Cervical Spine Biomechanics Flashcards
most common cause neck pain
53% MVA
45% falls and sporting accidents
traumatic injury most common
typical vertebrae
3-6
atyptical vertebrae
1-2
craddle
C1
axis
C2
whats special about C3
rooted down into C4, not much mobility
joints 4-7 are considered what
the column
vertebrae are built for __ not __
mobility, stability
neutral zone
-across OA-AA complex
50% greater neutrality than rest of spinal column
-greater laxity to capsule and ligaments
muscular forces of upper cervical
- multifidus, interspinalis, semispinalis cervicis, capitis, etc
- put brakes on eccentrically, muscle strain may appear later on, after trauma
joint morphology
uncinate processes present of posterolateral superior and inferior surfaces
- joints of vonlushka=unconvertebral joints
- -glide/guide flexion and extension and limit side bending
- fracture of TP may severe vertebral artery
- facets
- SP
TPs are in what direction
- anterolateral
- lateral grooves
- predisposes TP to fx
- 1-4=lateral masses
- 5-7 are transverse processes
- ecclusion at C2 because vertebral artery leaves foramen
vertebral artery compromise
- skeletal m and fascial bands at or near transverse foramen of C6
- osteophytes adjacent to C4/C5 and C5/C6
- gliding motion at AA articulation
- -leasds to VA compromise
- -downsyndrome and RA more likely b/c increased laxity
- extension and rotation likely to ecclude blood flow
joint morphology: atlas
- also known as cradle
- no body, no SP, ring shaped
- 2deg no body, has lateral masses for wt bearing
- superior facets concave, accept the convex occipital condyles
- -arthrology: OA: plane, synovial joint
- -plane secondary to 3 DF of motion (20 flexion and ext, 5 SB, 1 rotation.
- inferior facets slightly convex, facet on internal surface of anterior arch
OA extension
20 degrees
-45 total extension, 20 comes from OA joint
OA flexion
20 deg
-20 of 45 comes from OA
OA sidebending arthrokinematics
5 deg
-right SB:
Right OA rolls inferomedially and left OA rolls superolaterally
OA rotation arthrokinematics
-right rotation
Left OA moves ant and sup, right OA moves post and sup
joint morphology: axis
- superior facets of lateral zygopophyseal jts are convex
- inferior facets are orientated 40 deg from transverse plane and face medial
cervical arthrology of AA
3 joint composition
- 1 median atlanto-axial joint: synovial, trochoid (privot)-dens/osteoligamentous ring
- 2 lateral facet joints: plane/synovial
- 40 deg initial rotation allotted at AA jt, other 45=summation of cervical vertebrae
- -60 rotation is standard, but more likely to see closer to 90
- zero flexion or extension allowed 2ndary lig restrictions=protection of brainstem from dens
AA rotation
40 deg
arthrokinematics of AA
-right rotation
anterior inferior for L facet, posterior inferior for R facet
C2/C3 junction
“the root”
-fryettes law applies here
fryettes law 1
at certain segments sidebending and rotation coupled to opposite sides
- ex=C2/C3. see pure sidebending osteokinematically, but arthrokinematically researchers say sidebending may be coupled with rotation internally b/c shape of joint
- occurs in neutral and nonneutral positions (sagittal plane movements, so neutral head position or flexion/ext)
fryettes law 2
side bending and rotation coupled to opposite sides
cervical morphology: typical vertebrae
“the column”
- C3-C7
- plane, synovial zygopophyseal joints
- meniscoid properties
- intervertebral disc
- synovial, planar, diarthrodial joints lined with hyaline cartilage surrounded by a capsule with meniscal inclusions
- impingement may result
- innervation to capsules via medial branches of cervical posterior rami C2-C8 and sinuvertebral nerve
- source of referred pain
clowards area
- irritation to joint capsule will refer down further
- insidious onset thoracic region pain, check cervical spine first
how far does C7 refer down
-down to T6/T7/inferior border scap
what’s unique about cervical discs
- lack concentric annulus, so the technical definition of a herniation cannot apply here.
