7.04 Bones and Joints of the Neck Flashcards
understand the following points: - typical and atypical cervical vertebrae - ligaments of neck - joints of upper cervical spine - joints of lower cervical spine range of movement
How are the structures of the neck organised?
Structures in neck are divided by layers of fascia into compartments for
- bones (vertebrae) and muscles
- viscera (& cartilages)
- vessels
What are the 4 layers of the deep cervical fascia?
- Investing layer
- Pretracheal layer
- Prevertebral layer
- Carotid sheath
In the following image, what do each of the colours represent?
- Grey (along the outside) - superficial fascia
- Red - investing layer
- Blue- pretracheal layer
- Orange- prevertebral layer
- Brown- carotid sheath
What resides in the pre-tracheal layer of deep fascia?
Longitudinal visceral structures: trachea and oesophagus and the thyroid gland around it
Where is the carotid sheath located? What resides in it?
Behind the structures of the pre-tracheal layer and to either side of it (there are 2 carotid sheaths)
It contains the major vessels and nerves transversing through the neck:
- common carotid artery medially
- laterally the internal jugular vein
- Tucked in between and behind them is the vagus nerve.
What can be said about the carotid sheath that is surrounding the internal jugular vein?
The sheath surrounding the vein is looser and thinner to allow for the vein to extend.
Where do the majority of the muscles of the neck reside? Why is this so?
What layer of fascia surrounds them?
Between the transverse processes and spinal process (transversospinal gutter) of the cervical vertebrae.
The muscles in the neck are extensions of the erector spinae muscles.
They are located behind the transverse process because centre of gravity is to the front of the head (the muscles are thus important for erect posture - extension of the head).
These muscles are surrounded by the prevertebral fascia
Describe the arrangement of the investing layer of fascia. What does it contain?
Arranged like a collar around the whole neck (relatively superficially)
Surrounds the sternoclenoimastoid muscle anteriorly and trapezius muscles posteriorly
Between which structures does the bracheal plexus emerge from the neck (and the subclavian artery transverse as well)
The scalene muscles at the top of the transverse processes are very imporatnt
- Scalenus anterior attached to the anterior part of the transverse process
- Scalenus medius: attached to the transverse/lateral processes aspect
They create an interval for the bracheal plexus to emerge from the neck as well as the subclavian artery.
What and where is the ligamentum nuchae?
It is a very prominent band of filamentous ligamants in the neck
It is formed by the tendinous insertions of the muscles coming towards the midline in the posterior part of the neck.
It is very powerful helping to maintain posture of the head (it obscures being able to feel the spinous processes of the cervical processes above C6)
What are the main bones and cartilages making up the neck? (5 structures)
- Cervical vertebrae
- Hyoid Bone
- Thyroid cartilage
- Cricoid Cartilage
- Tracheal cartilages
What verebrae make up the cervial spine? What can be said about the first two, and the last one?
C1-C7
C1 and C2 are atypical: atlas and axis respectively
C7 is also aytypical: prominens
What are the anatomical regions of the neck? Do they hold clinical significance?
No clinical significance
Posterior
- Back of the neck/Vertebral region
- Posterior triangle
- Sternomastoid region
Anterior
- Anterior triangle
- Root of the neck
Describe the curvature of the cervical spine. How and when is it formed?
Lordosis
The curve develops at about 6-9 months (enables support of the head)
‘Postvertebral’ muscles extend the head on the neck, extend the cervical spine & help maintain cervical lordosis.
Is cervical lordosis achieved through the shape of the verebrae? Explain
No it is a due to due to the shape & size of I-V discs (wedged shape disc)
How does the secondary cervical lordosis develop? Explain this in relation to the centre of gravity through the neck
The line of gravity passes anterior to the occipital chondyles (the arciculation of the head and neck) this means there is always a tendancy for the head to rotate forwards under gravity.
muscles of the neck hold up the head against this graviational pull eventually leading to reshaping of the IV discs
Which of the cervical vertebrae are considered typical cervical verebrae?
C3-C6
They get progressively larger going down
Describe the features of a typical cervical verebrae [5 features]
Label them
- Have a transverse mass with anterior & posterior tubercles
- Contains transverse foraminae (holes in transverse processes)
- Have bifid spinous processes
- Articular surfaces oriented at around 45 degrees
- ‘Uncinate’ (hook-like) processes on bodies C3-6
What is the significance of the transverse foramen?
As the transverse processes comes out, it has a hole (transverse foramen) providing a protective pathway for the vertebral artery.
Laterally as it terminates: tubercle located anteriorly and posteriorly and a bar of bone linking them (remnants of rib process - each vertebra irrespective of the level retains a rib element and only develop to ribs in throacic spine).
What is the significance of having a bifud spinous process?
To increase surface area for muscle and ligamentous attachment
Why is it useful for the vertebra of the neck to have unicinate processes on the body of C3-C6?
