8 - Craniovertebral jts & disarticulation Flashcards
Dens =
odontoid process
What are the characteristics of these “special” vertebrae, C1 & C2?
Atlas (C1)
Supports the skull
No body
No spinous process
Anterior arch & Posterior arch
Large lateral masses support the occipital condyles of the skull superiorly and articulate with the axis inferiorly
Foramen transversarium located in the large transverse process
Axis (C2)
Dens (Odontoid process) located on the body’s superior surface
Foramen transversarium located in the small transverse process
Spinous process is large and bifid
Craniovertebral Joints- Atlanto-occipital joint
=
Contributes to nodding movement (“Yes”)
Allow for tilting of the head, side-to-side
Craniovertebral Joints- Atlanto-axial joint
Contributes to rotation movement (“No”)
Both craniovertebral joints are synovial joints with no
discs
Atlantoaxial
Anterior arch of C1 & dens of C2
Synovial, pivot joint
ROM: rotation (supplies 50% of cervical rotation
Atlanto-occipital
Occipital condyles & superior facets of C1
Synovial, condyloid joint
ROM: flexion/extension
Dura Mater & Tectorial Membrane
Cranial vault is lined with periosteal dura mater
Continuous inferiorly into spinal column
Beneath this is the tectorial membrane
A superior extension of the posterior longitudinal ligament
Beneath the tectorial membrane are the
craniovertebral joints and deep ligaments
Remember that the dura is continuous inferiorly
along the length of the spinal cord.
Tectorial Membrane is superficial to the
dura mater
A & P Longitudinal Ligaments is superficial to the
dura mater
Anterior Atlanto-occipital Membrane is the superior extension of the
Anterior Longitudinal ligament
Anterior Atlanto-occipital Membrane attaches to
base of occipital bone superiorly at margin of foramen magnum
Anterior atlanto-occipital membrane Covers
anterior arch of atlas inferiorly
Extends from anterior margin of foramen magnum to cover the
anterior arch of C1 – the atlas
Posterior Atlanto-occipital Membrane
Posterior membrane between atlas & occipital bone
Posterior Atlanto-occipital Membrane
Uppermost extent of ligamentum flavum
Fills in gaps between posterior vertebral arches
These form part of posterior wall of vertebral canal
Ligamentum Flava Fills in gaps between
posterior vertebral arches
Deep Ligaments
Transverse ligament of the atlas
Cruciform (cruciate) ligament of the atlas
Alar (check) ligaments
Apical ligament of the dens (apical dental)
Transverse Ligament of Atlas - holds
dens of axis (C2) tightly to anterior arch of atlas (C1)
Very strong, bow-shaped ligament
fractures of the dens usually occur at its
base and often these fractures do not reunite due to the position of the transverse ligament
Cruciform (Cruciate) Ligament - Formed by
transverse ligament of atlas & 2 bands
Superior longitudinal band – attaches to
Cruciform ligament
foramen magnum base
Cruciform ligament - Inferior longitudinal band –
attaches to dens of C2 post.
Both bands (Crura) vertically
oriented. Thus, all 3 form a crucifix (cross)
Alar (Check) Ligament - extends from
Strong paired ligaments
Extends from dens to medial portions of occipital condyles
Alar check ligament - checks
lateral rotation of skull/head
Alar check ligament - strong
Strong paired ligaments nearly as thick as a pencil
Apical Ligament of Dens
Slender band ascending from apex of dens
Apical ligament of dens attaches to
anterior margin of foramen magnum
Apical ligament of dens Located deep to
superior longitudinal band of cruciform ligament
Neurovascular Structures-
Internal jugular v. – Internal carotid a. – Sympathetic trunk – CN VII – CNs IX, X, XI – CN XII –
IJV
emerges from jugular foramen
Internal carotid a. –
enters carotid canal
Sympathetic trunk –
gives rise to internal carotid plexus
CN VII –
emerges from stylomastoid foramen
CNs IX, X, XI –
emerge from jugular foramen
CN XII –
emerges from hypoglossal canal
Pharynx – hangs from
pharyngeal tubercle
Carotid sheath – located
lateral & posterolateral to pharynx