biomechanics of the cervical spine. ppt (3)
TRANSCRIPT
Biomechanics of Cervical Spine
Biomechanics of Cervical Spine
Presented By-Debanjan Mondal
MPT(Musculoskeletal), BPT, CMT,
Ergonomist.
Made up of two anatomically and
functionally distinct segments.
1.Superior segment/suboccipital
segment-
-consist of c1 /atlas and c2/axis
-connected to eachother and
occiput with complex chain of joints.
-having 3 axes and 3 degrees of
freedom.
2.Inferior segment-
-streching from inferior surface
of axis to the superior surface of
T1.
-In total there are 7 cervical
vertebras-
c1-c2 c3-c6
c7
atypical typical
Structure of a typical cervical
vertebra
Vertebral body-superior plateau
is raised on either sides by 2
buttresses.
which is called as unciform process.
It is concave transversely and
convex anteroposteriorly-resembling
a saddle .
Unciform processes guoides the AP
movements during flexion and
extension ut limits lateral flexion
Pedicals-connects the vertebral body to the transverse process.
Project posterolaterally.Lamina-part of the posterior archMeets in the midline to form the
bifid spinous processProjects posteromedially and are
thin and slightly curved.
Spinous process-short slender and
extend horizontally
The tip is bifurcated
Face superiorly and medially
The length of spinous process
decreases from c2-c3
C3-c5 remains constant
And undergoes a significant increase
at c7.
Vertebral foramen –is large and
triangular
Transverse process
They are peculiar in
orientation
They are hollowed in to
a gutter AP and they
point AL.
The posteromedial end
of the gutter lines the
intervertebral foramen.
The AL end is bifid
giving attachment to
Articular processes-they bear
superior and inferior articular facets.
Superior facets face superiorly and
medially
Inferior facets face anteriorly and
laterally
Structure of a atypical cervical vertebra
Atlas /c1-its ring shaped
Transverse diameter greater than AP
diameter
Has two lateral faces oval in shape
running obliquely anteriorly and
medially
Which bear biconcave superior
articulate facet superiorly and medially
meant to articulate with occipital
condyles
Inferior articular facet –facing
inferiorly and medially
Convex AP
Corresponds to superior facet of axis
Anterior arch consist of small
cartilagenous oval shaped articular
facets for the odontoid process of axis
Posterior arch is initially flattened but
becomes thicker posteriorly to form
posterior tubercle on the midline.
Transeverse process
No spinous process
No intervertebral disc
The axis-is atypicsl
Superior surface of the body carries
centrally the odomtoid process which
acts as a pivot for atlantoodontoid
joint .
Laterally possess 2 articular facets
facing superior and laterally
Facets are convex AP and flat
transversely
Posterior arch consist of narrow
laminae
The cartilage lined inferior articular
The cartilage lined inferior articular
process corresponds to the superior
articular process of c3
Transverse process
The atlanto-axial joint complex
it is a plane synovial joint
comprises of 3 mechanically linked
joints
The central joint is the atlanto
odontoid joint
Two lateral joints-atlanto axial joint
Atlantoodointoid joint
it is synovial trochoid /pivot joint
Jointsurfaces-anterior articular facet
of odontoid and posterior articular
facet of the anterior arch of the
atlas
Movements at atlantoaxial and
atlanto
odontoid joint
Flexion-point of contact b/w two
convex surface moves forward
interspace of atlanto odontoid joint
opens superiorly
Extention
Interspace of atlanto odontoid
jointopens inferiorly
Radiological findingas does not shoe
opening of interspaces
This is due to transverse ligament and
keeps the anterior arch and odontoid
process in close contact
During flxn and extn tha inferior
surface of atlas rols and sides over
superior articular surface of axis
rotation
Left to right rotation-
The left lateral mass of
the atlas moves forward
Right lateral mass
recedes in rotation from
left to right and vice
versa from right to left
Movement of atlanto occipital joint
Formed b/w superior articular
facets of atlas and the occipital
condyles.
