(2) Cervical Spine Functional Anatomy / Biomechanics Flashcards
Purpose of Vertebral Column
Stability allowing full mobility
Protect SC and axial neural tissues
Curves within Vertebral Column allow ___.
increased flexibility
shock-absorbing capabilities (flattening of any curve decreases shock-absorbing capability)
Anterior Vertebral Column
Vertebral Bodies
IVDs
Hydraulic and WB portion provides shock absorption
Posterior Vertebral Column
Articular Processes
Zygapophyseal (Facet) Joints
Provides gliding mechanism for movement
Joints Within Each Spinal Segment
Anterior: 2 Vertebral Bodies / IVD
Posterior: Articulations between superior articular processes of inferior vertebra and inferior articular processes of superior vertebra
Horizontal vs. Vertical Articular Surfaces
Horizontal favor axial rotation
Vertical (sagittal / frontal) block axial rotation
C-spine falls in between (mostly horizontal)
How does the position of the C-Spine change as you move down each level?
Starts mostly horizontal / moves toward 45 degrees in lower segments
When looking at the spine, where does the line of gravity fall?
On the concave side of each of the 3 curves
The amount of available spinal motion is affected by ___.
Disc-vertebral height ratio
Compliance of fibrocartilage
Dimensions / shape of adjacent vertebral end plates
Age / Disease / Gender
The type of spinal motion available is governed by ___.
Shape / orientation of articulations
Ligaments / muscles of segment
Size / location of segment’s articulating processes
What is the largest avascular structure in the body?
IVD
Parts of IVD
NP
AF
End Plate
Cervical / Lumbar IVDs vs. Thoracic IVDs
Cervical / Lumbar IVDs thicker in anterior portion (creating Lordosis)
Thoracic IVDs uniform in thickness
Does the IVD have the ability to move by itself?
No!
What 5 major stresses does the IVD resist?
Axial Compression
Shearing
Bending
Twisting
Combined motion
Which combined motion is a common MOI for disc herniations?
Bending and twisting
Spinal Junctions
Common areas for symptoms / pathologies
Craniovertebral (CV): Atlas / Axis / head
CT: Mobile lower c-spine meets stiffer upper t-spine
TL: Between t-spine (large ability to rotate) and l-spine (limited rotation abilities)
LS: Mobile l-spine meets relatively stiff SI joints
Mechanical (Static) Stability
State of equilibrium when body is still
Controlled (Dynamic) Stability
Passive System: Ability to resist forces of translation / compression / torsion (especially at end ranges)
Active System: Muscles must be coordinated within hierarchy of interdependent levels to control body relative to environment
If passive system is damaged, active picks up the slack (structures fatigue more quickly)
CNS: Feedforward / feedback control to augment stiffness
*Insufficiency results in active and passive systems working harder to maintain control (fatigue faster)
What two components contribute to Spinal Stability?
Local mobility
Global stability
How is spinal stability taxed / tested?
Through perturbations
Injuries in Upper Cervical Spine can involve / result in:
Involve brain / brainstem / SC
Can result in death / HAs / vertigo / cognitive and sympathetic system dysfunction (poorer prognoses and more lengthy recoveries)
Foramen Magnum (C0)
Alar Ligaments attach to anterior surface
Brainstem / SC junction housed posteriorly
Occipital Condyles
Atlas (C1)
Ring-like structure
Transverse Ligament attaches here
Does NOT have a SP (CV extension > CV flexion)
Occipito-Atlantal (OA) Joint
Articulation between C0 and C1
ONLY vertebral level where convex condyles move on concave facet of Atlas (contralateral coupling of roll and glide)
Axis (C2)
Extends far posteriorly due to long SP
Odontoid Process (Dens): Extends superiorly until just above C1 / susceptible to fracture / Transverse Ligament passes along posterior surface
Atlanto-Axial (AA) Joint
Articulation between C1 and C2
ROTATION is main function
Transverse Ligament
Stretches between lateral masses of C1 / connects C1 with dens of C2
Counteracts anterior translation of C1 on C2 (particularly during cervical flexion) - excessive translation in this case could cause dens to compress SC / epipharynx / vertebral artery / superior cervical ganglion
Alar Ligaments
Connect postero-lateral aspect of Dens to medial surface of Occipital Condyles and lateral masses on C1
Main passive restraint to contralateral axial rotation and SB in CV region
Anterior OA Membrane
Connects upper border of Atlas to Foramen Magnum
Posterior OA Membrane
Attaches posterior arch of Atlas (C1) to posterior margin of Foramen Magnum
Tectorial Membrane
Arises from posterior Axis and eventually becomes continuous with Dura Mater
Anterior Suboccipital Muscles
Rectus Capitis Anterior
Rectus Capitis Lateralis
Posterior Suboccipital Muscles
Rectus Capitis Posterior Major
Rectus Capitis Posterior Minor
Obliquus Capitis Inferior
Obliquus Capitis Superior
Cranio-Vertebral Nerve Supply
Posterior (Dorsal) Ramus of C1 - follows vertebral artery
Posterior (Dorsal) Ramus of C2 - easily compressed between C1 and C2 during c-spine extension (making the movement painful) / AKA Greater Occipital Nerve
What areas of the Cervical Spine are implicated as primary causes of Cervicogenic HAs?