They guide movement of vertebra in an anterior-postero direction (back and forth)
Describe the features of the first atypical cervical bone C1
Called the Atlas
- It has no verebral no body
- It has anterior & posterior arches
- It has an important facet for dens
- Saucer-shaped upper surfaces for occipital condyles = forms the atlanta-occipital joint
- Has the long(est) transverse process
Describe the features of the second atypical cervical bone C2
Axis
- Has a very prominant superior process called the dens (odontoid process)
- this is the developmental body C1
- Surfaces on dens for articulation with anterior arch of atlas
- Strong spinous process
Vertebral column commonly shows variations that reflect developmental changes. Where do the mainly occur and what are the main types?
Occur at transitional regions; e.g. cranio-cervical, cervico-thoracic
- Cervical rib (elongation of the C7 anterior tubercle into a rib) It may terminate as a fibrous bands or articulate with the rib 1 and is referred to a cervical rib. Commonly associated with other anomalies at various levels. (Cranial shift)
- Occipitalisation of the atlas: Where the cervical ribs articulate up
- There can be a rib on L1 too (caudal shift)
Prevertebral muscles located anteriorly, deep to prevertebral fascia (across the front of the vertebral columns)
What is the largest of these muscles? Describe it and what it does
longus colli
It attaches to the anterior aspects of the vertebral bodies and discs
- helps maintain curvature of cervical spine
- Provides access to cervical discs & spinal cord in surgery
The anterior tubercle of C6 is often referred to as the carotid tubercle. Why is this?
Because the common carotid artery may be compressed by how large it is
Describe the path of the vertebral artery up the neck
It travels into C6 (C7 is too low for it) and through the transverse foraminae upwards and asses out towards laterally projecting transverse foramen of C1 and into the foramen magnum and joining partner on the other side
Describe the spinal cord of the cervical region
- Follows same pattern as back
- But nerve roots short & horizontal
- C1 & C2 pass behind ‘facet’ joints
- Effects of aging – osteophytic outgrowths
Describe the intervertebral discs of the cervical region
Thick IV discs with central nucleus; form cervical lordosis.
Annulus and nucleus (as with lumbar discs). Relative largest throughout vertebral column. Prevent forward slip and rotation.
Uncinate processes (‘Uncovertebral joint’ – ‘of Luschka’) form on superior margins of body – guide movement.
Describe prolapse in the cervical spine
Less common than lumbar spine due to structure & loading
- Usually trauma related in F/E +/- rotation
- May impinge on cord +/- nerve roots in vertebral canal
Describe the facet joints of the cervical spine
- Plane synovial joints, capsule innervated by posterior rami
- Oriented at 45 degees between coronal & horizontal planes (more horizontal in childhood).
- Permit flexion/extension + rotation
- Look for symmetry of facet surfaces (shingling) on CT (approximate very well)
What kind of injury is likely to affect the facet joints? Which direction is it most susceptible to this injury?
Whiplash injury- acceleration of head in an antero/posterior direction
= Injury of facet capsule & articular surfaces, + supporting ligaments (facet surfaces become compressed against each other)
Particularly susceptible to compression injury in hyperextension
Describe the atlanto-occipital joints
2 lateral synovial joints between occipital condyles and upper surfaces on atlas (Deep concave surfaces where occipital condyles articulate)
What is the ligament that stabilises the median pivot joint between the dens and anterior arch of the atlas? What is its significance?
The synovial joint in front and the dens is held in position by the transverse ligament.
It prevents tilting backwards of the dens into the vertebral canal (given about 3mm of A/P movement).
(stabilises dens, prevents posterior translation of dens into vertebral canal)
What are the two ligaments between the atlas and the occipital bone?
- Posterior atlanto-occipital membrane
- Anterior atlanto-occipital membrane
Where are the alar ligaments? What is their function?
Alar ligaments (very strong ‘check’ range of rotation of atlas around dens)
- susceptible to injury when head flexed & rotated + muscles relaxed
Where is the apical ligament? What is it derived from?
Band retained from the notochord
It sits above the alar ligaments on top of the dens connecting it to the occipital bone
Explain the effect of aging on the cervical spine
- Water content of nucleus reduces with age (90%-~65%) as does ROM
- Cervical discs degenerate earlier than lumbar
- Compression of anterior vertebral body – vertebral wedging, reduces lordosis
- Osteophytes may develop from uncinate processes & facet surfaces –irritate nerve roots & possibly occlude vertebral artery
Explain Hangman’s Fracture
Rare to fracture the Dens, usu. bilateral fracture of pedicles so the separated bone slides forwards like a spondolisthesis
What is Jefferson’s Fracture?
A bone fracture of the anterior and posterior arches of the C1 vertebra, though it may also appear as a three or two part fracture caused by a fall to the top of the skull eg. diving
