7 – Scanning technique for the parasacral parallel shift

The curved array probe is placed on the upper half of the line connecting the posterior superior iliac spine and the ischial tuberosity. In this position the iliac bone line is a continuous hyperechoic line (see next page).

From this starting position the probe is parallel shifted infero-medially until the continuity of the iliac bone is disrupted. It is disrupted because the probe reaches the pelvic opening where the sacral plexus exits the pelvis – the greater sciatic foramen (see second next page).

With a slight caudal tilt of the probe, the sacral plexus becomes visible underneath the piriformis muscle (see second next page).

The needle is inserted from the lateral end of the probe and the needle tip is advanced until it reaches the target lumbar plexus (see second next page). Electrical nerve stimulation can be used to confirm the endpoint.

10-15 mL of local anaesthetic is injected in the fascial space between the piriformis muscle and the strong pelvic fascia.