Bones and Joints of the Neck Flashcards
How many cervical bones are there?
7
What is the name of the first cervical bone?
Atlas
What is the name of the second cervical bone?
Axis
What can happen to cartilages with age?
They can ossify
What are the posterior neck regions?
- Back of the neck/Vertebral region
- Posterior triangle
- Sternomastoid region
What are the anterior neck regions?
- Anterior triangle
- Root of the neck
What does sternocleidomastoid do?
Rotates and flexes the neck.
What lies deep to sternocleidomastoid?
Nerves
What forms the roof of the neck?
The lower part of sternocleidomastoid, giving direct access to the thorax.
What are anterior and posterior to sternocleidomastoid?
Anterior and posterior triangles.
Where does the anterior triangle extend from?
Base from above across the mandible to down below to the root of the neck.
Where does the posterior triangle extend?
- Its apex is located above just behind sternomastoid and broadens out into a base below.
- It’s important in transmitting structure to the upper limb and back (nerves, arteries and veins).
- E.g. brachial plexus passes via posterior triangle into upper limb.
What is the posterior triangle important in transmitting?
Nerves, arteries and veins to the upper limb and back
What passes via the posterior triangle to the upper limb?
Brachial plexus, arteries and veins.
What are the 5 different fascial layers of the neck?
- Superficial fascia
- Deep cervical fascia (4 layers):
- Investing layer
- Pretracheal layer
- Prevertebral layer
- Carotid sheath
What sits in the carotid sheath?
Common carotid, internal jugular vein and vagus nerve tucked behind.
What does the investing layer invest?
Sternomastoid and trapezius.
Why is the fascia of the carotid sheath thin and expansible?
To allow for distension of the internal jugular vein.
What effect do the fascial layers have on infection in the neck?
They allow blood, pus and infective material to track up or down, but are partitioned off by the fascia.
What shape does the cervical spine have?
Lordosis
Why does the cervical spine have a lordotic curve?
Due to the shape and size of the IV discs
How is the cervical lordosis maintained?
‘Postvertebral’ muscles extend the head on the neck, extend the cervical spine & help maintain cervical lordosis.
How does the lordotic curve develop?
- As posterior neck muscles develop, infant is able to lift its head up, creating a secondary curvature in the cervical spine, referred to as a lordotic curve.
- This is primarily due to the shapes of the IV discs, not so much due to the vertebrae themselves.
Why does the head tend to rotate forwards?
- Because the centre of gravity tends to sit anterior to the axis of rotation.
- Hence why powerful posterior extensor muscles are required to maintain position of the head.
What are the transverse masses off the cervical vertebrae?
Anterior and posterior tubercles joined by the transverse bar.
What are the transverse foraminae?
The hole located in the transverse mass between the anterior and posterior tubercles.
How is the transverse mass positioned?
Not positioned directly laterally, rather somewhat oblique.
What does the transverse foramen transmit?
Vertebral artery
Why are the spinous processes of the cervical spine bifid?
Because there are so many muscles and ligaments trying to gain attachment that it increases its surface area to allow for attachment.
Which cervical vertebra has the longest spinous process?
C7 (atypical)
Why is C7 an atypical vertebra?
Atypical because its much bigger and has much more prominent spinous process
What is the angle of the cervical spinous processes ?
45 degrees
Which cervical vertebrae have uncinate processes?
C3-C6
Which vertebrae are typical vertebrae?
C3-C6
What are uncinate processes?
Uncinate processes are on the lateral sides of the bodies on the typical vertebrae (C3-C6), responsible for keeping movements in a sagittal plane – flexion/extension.
What do the lateral vertebral muscles attach to?
Anterior and posterior tubercles of transverse processes.
What are the lateral vertebral muscles?
Scalenes
What are the attachments of the scalenes?
Attach from typical vertebra and attach to the rib.
What are the 3 scalene muscles?
Anterior, medius and posterior
Which scalene is a key landmark in the neck?
Scalenus anterior - arises from anterior tubrcle and attaches to first rib.
Where does scalenus medius originate from?
Posterior tubercles.
What sits on the anterior surface of scalenus anterior?
Phrenic nerve
What passes between scalenus anterior and medius?
Subclavian artery and brachial plexus.
Where are the scalenus muscles located?
Deep to prevertebral fascia
Where are the prevertebral (anterior vertebral) muscles located?
Deep to prevertebral fascia
What comprises the prevertebral muscles?
Longus colli
What does longus colli do?
Maintains the curvature of cervical lordosis
What do the prevertebral muscles provide access to?
Cervical spinal cord - these muscles will need to be separated to provide a neurosurgeon with access to the cervical cord through the anterior aspects of the vertebral column and IV discs.
What are the 2 variants of the cervical vertebral column?
Cranial and caudal shift.
What can be a consequence of cranial shift?
- C8-T1 lower trunk coming up from the thorax and then (with a cervical lift) may become trapped or compressed in particular movements.
- Cervical ribs may have consequences for entrapment of brachial plexus. This will affect movements of the hand and sensory problems at T1 dermatomes (medial aspect of arm).
What are the features of the atlas?
- No body
- Anterior & posterior arches
- Facet for dens
- Saucer-shaped upper surfaces for occipital condyles
- Long(est) transverse process
What are the features of the axis?
