ANATOMY OF NECK

Professor Con Yiannikas

Biomechanics of Head Motion

Cervical Dystonia

Anatomy

Motion of the Head on Neck

Cervical Dystonia

Anatomy

Missing Video

Lateral Tilt

Cervical Dystonia

Anatomy

Lateral tilt occurs between C0-C1

Rotation and Flexion

Cervical Dystonia

Anatomy

Rotation at C1-2, Flexion and extension mainly at C0-1

Biomechanics of Neck Movement

Cervical Dystonia

Anatomy

Range of Motion

Cervical Dystonia

Anatomy

Biomechanics of Neck Motion

Cervical Dystonia

Anatomy

Most lateral flexion and flexion/extension occur serially from C2 through C7.

Long muscles spanning these segments have great advantage in lateral flexion and in flexion/extension.

The majority of head rotation occurs at the atlanto-axial joint, so that muscles that act across this joint (e.g. obliquus capitis inferior, splenius capitis, SCM) have advantage in producing turning movements.

Rotation at C1-2 requires some extension and lateral tilt.

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Cervical Dystonia

Anatomy

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Extensor Group

Cervical Dystonia

Anatomy

Splenius Capitis

Splenius Cervicis

Semispinalis Capitis

Longissimus Capitis

Spinalis Capitis

(Erector Spinae)

Semispinalis Cervicis

Layer 1

Layer 2

Layer 3

Extensor Group

Cervical Dystonia

Anatomy

Working together extend the neck

Function

Tilt the head to the same side – splenius capitis, cervicis

Turn head to
- Same side – lateral muscles insert into mastoid
  - Splenius capitis, cervicis, Longissimus capitis
- Opposite side - medial muscles insert into occiput

Lateral Muscles

Cervical Dystonia

Anatomy

SCM

Trapzius

Splenius Capitis

Levator Scapulae

Scalenes

Lateral Muscles - Action

Cervical Dystonia

Anatomy

Rotates neck to opposite side
- SCM, Scalenus anterior

Elevates shoulder
- Levator scapulae, trapezius

Lateral neck flexion
- All

Neck extension
- Trapezius when acting together

Neck flexion
- Scalenus anterior when acting together

Anterior/Lateral Muscles

Cervical Dystonia

Anatomy

Platysma

Scalenus Anterior

SCM

Longus Colli

Anterior/Lateral Muscles

Cervical Dystonia

Anatomy

When acting together

When acting individually

Action

- Lateral flexion
- Rotation to the opposite side

- Forward flexion

Rotation of Head

Cervical Dystonia

Anatomy

Attaching to skull
Unilateral contraction

Anterolateral muscles contralateral rotation

Trapezius
SCM

Posterolateral muscles ipsilateral rotation

Splenius capitus
Longissimus capitus
Splenius cervicus

Posteromedial contralateral rotation

Semispinalis capitis
Spinalis capitis

Contralateral Rotation

Cervical Dystonia

Anatomy

Scalenus anterior

Semispinalis capitis

Semispinalis cervicis

Spinalis cervicis

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Ipsilateral Rotation

Cervical Dystonia

Anatomy

Splenius capitis

Splenius cervicis

Longissimus capitis

Sub-occipital

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Lateral Flexion

Cervical Dystonia

Anatomy

Lateral muscles acting in isolation

Lateral Flexion

Cervical Dystonia

Anatomy

Ipsilateral
- SCM
- Splenius capitis
- Splenius cervicis
- Levator scapulae
- Trapezius
- Scalenes
- Longus colli

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Extension

Cervical Dystonia

Anatomy

Posterior and posterolateral muscles acting together

Neck Extension

Cervical Dystonia

Anatomy

Acting together
- Splenius capitis
- Splenius cervicis
- Trapezius
- Longissimus capitis
- Semispinalis muscles

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Flexion

Cervical Dystonia

Anatomy

Anterior muscles acting together

Neck Flexion

Cervical Dystonia

Anatomy

Acting together
- SCM
- Scalenes
- Longus Colli

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Chin flexion
- Platysma
- Submental muscles

Anatomical Landmarks

Cervical Dystonia

Anatomy

Mastoid tip- 1cm below and anterior-C1
Hyoid bone – C3
Thyroid Cartilage – C4-5
Cricoid cartilage – C6

Action

Scalenes

Cervical Dystonia

Anatomy

Origin

Anterior: C3-6

Medial: C1-7

Posterior: C3-7

Insertion

Anterior: First rib

Medial: First rib

Posterior: Second rib

Scalenes

Cervical Dystonia

Anatomy

Action

Lateral neck flexion

Elevation of first and second rib

Rotation of neck to opposite side (Scalenus anterior)

Scalenes

Cervical Dystonia

Anatomy

The scalenus anterior and medius muscles lie immediately anterior and posterior to the plexus in the interscalene region and then insert onto the first rib.

