Lumbar Plexus Blocks (Psoas Compartment Blocks)

Lumbar plexus blocks aim at injecting a local anesthetic within the psoas compartment where the lumbar plexus lies. The child is placed in the semiprone position, resting on the non-operated side. Two sites for needle insertion can be used (42) (Figure 1): 1) the midpoint of the line joining the spinous process of L5 to the posterior iliac spine (modified Chayen's technique) or 2) the intersec-tion of the line joining the two iliac crests with the line parallel the major axis of the spine drawn from the posterior iliac spine (Winnie's technique). However, it should be noted that a slightly more medial site of puncture (1 cm medial to the intersection, on the intercristal line) improves the technique. With either approach, the insulated block needle is inserted at right angles to the skin until twitches are elicited in the quadriceps muscle.





          Figure 1. Direct lumbar plexus blocks

          A: Modified Chayen's technique
          B: Modified Winnie's technique
          1. Lateral cutaneous nerve of the thigh
          2. Femoral nerve
          3. Obturator nerve
          4. Posterior superior iliac spine
          5. Spinous process of L5