthold C, Ochoa J: Microscopic anatomy of the peripheral nervous system. In: Dyck P, Thomas P (eds): Peripheral Neuropathy, 3rd ed. Philadelphia: W.B. Saunders Co., 1993:21.
J. Clin. Anesth., vol. 7, September
1995
473
MD*
Anesthesiology Service, VA Medical Center West Los Angeles, Los Angeles, CA and Departments of Anesthesiology and Pathology, University of Vienna, Vienna, Austria.
*Associate Clinical Professor of Anesthesiology, V.A. Medical Center, West Los Angeles, CA, and UCLA School of Medicine, Los Angeles, CA Address reprint requests to Dr. Ritter at 8687 Falmouth Ave., # 105, Playa de1 Rey, CA 90293, USA. Supported by Medical Research Funds of the Department of Veterans Affairs Medical Center, West Los Angeles, CA. Presented in part at the Annual Meeting of the American Society of Anesthesiologists, Washington, D.C., October 9-13, 1993. Received for publication August 4, 1994; revised manuscript accepted for publication October 31, 1994.
Study Objective: To determine if a femoral nerve sheath capable of conveying local anesthetic to the lumbar plexus and the obturator nerve exists in human cadavers. Design: Injection of methylene blue dye into the femoral nerves of human cadavers followed by d‘assett’ton and observation of dye distribution. Setting: University medical center pathology department autopsy room. Patients: Six fresh adult cadavers about to undergo postmortem examination. Interventions: Both femoral nerves of six fresh cadavers were injected with either 20 ml or 40 ml of dye. The abdomen was opened and distribution of the dye was observed. Measurements and Main Results: In all of the cadavers studied there was no evidence of a femoral neroe sheath capable of conveying methylene blue dye to the lumbar plexus. Both 20 ml and 40 ml of dye injected into the femoral nerve failed to reach the lumbar plexus or the obturator nerve. When 40 ml of dye was injected it always stained the femoral nerves, it usually stained the lateral femoral cutaneous nerves, but it never stained the obturator nerves. Conclusions: A femoral nerue sheath capable of conveying a solution to the cadaver lumbar plexus doesnot exist in human cadavers. Dye injected into the cadaver femoral nerve does not reach either the lumbar plexus or the obturator nerve. When 40 ml of methylene blue dye is injected into the cadaver femoral nerve, some dye usually diffuses under the iliacus muscle fascia to the lateral femoral cutaneous nerve. This study indicates that in patients the “Y-in-1 block” always blocks the femoral nerve, it usually blocks the lateral femoral cutaneous nerve, but it probably does not block the lumbar plexus or the obturator nerve. Keywords: Anatomy: femoral nerve, lumbar plexus, nerve sheath; anesthesia, regional; anesthetic techniques: inguinal paravascular block, “3-in- 1 block”; cadaver.
Introduction The inguinal paravascular lumbar plexus block technique, “3-in- 1 block”, was described 2 1 years ago by Winnie et al. ’ These investigators hypothesized the existence of a fascial sheath around the femoral nerve forming a fluid conduit through which local anesthetic could be injected from below the inguinal ligament to the lumbar plexus, thus blocking the femoral, lateral femoral cutaneous, and obturator nerves with a single injection. The authors claimed that, “if a volume of 20 ml or more is utilized, anesthesia of all three nerves is virtually assured.“’
1995 Journal of Clinical Anesthesia 7:470473, 0 1995 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
0952~8180/95/$10.00 SSDI 0952-8180(95)00055-M
Femoral nerue sheath not found in cadavers: Ritter
Many experienced anesthesiologists cannot reproduce these results.2-5 It has been my experience that the 3-in-1 block always blocks the femoral nerve, usually blocks the lateral femoral cutaneous nerve, but never blocks the obturator nerve. This experience has been confirmed by a study of the various approaches to the lumbar plexus.2 This article reports a study designed to observe whether the femoral nerve has a fascial sheath capable of conveying methylene blue dye to the lumbar plexus and obturator nerve of the fresh adult cadaver.
