The Cervical And Thoracic Spine

Question 1

The cervical spine

Answer 1

There are seven cervical vertebrae. C1, C2 and C7 are referred to as atypical cervical vertebrae whereas C3-6 are fairly uniform and are referred to as typical

The key characteristics of typical cervical vertebrae are that they have a:
Body that is small and broad from side to side.
Large triangular vertebral (neural) foramen
Bifid spinous process (except C7)

Question 2

C1, The Atlas

Answer 2

C1, the atlas, is a bony ring that consists of an anterior and posterior arch connected by two lateral masses.

It is the widest cervical vertebra and does not have a vertebral body or a spinous process.

The vertebral arches are thick and strong and form a powerful lateral mass.

The anterior arch occupies 20% of the circumference of the ring and is the site of attachment of the anterior longitudinal ligament.

The posterior arch occupies 40% of the ring and contains the posterior tubercle which is a site of attachment of the ligamentum nuchae.

The articular facets are positioned on the lateral mass. The superior articular facets are cup-shaped and articulate with the occipital condyles of the skull, and the inferior articular facets articulate with the superior articular facets of the C2 vertebra.

The atlanto-occipital joint (between the occiput of the skull and the atlas vertebra) permits nodding of the head, and contributes 50% of the total range of flexion and extension of the head and neck.
The atlanto-axial joint (between the atlas (C1) and the axis (C2) vertebrae), is responsible for 50% of the total rotation of the head and neck.

Question 3

C2, the axis

Answer 3

C2 is known as the axis and provides the pivot on which the atlas (C1) rotates.

It is the strongest cervical vertebra and has a rugged lateral mass and a large spinous process.

The odontoid process, also known as the dens or odontoid peg, projects vertically upwards from the body of the axis.This is the vestigial remnant of the body of C1.

The dens is held in place by the transverse ligament of the atlas and acts as a pivot joint.

The apical ligament attaches between the odontoid process and the base of the skull superiorly.

The odontoid process and transverse ligament together prevent horizontal displacement of the atlas on the axis below.

Excessive movement between the C1 and C2 vertebrae is called atlantoaxial instability.

It can be congenital but more commonly it results from acute trauma or degenerative changes in rheumatoid arthritis.

Neurological symptoms can occur if the spinal cord or adjacent nerve roots become compressed.

Question 4

C7, the vertebra prominens

Answer 4

C7 is also known as the vertebra prominens.

It has the longest spinous process, which unlike the other cervical vertebrae, is not bifid.

The transverse process is large but the foramen transversarium is small and only transmits the accessory vertebral veins.

Question 5

Cervical spine allowing nerves to exit

Answer 5

In the cervical region, a groove for the spinal nerve runs across the superior aspect of the vertebral pedicle and then between the anterior and posterior tubercles of the transverse process.

The spinal nerve passes posterior to the vertebral artery which ascends through the foramina transversaria (plural of foramen transversarium) in C1-6, together with the vertebral vein and sympathetic plexus.

In the cervical region, however, each spinal nerve exits above its respectively- named vertebral body until the C7/T1 junction, where the C8 nerve root is the ‘exiting nerve root’.

The neural segments are also much more ‘in line’ with their respective vertebrae so the spinal nerve roots leave the cord more horizontally to pass through the intervertebral foramina.

This is of great importance when comparing the effect of intervertebral disc prolapse in the cervical spine with that in the lumbar spine, as there is no traversing nerve root in the cervical spine and it is the exiting nerve root that tends to be compressed by the disc

Question 6

Ligamentum nuchae (nuchal ligament)

Answer 6

Nuchal ligament is a thickening of the supraspinous ligament

It extends from the external occipital protuberance of the skull and the median nuchal line to the spinous process of C7.

From its anterior border, a fibrous lamina attaches to the posterior tubercle of the atlas and to the spinous processes of all seven cervical vertebrae. It is continuous inferiorly with the supraspinous ligament.
The roles of the ligamentum nuchae are:
To maintain the secondary curvature of the cervical spine

Question 7

The anterior and posterior longitudinal ligament

Answer 7

The anterior longitudinal ligament is stronger than the posterior longitudinal ligament.

It runs continuously from the tubercle of the atlas (C1 vertebra) to the sacrum and is united with the periosteum of the vertebral bodies.

Over the intervertebral discs, it is loosely attached and mobile. Its function is to prevent hyperextension of the vertebral column.