OA / AA / C2 spinal nerve
Cranio-Vertebral Blood Supply
Cervical Spinal Cord supplied by 2 arterial systems: central / peripheral
Anterior Spinal Artery supplies central and parts of peripheral systems - makes unilateral spinal cord infarctions rare
Upper Cervical Spine is responsible for ___% of ROM throughout cervical region.
~50
Which 2 articulations permit pure axial rotation?
AA Joint (C1 / C2)
T-L Junction (T12 / L1)
OA Joint Biomechanics
Deep sockets on C1 + no IV disc means increased bony congruency (stability)
Joint design encourages flexion / extension and impedes other movements
___% of total cervical rotation occurs at AA Joint.
60
___ nature of AA Joint means ___ motions occur between lower C-Spine and Atlas.
Biconvex, opposite
Lower C-Spine flexion w/ Upper C-Spine extension
Upper C-Spine flexion ___ space between Atlas (C1) and Dens (C2).
increases
Excessive gapping (instability) at C1/C2 can lead to what? In what populations do we often see this occur?
SC compression
Increased age / history of trauma / severe ligamentous laxity (RA) / cancer / down syndrome / malformation of Dens
Where are the SPs in relation to the TPs in the Cervical Spine?
Bifid SPs at same level as TPs
Uncovertebral Joints / Facet Joints
Uncinate processes on supero-lateral portion of VBs - Uncovertebral Joints limit SB and stabilize IVDs
Facet Joints at 45 degrees from frontal plane - allows rotation
Cervical IV discs are named for the vertebra ___.
above
C4 disc sits between C4 and C5
Progression of NP
NP rapidly fibroses (by 3rd decade of life is fibrocartilaginous)
Most >40 y/o’s have evidence of cervical disc degeneration
In Degenerative Disc Disease (DDD), ___ disc height results in ___ load.
decreased, increased
Cervical Foramina vs. Vertebral Canal
Foramina house 8 spinal nerve root pairs / large nerve roots nearly fill diameter / susceptible to compression in the case of uncovertebral osteophytes, extension and ipsilateral SB motions
Vertebral Canal houses 8 spinal cord segments / narrow space between SC and bony walls / susceptible to compression in the case of disc herniation secondary to AF being thin and weak posteriorly
Small changes in either space result in significant compression of spinal nerve roots or SC
Cervical Ligaments
Anterior Longitudinal Ligament (ALL)
Posterior Longitudinal Ligament (PLL)
Ligamentum Nuchae
Interspinous Ligaments
Ligamentum Flavum
Muscles that Affect Cervical Spine (Deepest)
Cervical Flexors:
Longus Capitis / Longus Colli
Rectus Capitis Anterior / Lateralis
Muscles that Affect Cervical Spine (Intermediate Depth)
Splenius Capitis / Cervicis
Semispinalis Capitis / Cervicis
Erector Spinae
Muscles that Affect Cervical Spine (Superficial)
Trapezius
SCM
Levator Scapulae
Rhomboids
Scalenes
Cervical Nerve Referral Patterns
C1-3: Head and neck pain
C4-8: Shoulder / anterior chest / UE / scapula
The Vertebral Artery is most vulnerable to compression / stretching at ___. What are the implications of this?
C1 / 2
This is why we rotate the neck in the VBI Screen completed during the series of 3 cervical clearing tests
Common Carotid bifurcates near ___. This artery senses changes in what?
mid to upper c-spine level (Internal / External)
Carotid Artery structures sense changes in O2 and CO2 levels / BP
C2-C7 Flexion / Extension (Facet Movement)
Flexion: Facets move up and forward
Extension: Facets move down and back
C2-C7 R SB / R Rotation (Facet Movement)
R SB: R facet moves down and back / L facet moves up and forward
R Rotation: R facet moves down and back / L facet moves up and forward
Rotation is ___ coupled with SB.
ALWAYS
Does not occur in isolation
SB and Rotation coupling more consistent in lower c-spine (same side, L rotation occurs w/ L SB)
Closing Restriction in Cervical Spine
Restriction of extension / R side bending / R rotation (same side of pain)
Opening Restriction in Cervical Spine
Restriction of flexion / L side bending / L rotation (opposite side of pain)
