The patient is placed in the lateral position with the side to be anaesthetized turned upwards

A curved array transducer (6-2 MHz) is placed in the transverse plane at the abdominal flank immediately cranial to the iliac crest

The transducer is moved dorsally keeping the transverse orientation until the QL muscle is identified with its attachment to the lateral edge of the transverse process of the L4 vertebral body

With the psoas major muscle (PM) anteriorly, the erector spinae muscle (ESM) posteriorly and the QL muscle adherent to the apex of the transverse process, a well recognizable pattern of a shamrock with three leaves can be seen:

The transverse process of vertebral body L4 is visualized as the stem of the shamrock. The three leaves are the muscles: quadratus lumborum, psoas major, and the erector spinae muscle.

The needle is inserted in-plane to the transducer (lateral edge) and the tip of the needle is advanced through the QL muscle, penetrating the ventral proper fascia of the QL muscle and LA is finally injected between the QL and PM

Hanson NA & Auyong DB: Systematic ultrasound identification of the dorsal scapular and long thoracic nerves during interscalene block. Reg Anesth Pain Med 38: 54-57 (2013)

Analgesia of abdominal visceral and somatic pain

The subcostal, ilioinguinal and iliohypogastric nerves are sandwiched between the QL muscle and the psoas major muscle (PMM)

The subcostal nerve (T12), ilioinguinal nerve (L1) and iliohypogastric nerve (L1) run across the anterior side of the quadratus lumborum (QL) muscle between the QL muscle and the transversalis fascia (TF)

The upper two of the three spinal nerve root branches of the long thoracic nerve typically pierce the middle scalene muscle together with the dorsal scapular nerve

It is important to visualize and/or stimulate the long thoracic and dorsal scapular nerves with electrical nerve stimulation during the performance of an interscalene brachial plexus block

At the level just below the clavicle, the long thoracic nerve runs across the serratus anterior muscle between the major psoas muscle and the pleura

The long thoracic nerve origins from the spinal nerve roots C5, C6 and C7

The upper two roots typically pierce the middle scalene muscle and the lower passes anterior to the muscle

The components of the nerve enter the axilla behind the brachial plexus and descend approximately in the midaxillary line; it runs on the superficial surface of the serratus anterior muscle which it innervates.

Place the patient supine

Place the high-frequency linear probe in the axial plane and visualize the C5 and C6 spinal nerve roots in the interscalene groove between the anterior and middle scalene muscles. Visualize the long thoracic and dorsal scapular nerves inside the middle scalene muscle posterior to the interscalene groove (see second next page)

Advance the needle with in-plane technique from the posterior end of the probe. Confirm the identity of the long thoracic and dorsal scapular target nerves with electrical nerve stimulation

Inject 5 mL of local anaesthetic until complete perineural spread around the target long thoracic nerve