The posterior longitudinal ligament runs posterior to the vertebral bodies, from the body of the axis (C2 vertebra) to the sacral canal.

Superior to the axis, it continues as the tectorial membrane of the atlanto-axial joint (a strong band that covers the dens of the axis).

The posterior longitudinal ligament prevents hyperflexion of the vertebral column. Its main relevance clinically is that intervertebral disc prolapse tends to occur lateral to it i.e. a paracentral disc herniation

Question 8

Movements of the cervical spine

Answer 8

The cervical spine is one of the most mobile segments of the vertebral column (alongside the lumbar spine).

50% of the movement of ‘nodding the head’ takes place through flexion and extension of the atlanto-occipital joint (between the atlas [C1] and the occipital bone)

The remainder of the flexion-extension of the cervical spine takes place in the facet joints between the cervical vertebrae.

50% of the rotation movement of ‘shaking the head from side to side’ takes place between the atlas and axis at the atlanto-axial joint (C1-2) with the remainder taking place at the facet joints.

The cervical spine also permits approximately 45° of lateral flexion (moving your ear towards the tip of your shoulder), which occurs at the facet joints.

To facilitate these movements, the articulating facets in the cervical vertebrae are orientated in the coronal plane and at 45° to the axial (transverse) plane with the superior articulating process facing posterior and up, and the inferior articulating processes facing anterior and down.

Question 9

The thoracic spine

Answer 9

The key characteristics of the thoracic vertebrae are that they have:

Question 10

Orientation and movement of facet joints in the thoracic spine

Answer 10

The thoracic spine has limited flexibility compared with the cervical and lumbar spine because the rib cage is connected to each segment of the thoracic spine

The ribs attached to T1-T10 curve around to meet at the front of the body and either attach to the sternum (ribs 1-7), to the costal cartilages of the rib superior to them (ribs 8-10) or do not have an anterior attachment and terminate in the abdominal musculature (ribs 11 and 12).

Together, the thoracic spine, sternum and rib cage provide stability and protection for the heart, lungs, liver and other vital organs.

The ribs connected to T11 and T12 also provide protection for the kidneys in the retroperitoneum (posterior wall of the abdomen).

Question 11

Costal facets on vertebrae and connections of the vertebrae to the ribs

Answer 11

In addition to the superior and inferior articular facets that are present on all vertebrae, in the thoracic region there are costal facets located on the sides of each vertebra

They consist of cartilage-lined depressions which articulate with the heads of the ribs. The majority of thoracic vertebrae (T2-T8) have superior and inferior demi-facets (literally ‘half-facets’) on the sides of the vertebral body.

The superior demi-facet articulates with the head of the adjacent rib, and the inferior demi-facet articulates with the head of the rib below i.e. the T3 vertebra articulates with ribs 3 and 4 [or the rib articulates with the vertebra of the same number and the vertebra above].

There are some atypical vertebrae that possess whole facets:

Question 12

Cervical spondylosis

Answer 12

Cervical spondylosis is a chronic degenerative osteoarthritis affecting the intervertebral joints in the cervical spine.

The primary pathology is usually age- related disc degeneration, which is followed by marginal osteophytosis (osteophyte formation adjacent to the end plates of the vertebral bodies) and facet joint osteoarthritis.

The resultant narrowing of the intervertebral foramina can put pressure on the spinal nerves leading to radiculopathy.

Symptoms of radiculopathy include dermatomal sensory symptoms (e.g. paraesthesia, pain), and myotomal motor weakness.

If the degenerative process leads to narrowing of the spinal canal, this may instead put pressure on the spinal cord leading to myelopathy.

This is a less common outcome than radiculopathy, and may manifest as global muscle weakness, gait dysfunction, loss of balance and/or loss of bowel and bladder control.

These symptoms arise due to compression and dysfunction of the ascending and descending tracts within the spinal cord.

Question 13

Fractures of the Atlas

Answer 13

Jeffe

Question 14

Fracture of the axis

Answer 14

In a Hangman’s fr

Question 15

Whiplash injury

Answer 15

The head accounts for 7-10% of the total body weight. It is balanced on the cervical spine, which has high mobility and therefore low stability (as mobility and stability of joints are inversely related).

The cervical spine is therefore very prone to whiplash injury, which is a forceful hyperextension-hyperflexion injury of the cervical spine.