Materials
and Methods
After obtaining proper consent and permission, six adult cadavers about to undergo postmortem examination were selected for this study. Cadavers with a history or evidence of surgery in the lower abdomen, pelvis, inguinal regions, or lower extremities were excluded. Those with evidence of recent invasive procedures or pathology of these anatomic regions were excluded. All cadavers were mature adults. Age, height, and weight were not criteria for selection. Careful bilateral dissection below both inguinal ligaments exposed the femoral nerves prior to division into their terminal branches. Dissection was performed without disturbing the adjacent anatomic structures. A 5 cm, 20-gauge catheter was inserted into the center of each femoral nerve and secured with two silk sutures. Methylene blue dye 20 ml was slowly injected under low pressure into one catheter and 40 ml into the contralateral catheter. The abdominal cavity was then opened and the location of the dye observed. The iliacus muscle fascia was then opened and the lateral femoral cutaneous, femoral, and obturator nerves were dissected free. The extent to which these nerves were stained with dye was ascertained. The lumbar plexus was then dissected out of the psoas muscle. Sections of the femoral nerve were taken for subsequent histologic examination.
Results In none of the cadavers did the dye flow along the femoral nerve as though surrounded by a fascial sheath. Instead, most of the dye spread laterally over the iliopsoas and iliacus muscles below the iliacus muscle fascia. Because the iliacus fascia was attached to the pelvic rim, the dye did not spread medially into the pelvis. In some cadavers, dye tracked cephalad in the groove formed by the psoas major and iliacus muscles, but it did not follow the femoral nerve into the psoas major muscle and lumbar plexus. Regardless of the volume of dye injected, it never reached the lumbar plexus or the obturator nerve. In five of six cadavers, when 40 ml of dye was injected, the femoral and lateral femoral cutaneous nerves were stained with dye. The obturator nerve was not (F@~re 1). Along the course of the femoral nerve there was no indication that dye was contained within the nerve by an
anatomic structure. It diffused through the femoral nerve epineurium without apparent restraint. No dye was found within the fascia of the psoas major muscle where the lumbar plexus was located. The genitofemoral nerve, which is derived from the lumbar plexus and shares the second lumbar (L2) spinal nerve fibers with the lateral femoral cutaneous and obturator nerves, was not stained. It was observed that the femoral nerve lay on top of the iliopsoas and iliacus muscles, covered only by the muscle fascia. Methylene blue dye did not penetrate through the fascia into the abdominal cavity. Review of the femoral nerve histology preparations failed to reveal a nonfenestrated connective tissue sheath on any of the slides. There was no gross or microscopic anatomic evidence of a femoral nerve fascial sheath.
Discussion Many anesthesiologists use spinal or epidural blocks for surgical anesthesia of the leg. Although these two regional techniques usually provide rapid, complete, and safe anesthesia, they also may cause significant sympathetic block.&’ Anesthesia of the leg below the tibia1 tuberosity can be achieved with two injections, one for the sciatic and posterior femoral nerves, and one for the femoral nerve. ‘OS1 ’ However, leg surgery above the tibia1 tuberosity requires neural blockade of five nerves: sciatic, posterior femoral cutaneous (which is blocked with the sciatic), lateral femoral cutaneous, femoral, and obturator.“,” The latter three nerves are derived from the lumbar plexus. 12-14 If the lumbar plexus could be blocked with a single injection, then only two injections would be sufficient to anesthetize the entire lower extremity. In an attempt to block the lumbar plexus with a single injection, the inguinal paravascular lumbar plexus block (3-in-1 block) technique was proposed by Winnie et al.’ These researchers hypothesized the existence of a fascial sheath around the femoral nerve, forming a fluid conduit through which local anesthetic could pass from below the inguinal ligament to the lumbar plexus. They claimed that a 20 ml volume of local anesthetic injected into the femoral nerve sheath blocked the femoral, lateral femoral cutaneous, and obturator nerves.’ The study of Winnie et al.’ evaluated the neural blockade of patients “about to undergo leg operations.” No mention was made as to whether the surgeries in their study were above or below the tibia1 tuberosity. The criterion for determining blockade of the three peripheral nerves was never elucidated. Experienced anesthesiologists have tried to use the inguinal aravascular lumbar plexus block for upper leg surgery. 9 Unfortunately, they have not been able to reproduce the results of Winnie et al.’ The lumbar plexus is created from the ventral rami of spinal nerves L,, L,, Ls, half of L,, and frequently a J. Clin. Anesth., vol. 7, September
1995
471
Original Contribution
Figu tre 1. Laying folla Iwing femoral
across the forceps, the femoral (middle) and lateral femoral cutaneous (right) nerves are dyed blue intraneural injection of 40 ml methylene blue dye. The obturator nerve (left) is not dyed.