- Dens (odontoid process) –developmental body C1
- Surfaces on dens for articulation with anterior arch of atlas
- Strong spinous process
What is special about the spinous process of C2 (axis)?
- 2nd cervical vertebra must be kept stable for rotation of C1 around the dens
- Therefore a mass of muscles stabilise it
What are the features of cervical nerve roots that make them different?
Nerve roots are short & horizontal
True or false: the spinal cord and nerves follow a different pattern to the back?
False - they follow the same pattern.
What do the C1 and C2 nerve roots pass behind?
Facet joints
What do the nerve roots of C3 and beyond pass between?
Face joints and body
What are the 2 important arteries of the neck?
- Common carotid
- Vertebral artery
What does the common carotid bifurcate into?
External (posterior) and internal) anterior.
What is the difference between the internal and external carotid arteries?
The external gives off branches.
What protects the vertebral artery?
Transverse foraminae
Why is the anterior tubercle of C6 (the carotid tubercle) an important landmark?
Because the common carotid can be compressed against it.
Why is the C4 vertebra an important landmark?
It’s the bifurcation of the common carotid and the upper border of the thyroid cartilage.
What are the inferior joints of the cervical spine?
Joints between C2-C7 comprising the IV discs and facet (zygapophyseal) joints.
What are the superior joints of the cervical spine?
Suboccipital joints:
- Atlanto-occipital (0-C1)
- Atlanto-axial (C1-2)
What creates the cervical lordosis?
The IV discs.
Where are the largets IV discs in the vertebral column relatively?
In the cervical spine.
What do the IV discs of the cervical spine prevent?
Forward slipping and rotation.
What are the uncovertebral joints?
The joints between the uncinate process above and below between C3 and C7. They allow for flexion and extension and limit lateral flexion in the cervical spine.
Are the uncovertebral joints synovial?
No
What do the uncinate processes protect?
IV discs
What happens to the uncinate processes with aging?
As disc disappears with ageing, uncinate processes rub together, stimulating osteophytes
Can IV disc prolapse occur at the cervical level?
Yes, usually in F/E +/- rotation. May impinge on cord +/- nerve roots in vertebral canal.
What are the facet joints?
Plane synovial joints
What is the facet joint capsule innervated by?
Posterior rami
What is the orientation of the facet joints?
Oriented at 45° between coronal & horizontal planes (more horizontal in childhood).
How can the facet joints be injured?
- Whiplash injury - acceleration of head in an antero/posterior direction
- Injury of facet capsule & articular surfaces, + supporting ligaments
- Particularly susceptible to compression injury in hyper-extension
What are the atlanto-occipital joints?
- 2 lateral synovial joints between occipital condyles and upper surfaces on atlas
- Loose fibrous capsule permits nodding movements (F/E). ROM = 15=20% of all cervical F/E
What are the atlanto-axial joints?
- 3 synovial joints specialised for rotation (no IV disc!)
- Median pivot joint between dens of C2 & anterior arch of atlas
- 2 lateral facet joints
- Allow approx. 50% of rotation of cervical spine
What holds the dens in position?
- Transverse ligament
- Only allows approx. 5˚ of anterior/posterior movement.
Why are people with rheumatoid arthritis in danger regarding the atlanto-axial joints?
- Transverse ligament holds dens in position – only allows approx. 5˚ of anterior/posterior movement.
- This joint allows 50% of the cervical rotation, the rest occurs through the remainder of the spine
What are the 4 ligaments of the cervical spine?
- Posterior and anterior atlanto-occipital membrane.
- Ligamentum nuchae
- Membrana tectoria
Where does the posterior atlanto-occipital ligament run?
Between the atlas and occiput.
Where do membrana tectoria and the anterior atlanto-occipital membrane run?
Between axis and occiput.
What is membrane tectoria a continuation of?
Posterior longitudinal ligament
What is ligamentum nuchae a continuation of?
Supraspinous ligament
What do all cervical ligaments resist?
Movements in the sagittal plane (flexion/extension)
What are the 3 specialised ligaments between the occiput and C2?
Transverse ligament, alar ligaments and cruciform ligament.
What does the transverse ligament do?
Stabilises dens, prevents posterior translation of dens into vertebral canal
What do the alar ligaments do?
Checks range of rotation of atlas around dens
When are the alar ligaments susceptible to injury?
When head flexed & rotated + muscles relaxed
What does the cruciform ligament do?
Prevents the dens from moving posteriorly into the spinal canal.
What are the effects of aging on the cervical spine?
- Water content of nucleus reduces with age (90%-~65%) as does function
- Cervical discs degenerate sooner than lumbar
- Compression of anterior vertebral body – vertebral wedging, reduces lordosis
- Osteophytes may develop from uncinate processes & facet surfaces – may irritate nerve roots & occlude vertebral artery
What is a Hangman’s fracture?
- A special type of extension fracture of the axis where both pedicles are fractured.
- Typically seen when drive of a vehicle is in a head on collision and not wearing a safety belt.
What is a Jefferson’s fracture?
- Mechanism: Fall onto vertex of skull e.g. dive into shallow water.
- Bilateral fracture anterior arch + pedicle