The classical mechanism is the patient’s car being struck from the rear leading to an acceleration-deceleration injury as follows:

Question 16

Chronic myo fasciae pain syndrome - secondary issue from whiplash

Answer 16

Chronic myofascial pain syndrome can sometimes develop as a secondary tissue response to disc or facet-joint injury.

There is a surprisingly high prevalence of chronic pain that results from whiplash injury, although secondary gain (e.g. financial compensation) may lead to prolongation of symptoms in a number of patients.

Sometimes whiplash can result in injury to the cervical cord, despite there being no accompanying bony fracture.

The cervical spine is highly mobile and the ligaments and capsule of the joints are weak and loose.

Hence, there can be significant movement of the vertebrae (e.g. subluxation or dislocation) at the time of impact, with return to the normal anatomical position afterwards. Soft tissue swelling may be the only visible feature on imaging.

A protective factor against spinal cord injury is that the vertebral foramen is large relative to the diameter of the cord. The normal diameter of the cervical spinal canal is 17-18 mm. The average diameter of the spinal cord in the cervical region is 10mm.

Question 17

Cervical IVD prolapse

Answer 17

Cervical disc prolapse with associated compression of nerve roots or spinal cord most commonly develops in the 30 to 50 year-old age group.

The mechanism of disc herniation is similar to that seen in the lumbar spine in that a tear develops in the annulus fibrosus of the disc, and the nucleus pulposus protrudes from the disc, with impingement onto an adjacent nerve root or the spinal cord

Sometimes sequestration occurs in which an extruded segment of nucleus pulposus separates from the main body of the disc and enters the spinal canal where it is ultimately resorbed over a period of weeks, with resolution of symptoms.

The discs in the cervical spine are not very large. However, there is also little space available for the exiting nerves (unlike in the lumbar spine) so even a small cervical disc herniation may impinge on the nerve and cause significant pain.

Cervical intervertebral disc prolapse may be spontaneous in origin or may be related to trauma and neck injury.

Symptoms are dependent on the site of the prolapse.

Paracentral prolapse may impinge on a spinal nerve leading to radiculopathy (compression of a spinal nerve, described in the section on cervical spondylosis above) whereas a canal-filling prolapse may lead to acute spinal cord compression.

Question 18

Cervical myelopathy

Answer 18

Cervical myelopathy
Cervical myelopathy is spinal cord dysfunction due to compression of the cord. It is caused by narrowing of the spinal (vertebral) canal.

A common cause is degenerative stenosis of the spinal canal caused by cervical spondylosis (degenerative osteoarthritis, see below).

This most commonly affects 50 –

Question 19

Thoracic cord compression

Answer 19

The commonest causes of thoracic cord compression are vertebral fractures (with bony fragments in the spinal canal) and tumours in the spinal canal.

Metastases to the thoracic spine are very common. The incidence of any cancer during a person’s lifetime is

Question 20

Vertebral osteomyelitis, discitis and epidural abscess

Answer 20

Pathogens can reach the bones and tissues of the spine by three routes:

Question 21

The brachial plexus - basics

Answer 21

The brachial plexus is divided into five parts: roots, trunks, divisions, cords and branches.

There are no functional differences between these parts; they are simply used to aid explanation of the brachial plexus.

At each neural level of the spinal cord, dorsal (sensory) roots enter the spinal cord and ventral (motor and autonomic) roots leave the spinal cord.

These roots converge to form a mixed nerve called a spinal nerve at the intervertebral foramen.

Each spinal nerve then divides into an anterior and a posterior ramus.

The trunks travel inferolaterally across the posterior triangle of the neck
Each trunk divides into two divisions within the posterior triangle of the neck. One division passes anteriorly and the other posteriorly so they become known as the anterior and posterior divisions.

There are therefore three anterior and three posterior divisions. These divisions leave the posterior triangle and pass into the axilla.

Once the anterior and posterior divisions have entered the axilla, they combine together to form three cords, named by their position relative to the axillary artery.

The three cords are the:

Question 22

Major branches of the brachial plexus

Answer 22

There are five major terminal branches and these tend to supply an entire compartment in the upper limb, although there is some overlap between them

The terminal branches are:
Axillary nerve

Question 23

Upper Brachial plexus injuries

Answer 23

Brachial plexus injuries can affect both motor function and cutaneous sensation within the upper limb.

