Supraclavicular brachial plexus: ultrasound anatomy

Probe position

• Patient supine, head turned to the opposite side, ipsilateral arm adducted.
• Use a high-frequency linear probe in the supraclavicular fossa, just superior/posterior to the midpoint of the clavicle.
• Obtain a transverse or slightly oblique transverse view.

Structures on the ultrasound image

Key spatial relationship

Superficial
   Skin / subcutaneous tissue

      Brachial plexus
     (trunks/divisions)
            ○ ○ ○
              \
               \  posterolateral to
                [ Subclavian artery ]

                  First rib  ─────────  bright cortex + shadow
                  Pleura     ─────────  sliding echogenic line
Deep

How to recognize the plexus

1. Find the subclavian artery first.
2. Look lateral and posterior/superficial to it.
3. The plexus appears as several tightly packed hypoechoic circular or oval structures.
4. Identify the first rib deep to the plexus. Its acoustic shadow helps distinguish it from pleura.
5. Locate the pleural sliding line below the rib before any needle advancement.

The “corner pocket”

• the inferolateral subclavian artery, and
• the first rib.

Safety anatomy

• Pleura is close, commonly only 1-2 cm deep to the plexus. Do not advance a needle if the tip is not clearly seen.
• First rib is the protective backstop. Aim to keep the needle trajectory such that the rib remains between needle tip and pleura.
• Use color Doppler to identify vessels. The dorsal scapular and transverse cervical arteries may pass through or near plexus elements.
• A lateral-to-medial in-plane approach is commonly used, but technique should only be performed by clinicians trained in ultrasound-guided regional anesthesia.

Supraclavicular brachial plexus: USG anatomy

Probe position

• Supine patient, head turned away from the block side, arm adducted.
• High-frequency linear probe in the supraclavicular fossa, just above the midpoint of the clavicle.
• Start in a transverse/slightly oblique transverse orientation.

Structures to identify, superficial to deep

Key relation

                 Superficial
                      Skin

          Brachial plexus: ○ ○ ○
            posterolateral/superficial
                       to
              Subclavian artery: ●

                  First rib: ─────
                    Pleura: ~~~~~
                    Deep

Scan sequence

1. Identify the subclavian artery.
2. Find the first rib deep to it. Look for its bright cortex and acoustic shadow.
3. Confirm the pleural sliding deep to the rib.
4. Sweep lateral/posterior to the artery to identify the clustered plexus trunks/divisions.
5. Trace cephalad if needed: upper trunk = C5-C6, middle trunk = C7, lower trunk = C8-T1.

Important practical points

• The lower trunk is closest to the subclavian artery and pleura.
• The corner pocket lies between the inferolateral subclavian artery and the first rib, near the lower trunk.
• Always identify the first rib and pleura before needle insertion. The rib is the protective bony backstop; loss of visible needle-tip control risks pleural injury and pneumothorax.
• Color Doppler helps detect vessels, including vessels that may run among plexus elements.

Labeled ultrasound images: supraclavicular brachial plexus view

Read the image in this order

1. SA: subclavian artery, round and anechoic.
2. BP: brachial plexus, a cluster of hypoechoic round fascicles lateral/posterolateral to the artery.
3. 1st rib: bright curved line with acoustic shadow.
4. Pleura: sliding echogenic line deep to the rib.