Which block targets the lumbar plexus within the psoas muscle?

Which block targets the lumbar plexus within the psoas muscle?

• A. Fascia iliaca block
• B. Obturator nerve block
• C. Transpsoas (psoas compartment) block
• D. Femoral nerve block

Answer: (C)

The key idea is where the lumbar plexus sits and how the injection site reaches it. The lumbar plexus is embedded in the psoas major muscle as it forms and traverses the lumbar region. To block these nerves effectively, you place local anesthetic in the psoas compartment where the plexus lies. The transpsoas (psoas compartment) block specifically delivers anesthesia into that muscle compartment, directly affecting the lumbar plexus as it runs through the psoas. Other blocks target nerves outside that region: fascia iliaca block sits in the fascia over the iliacus to affect the femoral nerve (and sometimes lateral femoral cutaneous nerve) but does not reliably access the plexus inside the psoas; obturator nerve block targets only the obturator nerve; femoral nerve block targets the femoral nerve away from its passage within the psoas. Thus, the transpsoas block is the one that reaches the lumbar plexus within the psoas muscle.

The key idea is where the lumbar plexus sits and how the injection site reaches it. The lumbar plexus is embedded in the psoas major muscle as it forms and traverses the lumbar region. To block these nerves effectively, you place local anesthetic in the psoas compartment where the plexus lies. The transpsoas (psoas compartment) block specifically delivers anesthesia into that muscle compartment, directly affecting the lumbar plexus as it runs through the psoas.

Other blocks target nerves outside that region: fascia iliaca block sits in the fascia over the iliacus to affect the femoral nerve (and sometimes lateral femoral cutaneous nerve) but does not reliably access the plexus inside the psoas; obturator nerve block targets only the obturator nerve; femoral nerve block targets the femoral nerve away from its passage within the psoas. Thus, the transpsoas block is the one that reaches the lumbar plexus within the psoas muscle.