Subclavian triangle

Thesubclavian triangle (orsupraclavicular triangle,omoclavicular triangle,Ho's triangle), the smaller division of the posterior triangle, is bounded, above, by the inferior belly of theomohyoideus; below, by theclavicle; its base is formed by the posterior border of thesternocleidomastoideus.

Subclavian triangle
Subclavian triangle
Side of neck, showing chief surface markings. (Nerves are yellow, arteries are red.)
Details
Identifiers
Latin	trigonum omoclaviculare
TA98	A01.2.02.010
TA2	241
FMA	75021
Anatomical terminology [edit on Wikidata]

Its floor is formed by the first rib with the first digitation of theserratus anterior.

The size of the subclavian triangle varies with the extent of attachment of the clavicular portions of theSternocleidomastoideus andTrapezius, and also with the height at which theOmohyoideus crosses the neck.

Its height also varies according to the position of the arm, being diminished by raising the limb, on account of the ascent of the clavicle, and increased by drawing the arm downward, when that bone is depressed.

This space is covered by the integument, the superficial and deep fasciæ and theplatysma, and crossed by the supraclavicular nerves.

Just above the level of the clavicle, the third portion of thesubclavian artery curves lateralward and downward from the lateral margin of thescalenus anterior, across the firstrib, to theaxilla, and this is the situation most commonly chosen forligaturing the vessel.

Sometimes this vessel rises as high as 4 cm. above the clavicle; occasionally, it passes in front of the Scalenus anterior, or pierces the fibers of that muscle.

The subclavian vein lies behind the clavicle, and is not usually seen in this space; but in some cases it rises as high as the artery, and has even been seen to pass with that vessel behind the Scalenus anterior.

Thebrachial plexus of nerves lies above the artery, and in close contact with it. Passing transversely behind the clavicle are thetransverse scapular vessels; and traversing its upper angle in the same direction, thetransverse cervical artery and vein.

Theexternal jugular vein runs vertically downward behind the posterior border of the Sternocleidomastoideus, to terminate in thesubclavian vein; it receives the transverse cervical and transverse scapular veins, which form a plexus in front of the artery, and occasionally a small vein which crosses theclavicle from thecephalic.

The small nerve to the subclavius also crosses this triangle about its middle, and somelymph glands are usually found in the space.

Enlarged nodes in this triangle irrespective of size are categorized at N3 in the TNM classification for nasopharyngeal carcinoma.

Gallery

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Sternocleidomastoid muscle
Muscles of the neck. Anterior view.
Posterior triangle of the neck labeled. (Anterior triangles to the left. Occipital triangle labeled at center left.) )