Contents of Subclavian Triangle
Definition and Boundaries
The subclavian triangle (also called the supraclavicular triangle) is the smaller lower subdivision of the posterior triangle, situated below the inferior belly of omohyoid.
| Boundary | Formed By |
|---|---|
| Superior | Inferior belly of omohyoid |
| Anterior | Posterior border of SCM |
| Inferior | Middle one-third of clavicle |
| Roof | Investing layer of deep cervical fascia + skin + superficial fascia |
| Floor | First rib, scalenus medius, scalenus anterior (medial wall) |
Contents
Arteries
| Artery | Details |
|---|---|
| Subclavian artery (3rd part) | Extends from lateral border of scalenus anterior to outer border of 1st rib; arches over 1st rib; gives no branches in this part |
| Suprascapular artery | Branch of thyrocervical trunk; crosses the triangle superficial to brachial plexus; accompanies suprascapular nerve |
| Transverse cervical artery (lower part) | Crosses through to trapezius |
Veins
| Vein | Details |
|---|---|
| Subclavian vein | Lies anterior and inferior to subclavian artery; separated from artery by scalenus anterior; receives external jugular vein |
| External jugular vein (termination) | Pierces investing fascia at lateral border of SCM; drains into subclavian vein |
Nerves
| Nerve | Details |
|---|---|
| Brachial plexus — upper trunk (C5, C6) | Emerges between scalenus anterior and medius; lies above and behind subclavian artery |
| Brachial plexus — middle trunk (C7) | Lies behind subclavian artery |
| Brachial plexus — lower trunk (C8, T1) | Lies on 1st rib, behind subclavian artery |
| Suprascapular nerve (from upper trunk) | Passes posteriorly across the triangle to supraspinous fossa |
| Nerve to subclavius (C5, C6) | From upper trunk; passes anteriorly, crosses subclavian vessels |
| Nerve to serratus anterior (Long thoracic, C5,6,7) | Descends on outer surface of serratus anterior (exits via posterior triangle floor) |
Lymphatics
- Supraclavicular lymph nodes lie along the transverse cervical vessels
- Left supraclavicular node = Virchow’s node (drains via thoracic duct)
Arrangement of Structures (Medial → Lateral at Root of Neck)
From medial to lateral, the key structures at the base of the subclavian triangle are:
- Scalenus anterior (medial wall)
- Phrenic nerve (on anterior surface of scalenus anterior)
- Subclavian vein (anterior to scalenus anterior)
- Subclavian artery 3rd part (lateral to scalenus anterior)
- Brachial plexus trunks (emerging between scalenus anterior and medius, above artery)
Clinical Significance
Cervical Rib:
- Accessory rib from C7 vertebra elevates the lower trunk of brachial plexus and the subclavian artery
- Compresses C8, T1 → medial forearm and hand tingling, weakness of intrinsic hand muscles
- Compresses artery → diminished radial pulse, Raynaud’s phenomenon
- Treatment: surgical resection of cervical rib
Subclavian Vein Cannulation:
- Subclavian vein accessible below clavicle at base of subclavian triangle
- Risk: pneumothorax, subclavian artery puncture, brachial plexus injury
Supraclavicular Brachial Plexus Block:
- Trunks are compactly arranged in the subclavian triangle
- Local anaesthetic injection here provides reliable upper limb anaesthesia