The upper, middle and lower trunks are enclosed within the interscalene fascial sheath as they emerge between the scalene muscles.

Scalenes

Cervical Dystonia

Anatomy

Missing Video

Scalenes EMG

Cervical Dystonia

Anatomy

Missing Video

Levator Scapulae

Cervical Dystonia

Anatomy

Origin

First to the fourth cervical vertebrae.

Insertion

Medial edge of the scapula, between the superior angle and the root of the spine.

Levator Scapulae

Cervical Dystonia

Anatomy

Action

Acts as a checkrein for the bent head

Levator Scapulae & Neck Motion

Cervical Dystonia

Anatomy

Left Lateral Flexion

Left U Trapezius, SCapitus and Levator Scapulae

Left U Trapezius,
Right SCapitus , Levator Scapulae

Bilateral U Trapezius
Scapitus, Levator Scapulae

Right Rotation

Extension

Levator Scapulae

Cervical Dystonia

Anatomy

Posterior Surface Anatomy

Line from acromium to midline and inferior
Feel the edge of the spine
Above and below is infra and supraspinatus fossae
Follow spine to midline (T3 level)
Above that along the medial border

Missing Video

6. Line obliquely from there to transverse process of C1-4 (below and anterior to splenius capitus)

Levator Scapulae EMG

Cervical Dystonia

Anatomy

Missing Video

Splenius Capitis

Cervical Dystonia

Anatomy

Splenius capitis forms part of the floor of the posterior triangle of the neck, above and behind levator scapulae; it is deep to the rhomboideus and trapezius.

Origin

- It is attached proximally to the lower half of the ligamentum nuchae, spinous processes of C7 to T4 and intervening supraspinous ligaments.

Insertion

- It is attached proximally to the lower half of the ligamentum nuchae, spinous processes of C7 to T4 and intervening supraspinous ligaments.

Splenius Capitis

Cervical Dystonia

Anatomy

Action

Individually
- Extends the head and neck, accompanied by lateral flexion of the neck and rotation of the face to the same side.

Together
- Pure extension

Splenius Capitis/Cervicis

Cervical Dystonia

Anatomy

Midway between the inion and mastoid process
From the same attachment forward is SCM
Runs obliquely to spinal processes of C7 to T3
Cervicis runs lateral border and underneath capitus anterior to levator scapulae.

Surface Anatomy

Splenius EMG

Cervical Dystonia

Anatomy

Missing Video

Sternomastoid

Cervical Dystonia

Anatomy

Unique Action

Extends the head and flexes neck when longus colli relaxed

Flexes head and cervical spine if deep flexors [longus colli] are contracted

Sub-Occipital Triangle

Cervical Dystonia

Anatomy

Obliquus Capitis

Rectus Capitis

Sub-Occipital Triangle

Cervical Dystonia

Anatomy

Rectus capitis posterior major and the superior and inferior oblique muscles bound this anatomical region.

Play a large role in the fine control of head movement.

Involved in rotation of the head , extension or lateral flexion.

Relations
- Vertebral Artery
- Greater Occipital nerve

Sub-Occipital Triangle

Cervical Dystonia

Anatomy

Triangle between C1 transverse process (below and behind mastoid), C2 and occiput.

Pass through Trapezius, Splenius capitus (more lateral) and semispinalis capitus (more medial) to reach it.

Splenius Capitis

Semispinalis

Rectus Minor Major

Obliquus Superior

Obliquus Inferior

Sub-Occipital Triangle

Cervical Dystonia

Anatomy

The C2 level is a plane 2.5 cm below the mastoid process

Midway between the posterior border of the sternocleidomastoid and the dorsal midline.

Depth of 3.0-3.5 cm.

Obliquus Capitis Superior

Rectus Capitis Major

Obliquus Capitis Inferior

Structures to Avoid

Cervical Dystonia

Anatomy

Brachial Plexus

From the intervertebral foramina, the 5 roots of the brachial plexus exit above the transverse processes of the corresponding cervical vertebrae and traverse through the interscalene groove before entering the floor of the posterior triangle of the neck.

The upper, middle and lower trunks are enclosed within the interscalene fascial sheath as they emerge between the scalene muscles.

The Interscalene Groove

Cervical Dystonia

Anatomy

The interscalene groove lies immediately behind the lateral border of the clavicular head of the sternocleidomastoid muscle at the level of the cricoid cartilage (C6)

Approximately 1cm above the separation of the sternal and clavicular heads of the sternocleidomastoid muscle.

Structures to Avoid

Cervical Dystonia

Anatomy

Brachial Plexus

The BP lies inferior to a line from the posterior margin of the sternomastoid at the level of the cricoid cartilage to the midpoint of the clavicle

Structures to Avoid

Cervical Dystonia

Anatomy

Brachial Plexus

The BP lies inferior to a line from the posterior margin of the sternomastoid at the level of the cricoid cartilage to the midpoint of the clavicle. Scalenus medius is behind and above line.