It is an enarthodrial kind of joint
Gives 3 degrees of freedom
Axial rotation-about vertical axis
Flexion/extension-about
transverse axis
Lateral flexion-about AP axis.
flexion
The occipital condylesrecede on the lateral masses of the atlas.
The occipital bone moves away from the posterior archof the atlas
Limited by tension developed in the articular capsules and the ligament
extension
Occipital condyles
slides anteriorly on the
lateral masses of the
atlas.
Occipital bone moves
neatrer to the posterior
arch of the atlas
Posterior arch of the
atlas and axis are
approximated
Limited by those 3
Lateral flexion
Movement only occurs b/w c0-c1
and c2-c3
Left lateral flexion-slipping of
occipital condyles on right of atlas
Right lateral flexion-vice versa
Ther is asmall range of motion
Total ROM-C0-C3=8 degrees
C0-C1=3 degrees,C2-C3=5
degrees
rotation
When occiput rotates on atlas its
rotation is secondary to rotation of
atlas on axis
Around vertical axis passing
through the centre of odontoid
Causes right anterior displacement
of oright occipital condyle on right
lateral mass of the atlas
Lateral atlanto occipoital ligamenr is
streched
Thus rotation of occiput to left is
associated with –
Linear displacement of 2-3 mm to the
left
Lateral flexion to the right
Movements at the lower cervical
vertebral column
Extension-ovrlyingvertebral body tilts and slides posteriorly
IV space is compressed posteriorly and opened wide anteriorly
Nucleus palposus is driven slightly anteriorly
Anterior fibers of annulus fibrosus is streched
Superiorly articulating facet slides
inferiorly posteriorly and tilts posteriorly
Limited by anterior longitudinal ligament
and by the impact of the posterior
arches through ligaments
Flexion-upper vertebral body tilts and
slides anteriorly
Intervertebral space is compressed
anteriorly and opened wide posteriorly
Nucleus pulposus is driven posteriorly
Posterior fibres of
annulus fiberosus is
streched
Limited by the tension
developed in the
posterior longitudinal
ligament
By the capsular
ligament,ligamentum
flavum,ligamentum
Combined lateral flexion and
rotation-
Does not occur as pure motions
Governed by orientation of articular
facets which are oblique inferiorly and
posteriorly
Rotation is always coupeled with lateral
flexion
Considering the whole cervical column
from C2-T1 extension component is
also added to these movements
Where as any movement b/w C6-C7
also adds up extension component
Thus three composite movement occurs
in 3 planes-
Lateral flexion –frontal plane
Extension-sagittal plane
Rotation-transverse plane
RANGE OF MOTIONJOINT COMBINED FLEXION ONE SIDE ONE SIDE
EXTENSION LAT BENDING AXIAL ROTATION
C2-C3 10 10 3
C3-C4 15 11 7
C4-C5 20 11 7
C5-C6 20 8 7
C6-C7 17 7 6
C7-T1 9 4 2
FROM- WHITE AND PUNJABI
stability
Cervical region bears less weoight
and are more mobile
Stability is provided by bony
configuration,muscles,ligamants
Muscles-flexion of head and
neck-
Depends on anterior muscles of the
neck
They are rectus capitis major, rectus
capitis minor
Longus cervicis which plays an
important role in straightening the cervical
column and holding it rigid
Scalene anterior posterior and medius
Suprahyoid and infrahyoid muscles
helps in supporting the cervical column at
rest
Thry are located at a distance from
cervical column
Thus acts via long arm of lever and are
powerful flexors of head and cervical
Extension of head and neck-
Brought about by posterior neck
muscles
They are0-splenius
cervicis,semispinalis
cervicis,leavator
scapulae,transverso
spinalis,longismus
capiis,spenius capitis,trapezius
These muscles helps in
maintaining the cervical lordosis
When contract unilaterally they
produce extension rotation and lateral
flexion on the same side
Both flexors and extensor group of
muscles are responsible to maintain
cervical column rigid in neutral
position
Essential in balancing the head and in
supporting weights carried on head
ligaments
Anterior atlnatoaxial
ligament,posterior atlantoaxial
ligament,tectorial
membrane,ligamentum nuchae
Transverse atlantal ligament-21.9
mm in length
Also refered as atlantal cruciform
ligament
Holds dense in closed
approximation against the anterior
Also serves as an articular surface for dense
Prevents anterior displacement of C1 on C2
Alar ligaments-arise from axis on either side of dens
Approx.1cm in legth
Are taut in flexion
Axial rotation of head and neck tightens both alar ligaments
Prevents distraction of C1 on C2
Apical ligaments-of the dens
connects the axis and occioital bone
of the skull
Biomechanics of cervical injuryWHIPLASH INJURY IS DUE TO HIT FROM
BEHIND CAUSING 1ST FORCED EXTENSION OF THE NECK FOLLOWED BY FOCED FLEXION OF THE NECK.