communicating branch of the twelfth thoracic (T 1.2).‘z-l4 It is formed within the dorsal muscle fibers of the psoas major muscle, ventral to the vertebral transverse processes of the lumbar vertebrae.“-l4 The six peripheral nerves of the lumbar plexus are: iliohypogastric L,, ilioinguinal L,, genitofemoral Lr-L,, lateral femoral cutaneous L,-L,, obturator L,-L,, and femoral L,--L,. The lateral femoral cutaneous nerve exits the psoas major muscle on the dorsal lateral side and runs obliquely across the iliacus muscle to the anterior superior iliac spine beneath the muscle fascia. The genitofemoral nerve exits the psoas muscle on the ventral side of psoas major muscle. The genital branch enters the inguinal canal to supply the scrotum or labium majus. The femoral branch enters the femoral sheath with the femoral artery and vein and supplies the skin of the femoral triangle. The femoral nerve exits the psoas major muscle on the dorsal medial side. It then passes caudad in a groove between the psoas major and iliacus muscles covered by the iliacus fascia. The psoas major and iliacus muscles combine to form the iliopsoas muscle. The femoral nerve continues toward the leg on the ventral sidle of the ilio soas muscle covered only by the iliacus muscle fascia. P*,13 The femoral nerve and iliopsoas muscle pass under the inguinal ligament in the lacuna musculorum. 472
J. Clin. Anesth., vol. 7, September 1995
The femoral artery and vein are contained within the femoral sheath, which passes under the inguinal ligament in the lacuna vasorum and are separated from the femoral nerve by the thick iliopectineal ligament. The femoral nerve, artery, and vein are not contained in a common neurovascular bundle.’ l-l3 The obturator nerve exits the psoas muscle on the medial side at the inlet of the pelvis. It descends into the pelvis dorsal to the common iliac vessels, exiting the pelvis through the obturator foramen. It bifurcates into anterior and posterior branches. Terminal branches of the obturator nerve anastomose with the saphenous nerve, the terminal sensory branch of femoral nerve, forming the subsartorial plexus; branches from it supply the overlying skin. Although the obturator nerve is primarily a motor nerve, the anterior branch does have a sensory distribution to the hip joint, the femur, and occasionally the knee joint. There is a small variable area of cutaneous innervation located on the medial aspect of the thigh overlapped by cutaneous branches of the femoral and sciatic nerves. This cutaneous innervation is sometimes missing.13’14 The lateral femoral cutaneous nerve, the obturator nerve, and the genitofemoral nerve all derive a significant number of lumbar spinal nerve fibers from L,. If the inguinal paravascular 3-in-1 block anesthetized the
Femoral nerve sheath not found in cadavers: Ritter
femoral cutaneous nerve via the lumbar plexus, the genitofemoral nerve should occasionally be blocked. I have not found such clinical reports. The anatomy literature fails to describe a fascial “sheath” around the femoral nerve capable of acting as a liquid conduit to the lumbar plexus.‘2-‘5 Although there are reports that the inguinal paravascular block technique does not anesthetize the obturator nerve, 225this study does not prove that under clinical conditions the obturator nerve is never blocked. Conclusions This cadaver study demonstrates that the femoral nerve does not have a fascial “sheath” capable of conveying a liquid from below the inguinal ligament to the lumbar plexus. In patients, the 3-in-1 block is probably a femoral nerve block that diffuses laterally under the iliacus fascia to the lateral femoral cutaneous nerve when a large enough volume of local anesthetic is injected. It probably does not block the obturator nerve. The 3-in-1 block technique, with 40 ml of local anesthetic, should always block the femoral nerve, it should usually block the lateral femoral cutaneous nerve, but it should not be expected to block the lumbar plexus or the obturator nerve.
