Chapter 38. Lumbar Paravertebral Sonography and Considerations for Ultrasound-Guided Lumbar Plexus Block
Mark the correct statement regarding the lumbar plexus (LP).
A. The LP is formed by contribution from dorsal primary rami of L1–L4.
B. The LP lies within the anterior one-third of psoas muscle.
C. Nerves originating from the LP follow a relatively consistent pattern with the lateral femoral cutaneous nerve being innermost.
D. Psoas muscle contains lumbar nerve roots and branches of the lumbar artery.
D is correct. Psoas muscle does contain lumbar nerve roots and branches of the lumbar artery.
A is incorrect. The LP is formed by ventral (or anterior) primary rami of L1–L4 (not dorsal rami).
B is incorrect. The LP lies within the posterior one-third of psoas.
C is incorrect. The nerves that originate from the LP exhibit a somewhat consistent distribution, with the lateral femoral cutaneous nerve being outermost, the obturator nerve innermost, and the femoral nerve in between. The positions of the lateral femoral cutaneous nerve and femoral within the psoas compartment are relatively consistent, but the location of the obturator nerve is variable.
Lumbar plexus block (LPB) is best suited to provide analgesia following which of the following surgical procedures?
A. Achilles tendon repair
C. Hallux valgus correction
D. Total hip arthroplasty
D is correct. The hip joint is supplied by the femoral and obturator nerves that arise from the lumbar plexus. Other nerves that supply the hip joint such as sciatic, and superior gluteal nerves, as well as the nerve to the quadratus femoris arise from sacral plexus.
A, B, and C are incorrect. Hip and knee joints get a significant innervation from branches of the lumbar plexus. On the contrary, the foot and ankle are mainly supplied by the sciatic nerve with a minor contribution by saphenous nerve.
During performance of ultrasound (US)-guided lumbar plexus block (LPB):
A. Basic skill is required for interpretation of sonogram and needling.
B. A trident sonogram can be visualized in transverse scan.
C. A shamrock sonogram can be visualized in parasagittal scan.
D. Dual guidance using ultrasound and nerve stimulation is recommended while performing the block.