Foundation Posterior Triangle 2024 PDF

Triangles of the neck I Lecture ID # 9018 By Dr. Sampath Madhyastha Sunday, 15th December 2024; 11.10 to 12 noon Objectives 1. Describe the boundari...

Triangles of the neck I Lecture ID # 9018 By Dr. Sampath Madhyastha Sunday, 15th December 2024; 11.10 to 12 noon Objectives 1. Describe the boundaries of posterior triangle (lateral cervical region) and its subdivisions 2. List the contents of the posterior triangle and its subdivisions 3. Describe the contents of the posterior triangle 4. Describe the clinical importance of major structures at the posterior triangle Sternocleidomastoid muscle (SCM) Origin: Sternum and Clavicle Insertion: Mastoid process and superior nuchal line of the occipital bone Nerve supply: Spinal part of the accessory nerve + ventral rami of C2, C3 Actions: Acting unilaterally (one side) it turns the face to the opposite side and downward movement of the head towards the shoulder of same side. Acting bilaterally (of both sides) draws the head forward. Clinical Anatomy: Torticollis: deformity in which head is bent to the affected side while the face (or chin) turns to the opposite side (If the right sternomastoid is paralyzed, the face is turned towards the left side & head is tilted towards right side). Posterior triangle Boundaries of the Posterior triangle Roof: The roof is formed by skin, platysma Anteriorly by the posterior border of sternocleidomastoid and investing layer of deep cervical muscle fascia. Between platysma and the deep Posteriorly by the anterior border of trapezius muscle fascia, there are nerves (great auricular Inferiorly (base) by the middle 1/3 of the clavicle nerve, lesser occipital nerve, transverse Superiorly (apex): It is at the superior nuchal line of the cutaneous nerve of the neck and occipital bone between the attachments of the supraclavicular nerve) and external sternomastoid & trapezius muscle. jugular vein.  Lesser occipital nerve Great auricular nerve Transverse cutaneous nerve of the neck Supraclavicular nerve External jugular vein  External jugular vein Formation & termination Tributaries Transverse cervical vein Suprascapular vein Anterior jugular vein Posterior external jugular vein Oblique jugular veins The wall of the EJV is adherent to the fascia, where it pierces the deep fascia. If the vein is cut at this point, it cannot close due the traction exerted by the attached fascia. When the vein is exposed to atmosphere, which may cause fatal venous air embolism unless the cut end is occluded immediately Floor of the posterior triangle Deep to the prevertebral fascia, following muscles are Prevertebral fascia & prevertebral muscles present from above downwards Splenius capitis, Levator scapulae, Scalenus posterior and Scalenus medius. Vertically oriented semispinalis capitis is also seen above the splenius capitis. The scalenus anterior is not included in the floor, as it is overlapped by sternomastoid muscle. SEMISPINALIS CAPITIS SPLENIUS CAPITIS Splenius capitis LEVATOR SCAPULAE Levator scapulae SCALENUS POSTERIOR SCALENUS Scalenus posterior ANTERIOR Scalenus medius SCALENUS MEDIUS Subdivision of the posterior triangle Occipital triangle Inferior belly of the Omohyoid muscle Subclavian/Supraclavicular triangle Contents of the posterior triangle Occipital triangle 1. The spinal part of the accessory nerve 2. The 3rd and 4th cervical nerves, 3. Cutaneous branches of the cervical plexus emerging at nerve point 4. Upper trunk of the brachial plexus 5. Superficial cervical artery/transverse cervical artery Subclavian triangle: 1. The third part of the subclavian artery, transverse cervical and suprascapular arteries 2. Trunks of the brachial plexus 3. Supraclavicular lymph nodes 4. Nerves: Dorsal scapular, Long thoracic Suprascapular nerves and Nerve to subclavius 5. Terminal part of the external jugular vein Transverse cervical artery Brachial plexus Suprascapular artery Subclavian artery Subclavian artery Brachial plexus Brachial plexus Anesthesia: For brachial plexus block the anesthetic agent is injected around the trunks just above the midpoint of the clavicle Supraclavicular lymph nodes (Virchow’s nodes) The left supraclavicular nodes are enlarged in cancers of the stomach, colon, testis, lung or breast. These nodes are called Virchow’s nodes (enlarged in cancer of stomach- Troisier’s sign) Midline structures of the neck: 1. Symphysis menti Symphysis menti 2. Submental lymph nodes on Mylohyoid muscle mylohyoid muscle 3. Body of the hyoid bone Body of the hyoid bone 4. Thyrohyoid membrane Thyrohyoid membrane 5. Laryngeal prominence (Adam’s apple) Laryngeal prominence 6. Cricoid cartilage Cricoid cartilage 7. Isthmus of the thyroid gland Isthmus of the thyroid gland 8. Inferior thyroid vein 9. 2nd to 4th tracheal ring 2nd to 4th tracheal ring 10. Suprasternal space of Burns (jugular venous arch, lymph Sternal notch nodes, interclavicular ligament, sternal head of sternomastoid muscle) Take Home Message Boundaries of the Posterior triangle → Anteriorly by Sternocleidomastoid, Posteriorly by Trapezius, Base by middle one third of the clavicle. Roof of the Posterior triangle → Ski, Platysma, External jugular vein, Great auricular, supraclavicular, lesser occipital nerves, Investing layer of deep cervical fascia. Floor of the Posterior triangle → Prevertebral fascia with following muscle deep to it-Scalenus medius, Scalenus posterior, Levator scapulae and Splenius capitis. Subdivision of the Posterior triangle → Inferior belly of the omohyoid muscle divides the posterior triangle into upper posterior triangle and lower subclavian triangle. Contents of the Posterior triangle → Third part of the subclavian artery, Trunks of the brachial plexus, Spinal accessory nerve (and also nerve to serratus anterior, suprascapular nerve and artery, transverse cervical and occipital arteries). External jugular vein → Formed by the union of posterior division of retromandibular vein and posterior auricular vein. It descends superficial to sternocleidomastoid muscle, pierces deep fascia and terminates in the subclavian vein. Its tributaries are posterior external jugular vein, oblique external jugular vein, suprascapular and transverse cervical veins.