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Femoral Nerve Block

  • Indications include hip, femur, patella, quadriceps tendon, and knee surgery.
  • Femoral nerve is the largest branch of the lumbar plexus (L2-L4).
  • Primary motor innervation of the main hip flexors and knee extensors.
  • Primary sensory innervation of the hip and thigh.
  • The saphenous branch extends sensory innervation to the medial leg and ankle joint.
  • Complications include infection, hematoma, vascular puncture, nerve injury.
  • Nerve Stimulation Technique: While patient is supine, palpate the femoral artery at the level of the inguinal crease just below the inguinal ligament. Insert needle at 45 angle, in a cephalad direction, approximately 1cm lateral to the femoral pulse. Observe for distinct quadriceps twitch or patella motion that is elicited with a current <0.5 mA.
  • Ultrasound Guided Technique: While patient is supine, place the transducer transversely on the inguinal crease. Move from lateral to medial until the femoral nerve, artery, and vein are identified. Insert the needle in-plane with the transducer in a lateral to medial orientation. Circumferential spread of local anesthetic is not necessary.
  • Tips:
    • A “pop” may be felt as the needle is advanced through the fascia lata and iliaca. The needle tip must be below this structure to obtain a complete block.
    • Sartorius muscle twitches are common and occur when the needle encounters one of the anterior femoral nerve branches. Sartorius twitches may be elicited if the needle tip is too anterior and/or medial to the main trunk of femoral nerve. Try redirecting the needle deeper and more lateral to obtain patella twitch, which assures the needle tip is in the vicinity of the main trunk of the femoral nerve. .
    • Tilting the transducer either cranially or caudally can help identify the femoral nerve. While applying pressure may help optimize the image of the nerve, be cautious of collapsing veins and obscuring them from view.
    • Volumes larger than 15-20mL have not been associated with higher success rates.

Other References

  1. Madison, Sarah J., and Brian M. Ilfeld. "Peripheral Nerve Blocks." Morgan & Mikhail's Clinical Anesthesiology, 6e Eds. John F. Butterworth IV, et al. New York, NY: McGraw-Hill Link
  2. “Femoral Nerve Block - Landmarks and Nerve Stimulator Technique.” NYSORA, 18 Sept. 2019 Link
  3. “Ultrasound-Guided Femoral Nerve Block.” NYSORA, 23 May 2019 Link