- they have an “uncovertebral cleft” posteriorly, so disc slippage will not break through annulus fibrosus
- the disc is more fibrocartilagenous than jelly like, more sponge like. may not be as disc like as thoracic/lumbar
- NP comprises 25% of disc at birht, lumbar 50%
- characterized by fibrocartliage, with no gelatinous component as the person matures to adulthood
discogenic pain
-same concept. pain cannot arise from posterolateral fissures in annulus b/c there is none. likely source is strain/tears of anterior anulus fibrosus, and strain of lateral portions of posterior longitudinal lig by bulging disc
cervical kinematics: typical vertebrae
- fryettes law 2-occurs in neutral and non-neutral conditions
- osteokinematic flexion and extension
- osteokinematic rotation and sidebending
- how can we Sb left and rotate right in c. spine?=lower C-spine sidebends, AA rotates
vertebrae associated with each law
Fryettes law 1: C3/C4 and up
Fryettes law 2: C5-C7
flexion is a good movement for stenosis because..
-opening and gapping of joints in flexion of intervertebral foramen
lower cervical rotation/side bending arthrokinematics of facets joints
- R side bending/rotation
- -R facet goes post/inf
- -L facet goes ant/sup
direction of rotation is named by..
-anterior body of vertebrae
greatest motion in combined flexion and extension
-osteokinematically, the greatest motion occurs in the lower cervical vertebrae (C4/C5, C5/C6) while individually the most occurs in C0/C1
ligament reinforcements:transverse
transverse ligament or atlantal-axial cruciform ligament
- creates post and ant portions of atles (separates and keeps dens away from spinal cord)
- separating dens from spinal cord
- longitudinal fibers attach occiput to axis
ligament reinforcements: alar ligament
- paired ligaments-dens to med. occiput
- taut in flexion, lax in extension (2ndary action)
- limits rotation of H and N to opposite side
- help to prevent ant. displacement of C1 on C2
- late movement of C2 (greater than 20) during rotation may suggest alar left sprain
whiplash injuries
- body elevates from hips, compresses spine
- start to extend head with a MVA, head will move first in the direction that the force was applied
- 200 ms, body compressed and extended spine
- 300 ms, head flexes forward
C5/C6 IAR during whiplash
- normally constantly changes with glides/slides, on C6 vertebrae. Normal motion of C5 extension is posterior roll over C6 and inferior glide, but during whiplash it changes.
- IAR shifts up to C5 during whiplash, andgle shifts down, inf. component increases.
- there is a chiseling of inferior facet by superior facet of C5. bone bruise, fracture, AC insult. suggests delayed healing process
tissues insulted due to trauma
- vertebral endplate
- tension/compression forces
- disc bulge/protrusion/prolapse/sequestration
classification of disk herniation/insults
- disk protrusion (annular fibers intact)
a. localized annular bulge-usually laterally
b. diffuse annular bulge-usually post. - disk prolapse (annular fibers disrupted)
- nucleus has migrated through the inner laminar layers, still contained - disk extrusion (annular fibers disrupted)
- nucleus has broken through the outermost layer - disk sequestration (annular fibers disrupted)
- nucleus separate from disk/ now in spinal (vertebral) and/or intervertebral canal
innervation of annulus
- only outer 1/3 is innervated
- can have herniation through 2/3 and not know it
how does optimal posture affect forces on the neck
-minimalizes the forces acting on the neck. a forward head posture accentuates the forces acting on the musculature and structures in the neck
combined movement: protraction
-upper cervical extension, lower cervical flexion
combine movement: retraction
-upper cervical flexion, lower cervical extension
capital extensors
- Obliquus capitis superior
- rectus capitis posterior major+minor
obliquus capitis superior
-extends and SB ipsilateral
obliquus capitis inferior
-rotates atlas ipsilateral
rectus capitis minor
-extends and rotates ipsilateral
rectus capitis major
-extends and rotates ipsilateral
semispinalis
contralateral rotation, bilateral extension
splenius capitis/cervicis
ipsilateral side bending/rotation
bilateral=extension
guy wire effect
- supports and keeps neck in balance position/ neutral position
- levator scap posterior and scalenes anterior
- act like a guy wire on a pole, keep it straight up and balanced
- insufficiency will pull one way or another
longissimus capitis
bilaterally extends, ipsilaterally rotates
longissimus cervicis
extends, SB neck
semispinalis capitis
Bilaterally extends, ipsilaterally rotates
scalenes
bilaterally flex, ipsilaterally side bend and rotate
longus capitis/longus colli
flex head/flex neck respectively
what happens to the TMJ during forward head posture
-jaw depresses and goes into retrusion, leads to increased compression of joint, wear and tear
