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
Atlanto-Axial (C1-C2) Joint Rotation
Info…
- Atlanto-Axial C1-C2 joint rotation is 43degs +/- 5degs ea. direction
- Primarily limited by tension in the contralateral Alar Lig. (e.g. R. Alar lig limits L rotation)
- Some evidence BOTH alar ligs limit rot. in either directions
S/B Atlant-Axial Joint
UPPER C/S**
- SB of Atlanto-Axial Joint (C1-C2) involves BOTH a lateral translation of C1 IPSILATERALLY** And **rotation CONTRALATERALLY
- SB to LEFT→ LEFT translation of C1
- Accompanying this→ Right rotation (to opp side) of C1 that is due to the slop of facets
- Hence→ “In the Upper CS, rotation and LF are coupled in opposite directions”
- they are coupled same direction in LOWER C/S
- Hence→ “In the Upper CS, rotation and LF are coupled in opposite directions”
- Accompanying this→ Right rotation (to opp side) of C1 that is due to the slop of facets
- SB to LEFT→ LEFT translation of C1
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 Support: Ligaments
ALL (Ant Longitudinal Lig)
On Ant surfaces of bodies starting @ C2-C3; LIMITS EXT
- @ Occiput-C1 (OA)→ Atlanto-Occipital Membrane
- @ C1-C2 (A-A)→ Atlanto-Axial Membrane
Passive Support: Ligaments
PLL (Post Longitudinal Lig)
Covers floor of vertebral canal, along posterior surfs of VB’s
- ABOVE C2→ cont’s as Tectorial Membrane
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
Muscles of the C/S
Roles:
Mvmt/head righting/positioning of special senses; stabilization; proprioception (dense amt of mm spindles and GTOs)
Muscles of the C/S
Extensors
Superf→ Deep
REVIEW all O/I/I/A
- Traps→ upper fibers
- Splenius capitis
- Splenius cervicis
- Semispinalis & Spinalis capitis
- Semispinalis cervicis
- Longissimus capitis
- Longissimus cervicis
- ***SCM (POST fibers act on UPPER CS)→ when acting w/ longissimus capitis, spinalis capitis and semispinalis capitis
- Suboccipitals:
- Obliquus capitis superior
- Rectus capitis posterior major and minor
Muscles of the C/S
Flexors
Superf→ Deep
REVIEW all O/I/I/A
- ***SCM (ANT fibers acting on LOWER CS)→ when acting w/ longus capitis
- Anterior scalene
- Deep Cervical Flexors***→ important for re-training!!!
- Longus colli
- Longus capitis
Muscles of the C/S
ROTATORS
Superf→ Deep
REVIEW all O/I/I/A
- Upper traps→ rotates head to OPP side
- SCM→ rotates head to OPP side
- Splenius capitis→ rotates head to SAME side
- Levator Scapula→ rotates neck to SAME side
- Rectus capitis posterior major→ rotates head to SAME side
- **Obliquus capitis inferior→ rotates C1 (on C2) to SAME side
Muscles of the C/S
Lateral Flexors
**Contraction of muscles on 1 side causes IPSILATERAL lateral flexion
Superf→ Deep
REVIEW all O/I/I/A
- Upper traps
- SCM
- Splenius capitis
- Semispinalis capitis
- Longissimus capitis
- Longissimus cervicis
- Middle and Post scalenes
- **Suboccipitals (UPPER CS)
Nerve Roots
Gen. Info
-
8 pairs Cervical Nerves;
- C1 nerve sits ABOVE C1, and so on
- C8 nerve sits ABOVE T1
- Occupy ¼ to ⅓ of the IVF diameter
Nerve Roots
Potential Sources of Compression: 5
- Disc Herniation
- Facet Jt Hypertrophy*
- Uncinate process spurring*
- Foraminal Stenosis*
- Peri-articular fibrous tissue*
NOTE: 2-5 are MAIN sources of nerve root compression AFTER 40yo*****
More on Disc Herniations in C/S
- MOST common @ the C5-6 and C6-7 lvls
- In general→ nerve root involved is the “lower #” of disc lvl***
- Ex. C5-C6 herniation compresses C6 nerve root
- This trend is true for all CS nerve roots EXCEPT C-8 nerve root→ C-8 nerve root just ABOVE T1 (bw C7 and T1) and thus vulnerable w/ C7-T1 disc
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
Some Final Biomechanical Notes…
- FLEXION of CS→ INCs size (diameter) of vertebral canal, but also INCs dural tension
- EXTENSION of CS→ DECs size (diameter) of vertebral canal
Flexion of CS does what to diameter of vertebral canal?
INCs size, but also INCs dural tension
EXTENSION of CS does what to size of vertebral canal?
DECs
Clinical Quiz:
Which motion (FLEX vs EXT of CS) would likely be more problematic for pt w/ cervical myelopathy?
EXTENSION!
-
Cervical Myelopathy
- RED FLAG!
- Central cord compression that impacts SC
- Abnorm reflexes
- Numb/tingle in BOTH UE or LE
- Progressive in nature
- B/L
- Balance issues, weakness
- Most pts are surgical which prevents things from getting worse
There IS coordination b/w cervical and oral-facial mm’s
Examples?
- Chewing
- during chewing, your cranium would wobble around if it were not for coordinated postural and stabilizing contractions of CS mm’s
Effects of FHP
Typical to see Tension where and due to what
- typ to see tension due to INCd postural contraction activity in a stretched/elongated position in upper traps and lev scap
Effects of FHP
Typ to see “stretch weakness” where?
Stretch weakness in scapular retractors and depressors
Effects of FHP
Typ to see Tightness in where?
Suboccipitals and pec minor
possibly SCM
FHP INCs the _______ on the CS, thus what has to happen?
INCs flexion moment on CS, thus CS extensors have to work harder to maintain static equilib
In FHP, there is INCd loading on _______
INC loading on lower cervical facet joints
bc Lower CS stays in flexed position