Traction injuries may affect either the upper nerve roots or the lower nerve roots of the brachial plexus.

Both have characteristic findings:
Injuries to the upper brachial plexus usually result from an excessive increase in the angle between the neck and shoulder.

This may occur in trauma or during the birth of a baby if the shoulders become impacted in the pelvis (shoulder dystocia) and excessive traction is applied to the baby’s neck.

In an upper brachial plexus injury, the paralysed muscles are:

Question 24

Lower Brachial plexus

Answer 24

Injuries to the lower brachial plexus usually occur due to forced hyperextension or hyperabduction, such as when someone falls from a height and grabs onto a tree branch on the way down.

An alternative mechanism of injury is if the baby’s arm is delivered first and traction is applied to the arm to deliver the rest of the baby. Injury to the lower roots of the brachial plexus is known as Klumpke’s palsy

Nerve roots C8 and T1 are affected.

The weakness therefore principally affects the following movements:
C8: finger flexion / finger extension / thumb extension / wrist ulnar deviation
T1: finger abduction and adduction

The paralysis affects the intrinsic muscles of the hand and those flexors within the forearm that are supplied by the ulnar nerve (i.e. flexor carpi ulnaris and the ulnar half of flexor digitorum profundus). It also affects those muscles supplied by the C8 and T1 fibres within the median and radial nerves, so is not just a straightforward high ulnar nerve injury

The pattern of deformity classically presents as a ‘claw hand’ with hyperextension of all of the metacarpophalangeal joints (not just the ring and little finger seen in an ulnar nerve injury), flexion of the interphalangeal joints, abduction of the thumb and wasting of the interossei.

Question 25

Pectoralis major

Answer 25

The pectoralis major is the most superficial muscle in the pectoral region. It is triangular in shape and the origin is composed of a sternal head and a clavicular head

The clavicular head originates from the anterior surface of the medial clavicle.

The sternocostal head originates from the anterior surface of the sternum, the upper six costal cartilages and the aponeurosis of the external oblique muscle.

Pectoralis major inserts into the intertubercular sulcus of the humerus.

The fibres from the clavicular head overlap those of the sternal head and insert inferior to them in the intertubercular sulcus

Actions:

Question 26

Pectoralis minor

Answer 26

The pectoralis minor muscle lies deep to pectoralis major. Both muscles form part of the anterior wall of the axilla.

Pectoralis minor originates from the 3rd-5th ribs and inserts into the coracoid process of the scapula

Action: Pectoralis minor stabilises the scapula by drawing it anteroinferiorly against the thoracic wall.

Question 27

Serrated anterior

Answer 27

The serratus anterior muscle is located more laterally on the chest wall and forms the medial border of the axilla.

It originates as separate ‘slips’ from the lateral aspects of ribs 1-8

The fibres pass deep to the scapula and insert into the costal (rib-facing) surface of its medial border (the border nearest the vertebral column).

Action: Serratus anterior protracts the scapula. It also rotates the medial border of the scapula anteroinferiorly so that the glenoid cavity (site of articulation with the humerus at the shoulder joint) rotates upwards

This enables the upper limb to be abducted above 90° at the shoulder.

Serratus anterior also holds the medial border of the scapula against the ribcage.

Innervation: Long thoracic nerve (C5-7, directly from anterior rami of spinal nerves i.e. from the ‘roots’).

Question 28

Winging of the scapula

Answer 28

One of the actions of the serratus anterior is to ‘hold’ the scapula against the ribcage.

If the long thoracic nerve is damaged (and the serratus anterior is therefore paralysed), ‘winging of the scapula’ occurs, so called because of its winged appearance

The medial border of the scapula is no longer held against the chest wall so protrudes posteriorly.

This can be seen clearly when the patient is asked to place the palm of their hand on a wall and push; the force is transmitted back along their upper limb to the scapula which ‘lifts off’ the underlying ribs.

Alternatively, the patient can be asked to hold their unaffected shoulder with the hand of the affected limb and pull the unaffected shoulder forwards; this places traction on the scapula of the affected limb and elevates its medial border.

The most common cause of dysfunction of the long thoracic nerve is trauma. The long thoracic nerve is vulnerable to surgical trauma during a mastectomy with axillary clearance (excision of the breast and axillary lymph nodes for cancer) as it passes superficial to the serratus anterior muscle in the medial wall of the axilla and can be ‘stripped’ along with the axillary nodes and fat.

