L8: The cervical and thoracic spine and the brachial plexus Flashcards
How many cervical vertebrae are there?
Seven
C1, C2 and C7 are atypical
C3-C6 are typical
Describe the anatomy of a typical cervical vertebrae?
VB–> small and broad from side to side
Large triangular vertebral foramen
Bifid spinuous process
Transverse foramen (foramen transversarium) in transverse process–> passage way for vertebral artery, vein and symphathetic plexus
Anterior tubercle
Posterior tuberlce
Groove for spinal nerve
Articular facets–> coronal plane at 45 degree to axial plane
Superior articular facets–> upwards and backwards
Inferior articular facets–> downwards and forwards
What is the structure of the C1 vertebrae?
Atlas
Anterior and posterior arch connected by two lateral masses –> vertebral arches
Widest of cervical vertebrae
No spinous process or vertebral body
Anterior arch occupies 20% of circumference of ring–> attachment of anterior longitudinal ligament
Posterior arch 40% of ring–> attachment ligament nuchae
Articular facets on lateral masses
Superior articular facets–> cup shaped articulate with occipital condyles
Inferior articular facets–> C2 vertebrae
Transverse process with transverse foramen in them
What are the names of the joints found between the skull and C1 and C1 and C2?
Atlanto-occipital joint–> permits nodding
–> 50% of flexion and extension of the head
Atlanto-axial joint–> 50% total rotation of head and neck
C2 –> provides pivot on which the atlas rotates
What is the anatomy of the C2 vertebrae?
Axis
Strongest cervical vertebrae
Rugged lateral mass and large spinous processes
Odontoid process aka dens or odontoid peg–> projects upwards from body
Held in place by transverse ligament of the atlas acts as a pivot joint
Transverse process with transverse foramen in
What are the ligaments associated with the axis (C2)?
Transverse ligament–> holds dens in place
Apical ligament–> Attaches between odontoid process and base of skull
What is excessive movement between the atlas and axis called?
Atlantoaxial instability
Can cause neurological damage
Describe the anatomy of the C7 vertebrae?
C7–> vertebra prominens
Longest spinous process–> not bifid
Foraman transversium are small–> only transmit accessory vertebral veins
In the cervical region where does the spinal nerve run?
Spinal groove
Across the superior aspect of the vertebral pedicle
Between the anterior and posterior tubercles of the transverse process
Spinal nerve–> posterior to vertebral artery
Vertebral artery ascends through the foramina transvrsaria in C1-6 with vertebral vein and sympathetic plexus
Compared to the thoracic and lumbar region how does the spinal nerve exit the cervical region?
Spinal nerve exits above vertebrae
Until C7/T1 junction where C8 nerve root is the exiting nerve root
Neural segments also more inline with vertebrae
Spinal nerve leave horizontally to pass through IV foramina
Clinical impact–> no traversing nerve root, exiting root compressed
What is the ligamentum nuchae?
Thickening of the supraspinous ligament
Extends from the external occipital protuberance of the skull and the medial nuchal line to the spinous process of C7
Anterior border–> fibrous lamina attaches to the posterior tubercle of atlas and spinous process of vertebrae
Continuous inferiorly with the supraspinous ligament
What are the roles of the ligamentum nuchae?
Maintain the secondary curvature of the cervical spine
Assist cerivical spine to support the weight of the head
Major attachment site for muscles of the neck and trunk
What is the anterior longitudinal ligament?
Anterior border of the vertebral body From tubercle of atlas to sacrum Continuous with periosteum of VB Loosely adhered to the IVD Function: prevent hyperextension of vertebral column
What is the posterior longitudinal ligament?
Posterior VB
Body of axis to sacral canal
Superior to axis –> tectorial membrane of the atlanto-axial joint
Prevents hyperflexion
Clinical relevance–> disc prolapse tends to occur lateral to this
What are the movements of the cervical spine?
One of most mobile segments of spine
50% of nodding flexion and extension at atlanto-occipital joint –> remainder takes place at cervical facet joints
50% rotation (shaking head)–> atlanto-axial joint –> remainder at facet joints
Permits 45 degrees of lateral flexion –> occurs at facet joints
Describe the anatomy of the thoracic vertebrae?
12 thoracic vertebrae
Medium sized heart shaped VB
Vertebral foramen small and circular
Prominent transverse process with transverse costal facets (articulation with ribs)
Demi facets T2-T8 and whole facets T9-T10 on VB for articulation with head of ribs
T11-T12–> whole facets on pedicle
Long, spinous process, angulated inferiorly
Articular facets angulated at 20 degrees to coronal plane, 60 degrees to axial (transverse) plane–> superior face posterolaterally, inferior face anteromedially–> permits lateral flexion and rotation but prevents flexion and extension
What do the ribs attach to?
T1-T12
–>T2-8 demi facets on side of VB, superior and inferior demi facets for articulation with rib of same number and the rib below
–>T9-10 whole facets on VB
–>T11-12 facets on pedicle
Rib 1-7 curve round insert onto sternum via costal cartilgae
Ribs 8-10 insert onto costal cartilage of superior rib
Ribs 11-12 –> no anterior attachment, terminate in abdominal musculature
Head of rib articulates with a costal facet–> cartilage lined depressions
What does the thoracic spine, ribs and sternum do?
Provide stability and protection for the heart, lungs, liver and other organs
Ribs connected to T11-12–> protection of retroperitoneal kidneys
Which of the thoracic vertebrae are atypical and posses whole facets?
