1. Cervical Anatomy and Biomechanics Flashcards
Vert Bodies Relationships
- Teeth (mouth closed) @ lvl of C2
- Thyroid cart @ lvl of C4/C5
Forces on C/S
- wt. of head (approx 8% of BW)
- contraction of surrounding mm’s
-
Loads:
- more load on IV Jts in FLEXION
- more load on Facets in EXTENSION
More load in IVJs in
FLEX
More load on Facets in
EXTENSION
Anatomy & biomechanics Lower C/S
C3-C7
Processes in Lower C/S
- SP tips from C2-C5 bifurcated (split) in 52% of c/s
- TPs
- foramen for vert. aa→ just ant. to spinal nerve
- “trough” for spinal nerve→ post to vert aa
- Mm attach’s → levator scap attaches to TP of C1-C4
Anatomy & biomechanics Lower C/S
C3-C7
Unciform (Uncinate Processes)
- SUP vert surface has a SUP directed projection that courses ANT and POST→ uncus or uncinate process
- INF portion of VB is beveled to allow articulation to articulate w/ the uncinate process of the vertebrae below
- debated in literature as to whether or not its a true synovial jt.
-
Limits lateral flex ROM @ C3-C7
- *provides Lat stability in C/S
Zygapophyseal Joints
Z-joint or facet joints
- Collectively make up “articular pillar”→ important palpation landmark
- Just post to trough-like TPs/spinal nerves
- Dome shaped
-
More HORIZ in SUP segments, and more VERT in LOWER segments
- *TIP: orients toward the eyes
Z-Jts of C/S
One more detail
Have meniscoid synovial folds→ May become entrapped
Movement Patterns LOWER C/S
Axis of Rotation
Axis of Rotation occurs in the plane of the facet joint
Movement Patterns LOWER C/S
Coupled Motion
Coupled Motion
Axial rotation is coupled w/ ipsilat lateral flexion
i.e. rotation and lateral flex couple to same side
Movement Patterns
ROM
ROM
- Avg of 8degs in ea direction for each segment for rotation→ (C2-C3 to C7-T1)
- Composite rotation motion for lower C/S of about 40degs ea direction
- Segmental cervical ROM for flex/ext varies sig’ly w/ time of day
-
*Motion in one plane will restrict mvmt in other planes
- Ex: if in flexion, rotation and L/F will be limtd as much of the jt surface gliding was “used up” to achieve flexion****
CS Intervertebral Discs:
Which segments and what about them?
- CS discs: C2-3; C3-4; C4-5; C5-6; C7-T1 (cervicothoracic junction)
- Morphologically diff from lumbar discs
CS Intervertebral Discs
How are they diff/characteristics
- Post annular wall of minimal thickness
- Reinforced posteriorly by PLL
- Reinforced laterally by uncinate process
- Crescent shaped when viewed from above→ thickest anteriorly, progressively thinning when traced to the uncinate processes
- Arranged in layers→ fibers in woven arrange.
- Posterior annulus consists of one lamina of vert. oriented collagen fibers ~1mm thick
C/S: Nucleus Pulposus
- Present @ birth and progressively less evident in adolescence
- Essentially absent by age 40→ the nucleus is a ligamentous fibrocartilaginous “dry” core that is consistency of soap w/ little or no proteos
Upper Cervical Region
Consists of ….
*Atlanto-Occipital joint (O-A joint)
*Atlanto-Axial joint (C1-C2)
*rememer Atlas (C1) is Atlas because it “holds the head on top”
The Atlas (C1)
“Holds the head”
- Acts essentially as a washer interposed bw head and C2
- few mm’s act directly on Atlas
- Concave SUPERIOR articular surfs articulate w/ Convex condyles of Occiput
- C1 (Atlas) does NOT have vert. body→ embryological vert. body of Atlas becomes DENS of Axis***
The Atlas (C1)
Movement Patterns: Atlanto-Occipital (O-A Joint)
-
Primary Motion→ Flex/Ext (“OA Nodding, little “sup nod”) @ this lvl)
- Avg ROM→ ~15degs
-
During L/F w/ head prevented from turning→ Reactive contralateral rotation of Atlas occurs
- Ex. L/F to LEFT, Atlas rotates to RIGHT
Atlanto-Axial Jt (C1-C2)
Stuff…
- Rotation @ Atlanto-Axial (C1-2) occurs as the anterior arch of the Atlas (C1) pivots around the odontoid process (DENS) of the Axis (C2)
- W/ Rotation→ Lateral mass of the ipsilateral Atlas must slide backward and the contralateral lateral mass must slide forward→ i.e. the Atlas “screws down” on the Axis as it rotates
Passive Support: Ligaments
Alar Ligament
- Runs obliquely from posterior lateral apex of dens to the medial occipital condyles
- Primary limiting structure to head rotation to the contralateral side
Passive Support: Ligaments
Transverse Band of Cruciform Ligament
(the one that makes it a “Cross”)
- Passes BEHIND DENS, anchoring DENS TO Atlas
- Primary source of stability of the Atlanto-Axial jt→ Prevents subluxation of C1 on C2***
Passive Support: Ligaments
Superior and Inferior Projections
- Attach TO occiput and base of the Axis respectively→ forms a Cross→ hence the name Cruciform Ligaments
Passive Supports: Ligaments
Ligamentum Flavum
The “Yellow Ligament”
“Yellow Ligament bw adjacent lamina”
Ligamentum, Lamina—- REMEMBER!!!
- Consists of elastin fibers→ yellow color
- Hypertrophies and begins to lose elasticity by 45yo
- Projections INTO vert. canal
- MAJOR contributor of central canal stenosis
Ligamentum Nuchae
*Consists of 2 parts
-
Dorsal raphe
- Firmly attached to external occipital protuberance and SP of C7
- Formed from interweaving of R and L upper traps, splenius capitis, rhomboid minor
-
Fascial Septum
- running from dorsal raphe to merge w/ interspinous ligs and A-A and O-A membranes
Implications of Ligamentum Nuchae
- Traps + Splenius capitis are NOT directly attached to the SP ABOVE C7
- In supporting the scapulae the trapezius acts transversely on the C7 and T1 SPs
- Upper trap fibers act entirely on the clavicle @ insertion, and nuchal line of the skull & dorsal raphe of nuchal ligament @ origin
Sinuvertebral Nerves
aka reason for pain from discs
- Branch of ventral (ant.) ramus of spinal nerves; Receives autonomic fibers from sympathetic trunk via gray ramus communicans
- Innervates dural theca, nerve root dural sheath, periosteum, epidural contents, spinal canal, and the IVD
- Transmits pain in rxn to inflammatory material produced by injured discs