Acknowledgments I wish to thank Professor M. Zimpfer, Chairman, Department of Anesthesiology, University of Vienna, and Professor J. Holzner, Chairman, Department of Pathology, University of Vienna, Austria, for their kind hospitality and assistance with this study.
References 1. Winnie AP, Ramamurthy S, Durrani 2: The inguinal paravascular technic of lumbar plexus anesthesia: the “3-in-l block.” An&h Analg 1973;52:989-96.
2. Parkinson SK, Mueller JB, Little WL, Bailey SL: Extent of blockade with various approaches to the lumbar plexus. Anesth Analg 1989;68:243-8. 3. Madej TH, Ellis FR, Halsall PJ: Evaluation of “3 in 1” lumbar plexus block in patients having muscle biopsy. Br J Anaesth 1989;62:515-7. 4 Spillane WF: 3-in-1 blocks and continuous ter]. RegAnesth 1992;17:1’75-6.
3-in-1 blocks [Let-
5. Lang SA, Yip RW, Chang PC, Gerard MA: The femoral block revisited. J Clin Anesth 1993;5:292-6.
3-in-1
6. Bridenbaugh P: The lower extremity: somatic blockade. In: Cousins M, Bridenbaugh P (eds): Neural Blockade in Clinical Anesthesia and Management of Pain, 2d ed. Philadelphia: J.B. Lippincott Co., 1988:41740. 7. Cousins M, Bromage P: Epidural neural blockade. In: Cousins M, Bridenbaugh P (eds): Neural Blockade in Clinical Anesthesia and Management of Pain, 2d ed. Philadelphia: J.B. Lippincott Co., 1988:253-346. 8. Brown D: Spinal, epidural, and caudal anesthesia. In: Miller R (ed): Anesthesia, 4th ed. New York: Churchill Livingstone, 1994: 1505-30. 9. Covino BG, Lambert D: Epidural and spinal anesthesia. In: Barash PG, Cullen BF, Stoelting RK (eds): Clinical Anesthesia, 2d ed. Philadelphia: J.B. Lippincott Co., 1992:809-38. 10. Moore D: Regional Block, 9th ed. Springfield, Thomas, Publishers, 1971:286-8.
IL: Charles
C.
11. Wedel D: Nerve blocks. In: Miller R (ed): Anesthesia, 4th ed. New York, N.Y: Churchill Livingstone, 1994:1535-63. 12. Pernkopf E: Topical Human Anatomy. Vienna, Austria: ban und Schwarzenberg, Publisher, 1941, 2:183-184.
Ur-
13. Spalterholz W: Hand Atlas of Human Anatomy, 13th ed. Philadelphia: J.B. Lippincott Co., 1950:3434. 14. Gardner E, Bunge R: Gross anatomy of the peripheral nervous system. In: Dyck P, Thomas P (eds): Peripheral New-apathy, 3rd ed. Philadelphia: W.B. Saunders Co., 1993:21-2. 15. Thomas P, Berthold C, Ochoa J: Microscopic anatomy of the peripheral nervous system. In: Dyck P, Thomas P (eds): Peripheral Neuropathy, 3rd ed. Philadelphia: W.B. Saunders Co., 1993:21.
J. Clin. Anesth., vol. 7, September
1995
473