T1: superior facet is whole, articulates with head of rib 1, inferior costal facet is demi
T9 and 10: whole costal facets, extend from head of VB to pedicule
T11 and 12: whole costal facets located on pedicule
What changes occur to the spinous process as you go down the thoracic spine?
Becomes shorter and less oblique from T1-T12
T12 spinous process more similar to lumbar vertebrae
What does the tubercle of the rib articulate with?
Costal demi facet on transverse process
What angle are the facets joints at? How does this affect the movement of the thoracic spine?
60 degrees to transverse plane
20 degrees to coronal plane
Superior articular facets face posterolaterally
Inferior articular facets face anteromedially
Permit lateral flexion and rotation
Limits Flexion and extension
Describe the anatomy of the lumbar vertebrae?
Large, kidney, shaped vertebral body Triangular shaped vertebral canal Large blunt transverse processes Short blunt spinous processes Facet 90 degress to transverse plane, 45 degress to coronal plane Superior face posteromedially Inferior anterolaterally Large range of flexion and extension, small amount of rotation and lateral flexion
What is the brachial plexus?
Union of anterior rami of C5-T1 spinal nerves
Commences in the neck and terminates in the axilla
(Posterior rami–> skin and musculature of intrinsic back muscles)
What are the different parts of the brachial plexus?
Roots, trunks, divisions, cords and branches
What forms the roots of the brachial plexus? Where does it pass?
Roots formed by the anterior rami of C5-T1
Pass between the scalenus anterior and scalenus medius–> enter posterior triangle of the neck
What are the trunks made up of?
Three trunks
Convergence of the roots
Named after relative anatomical locations
Superior trunk: C5 and C6
Middle trunk: C7
Inferior trunk: C8 and T1
Travel inferolaterally across the posterior triangle of neck
What are the division of the brachail plexus?
Trunks divide in posterior triangle
Anterior division and posterior division
Divisions leave posterior triangle and enter axilla - behind clavicle
Anterior supplies flexor, posterior supply extensors)
What are the cords?
In axilla, division recombine to form the cords
Name according to position relative to axillary artery
Lateral cord: union of anterior division of superior and middle trunk
Posterior cord: union of posterior division of superior, middle and inferior trunks
Medial cord: continuation of anterior division of inferior trunk
What are the branches of the brachial plexus?
5 major terminal branches Supply entire compartment of upper limb Musculocutaneous nerve C5,6,7 Axillary C5, 6 Median C6, 7, 8, T1 Radial C5, 6, 7, 8, T1 Ulnar C8, T1
Which nerves come off before the branches of the brachial plexus?
Long thoracic nerve (C5-7 directly from anterior rami (roots))
Medial pectoral nerve (C8-T1 from medial cord)
Lateral pectoral nerve (C5-7 from lateral cord)
Upper subscapular nerve
Thoracodorsal nerve
Lower subscapular nerve
–> All three of posterior cord
What are 6 key points about the brachial plexus
- Each muscle supplied by more than one spinal cord segment
- More distal muscles supplied by inferior cord segments
- Divergence of fibres in plexus as both flexors and extensors are supplied
- Needs to be re-assortment of nerve fibres
- Number of spinal nerves contributing to the terminal branch is roughly the same as the number of joints it supplied
- Sensory innervation to the limb bud follows loop like pattern
What can you look for in the cadaver when dissecting to help get your bearings?
M shape
Made from Musculocutaneous, median and ulnar nerves
Lie superficial to the axillary artery
What happens if you injury the brachial plexus?
Affect motor function and cutaneous sensation
Traction injuries affect upper or lower nerve roots of brachial plexus
What happens if you get an upper brachial plexus injury?
Result from excessive increase in angle between neck and shoulder
Result of trauma or during child birth if baby’s head is pulled and the shoulders are stuck
C5 and C6 damaged
C5- shoulder abduction and external rotation affected
C6- elbow flexion, wrist extension and supination affected
Which muscles are affected by an upper brachial plexus injury?
Deltoid (axillary nerve C5 and 6) Teres minor (axillary nerve) Biceps Brachii (musculocutaneous C5-7) Brachioradialis (radial nerve C5-T1) Brachialis (musculocutaneous C5-7) Coracobrachialis (musculocutaneous C5-7)
What is the clinical presentation of a upper brachial plexus injury?
Erb's palsy Arms hang by side Internally (medially) rotated Adducted arm Extended elbow Wrist flexed Waiters tip position
What happens with lower brachial plexus injury?
Forced hyperextension or hyperabduction
Childbirth- traction injury if arms are delivered first and used to pull baby out
Klumpke’s palsy
Nerve roots C8 and T1 affected
C8: finger flexion/ finger extension
T1: Finger abduction and finger adduction
What muscles are affected in an lower brachial plexus injury?
Intrinsic muscles of the hand
Flexor carpi ulnaris, and ulnar half of flexor digitorium profundus
Also muscles supplied by C8 and T1 fibres of medial and radial nerves
What is the classical clinical presentation of a lower brachial plexus injury?
Claw hand
Hyperextension of the metacarpalphalangeal joints
Flexion of interphalangeal joints
Abduciton of the thumb and wasting of interossei
Where is the pectoral region?
Anterior chest wall
What are the muscles of the pectorial region?
Pectoralis Major Pectoralis Minor Serratus Anterior Coracobrachialis (not really chest wall but important landmark) Subclavis Deltoid