Chapter 141. Psoas Compartment (Posterior Lumbar Plexus) Block

Anatomy:

• The lumbar plexus originates from L1 to L4, with often a contribution from T12. L4 gives off a branch that merges with L5 to form the lumbosacral branch, part of the sacral plexus
• Branches of the lumbar plexus include:
  • Femoral nerve
  • Lateral femoral cutaneous nerve
  • Obturator nerve
  • Ilioinguinal, iliohypogastric, and genitofemoral nerves
• The lumbar plexus courses through the lumbar area and the pelvis in the sheath of the psoas, and then the iliopsoas muscle (Figure 141-2)

Indications:

• Postoperative analgesia of hip or knee surgery (associated or not to a sacral plexus block); probably no advantage over femoral nerve block for knee surgery:
  • Hip arthroscopy
  • Proximal femur ORIF
  • Hip hemiarthroplasty/THA
• Anesthesia for lower extremity surgery, in association with a sacral plexus block
• The block of the obturator nerve is reliable, contrary to the femoral paravascular block, and the block is more proximal, with theoretically a better coverage of the hip
• When combined with a sciatic block, take into account total dose of local anesthetic
• This is an advanced block and should only be performed by experienced practitioners because of potential severe complications

Contraindications:

• Significant coagulopathy; this is a deep block, and a psoas sheath bleeding may go unnoticed, and is not amenable to compression:
  • Single-injection or continuous psoas compartment block should be treated as neuraxial blocks with regards to coagulation issues
• Significant lumbar spine deformity, as the position of the lumbar plexus might be distorted

Technique using NS (Figure 141-3):

• Patient in lateral decubitus, side to be blocked up, nondependent lower extremity slightly flexed; stand behind patient
• Draw Tuffier's line (joining the iliac crests): line A
• Draw a line over the spinous processes (feel for the spine; the median skin fold can sag and ...