Also, a blunt trauma to the neck or shoulder causing sudden depression of the shoulder girdle, or wearing a heavy backpack, can both cause traction injuries to the long thoracic nerve.

Question 29

Coracobrachialis

Answer 29

The coracobrachialis muscle lies deep to the biceps brachii in the arm.

Coracobrachialis originates from the coracoid process of the scapula.

It passes through the axilla and inserts onto the medial side of the humeral shaft, at same the same level as the deltoid tubercle.

Action: Coracobrachialis flexes the arm at the shoulder and is also a weak adductor of the arm.

Innervation: Musculocutaneous nerve (C5-7 from the lateral cord of the brachial plexus)

Question 30

Subclavicus

Answer 30

The subclavius is small muscle, which is located directly underneath the clavicle, running horizontally.

It affords some minor protection to the underlying neurovascular structures (e.g. in cases of clavicular fracture or other trauma).

Subclavius originates from the junction of the 1st rib and its costal cartilage and inserts onto the inferior surface of the middle third of the clavicle

Action: Subclavius anchors and depresses the clavicle.

Innervation: Nerve to subclavius

Question 31

Deltoid

Answer 31

The deltoid muscle is a triangular muscle, shaped like the Greek letter delta: Δ.

It can be divided functionally into anterior, middle and posterior parts.

Deltoid originates from the anterior border and upper surface of the lateral third of the clavicle, and from the acromion and spine of the scapula.

It inserts into the deltoid tuberosity on the lateral surface of the humerus.

Actions:

Question 32

The Axilla

Answer 32

The axilla is a pyramidal space at the junction of the upper limb and the thorax.

It provides a passageway by which neurovascular and muscular structures can enter and leave the upper limb.

The axillary borders consist of 4 walls, an apex and a base

Apex (axillary inlet): lateral border of the first rib, superior border
of scapula, and the posterior border of the clavicle.

Question 33

Contents of the axilla

Answer 33

The contents of the axilla include muscles, nerves, vasculature and lymphatics:

Question 34

Lymph nodes of the axilla

Answer 34

The axillary lymph nodes are arranged into groups:

Anterior (pectoral) group: Lying along the lower border of the pectoralis minor behind the pectoralis major, these nodes receive lymph vessels from the lateral quadrants of the breast and the anterolateral abdominal wall above the level of the umbilicus.

Question 35

Axillary Lymphadenopathy

Answer 35

Axillary lymphadenopathy refers to enlargement of the axillary lymph nodes.

Causes include:

Question 36

Axillary artery

Answer 36

The arterial supply to the upper limb is delivered via five main vessels (proximal to distal):

Question 37

Axillary vein

Answer 37

The axillary vein is formed at the lower border of teres major from the union of the paired brachial veins (venae comitantes of the brachial artery) and the basilic vein

The axillary vein commences at the inferior border of the teres major muscle and ascends through the axilla anteromedial to the axillary artery.

It becomes continuous with the subclavian vein at the lateral border of the first rib.

Like the axillary artery, it is divided into three parts based on its relationship with the teres minor muscle.

The second and third parts of the axillary vein have tributaries that correspond with the branches of the axillary artery.

These include the thoracoacromial vein, lateral thoracic vein, subscapular vein, anterior circumflex humeral vein and posterior circumflex humeral vein.

The first part of the axillary vein receives the cephalic vein

The axillary vein therefore drains deoxygenated blood from the arm, axilla and superolateral chest wall.

Question 38

Superficial veins of the upper limb

Answer 38

The major superficial veins of the upper limb are the cephalic and basilic veins.

They are located within the subcutaneous tissue of the upper limb.

cephalic vein runs along the pre-axial border of the upper limb and the basilic vein runs along the post-axial border.

The basilic vein originates from the dorsal venous network of the hand and ascends the medial aspect of the upper limb. At the inferior border of the teres major, the basilic vein moves deep into the arm. Here, it combines with the paired brachial veins from the deep venous system to form the axillary vein.

The cephalic vein also arises from the dorsal venous network of the hand. It ascends the anterolateral aspect of the upper limb, passing anteriorly at the elbow. At the shoulder, the cephalic vein travels between the deltoid and pectoralis major muscles (in the deltopectoral groove), and enters the axilla via the clavipectoral (deltopectoral) triangle (here). Within the axilla, the cephalic vein drains into the first part of the axillary vein.