-2 PHAGES:
1)HYPEREXTENSION OF C5-C6 AND MILD FLEXION AT C0-C4
2)HYPEREXTENSION OF THE ENTIRE SPINE
-IF THE HEAD IS IN SLIGHT ROTATION THEN BEFORE EXTENSION IS FORCED TO FURTHER ROTATION CAUSING INJURY TO FACET JT CAPSULE, I.V DISC AND ALLAR
LOWER CERVICAL FACET RESPOND WITH SHEAR AND DISTRACTION MECHANISM IN FRONT AND SHEAR AND COMPRESSION IN THE BACK.
DUE TO THE INJURY CAUSE CHANGE IN PIVOT POINT AT C5-C6 CAUSING JAMMING OF THE INFERIOR FACET OF C5 AND SUPERIOR FACET OF C6
C2-C3 FACET IS THE COMMON SITE FOR THE PATIENTS WITH HEADACHE(60%) AND C5-C6 IS THE SITE FOR REFFERED ARM PAIN
Facet joint syndrome FACET JOINT IS A SYNOVIAL JOINT AND
BETWEEN TWO FACET JOINT CARTILAGENOUS DISC IS PRESENT, DURING FACET LOCKING SYNOVIAL MEMBRAME AND THE DISC GETS ENTRAPPED BETWEEN TWO FACET BONES.
PAIN IN SIDE FLEXION AND ROTATION TO THE SAME SIDE AND EXTENSION AS WELL.
COUPLING OF LATERAL FLEXION TO ROTATION IS ALTERED DUE TO FACET SYNDROME.
- CERVICAL SPONDYLOSIS BEGINS WITH CAPSULAR --RESTRICTION OF THE FACET JOINTS WITHOUT BONY -CHANGES AND GRADUALLY PROGRESS TO CHARACTERISTIC FLATTENING,LIPPING AND SPURRING OF THE VERTEBRAL BODY.
- ACCELERATED BY INJURY
- BONY STENOSIS OF INTERVERTEBRAL FORAMEN IS POSSIBLE.
- LOWER CERVICAL SPINE WILL BE KYPHOTIC
- ACTIVE ROTATION, LATERAL FLEXION TO PAINFUL SIDE WILL BE RESTRICTED WITH EXTENSION AS WELL.
- CAPSULAR RESTRICTION IN LOWER CERVICAL AREA
- MOBILITY IN UPPER CERVICAL AREA IS
GENERALLY QUITE GOOD.
- OSTEOPHYTES STABILIZES THE
VERTEBRAL BODY ADJACENT TO THE
DEGENERATIVE DISC AND INCREASE
THE WT. BEARING SURFACE OF
VERTEBRAL END PLATES.
- CERVICAL MYELOGRAM SHOWS
SPONDYLOTIC CHANGE WITH
OSTEOPHYTIC CHANGE
Acute cervical injuries
The most common fracture mechanism in
cervical injuries is hyperflexion.
Anterior subluxation occurs when the
posterior ligaments rupture.
Since the anterior and middle columns remain
intact, this fracture is stable.
Simple wedge fracture is the result of a pure
flexion injury. The posterior ligaments remain
intact. Anterior wedging of 3mm or more
suggests fracture. Increased concavity along
with increased density due to bony impaction.
Usualy involves the upper endplate.
Unstable wedge fracture is an unstable flexion injury due to damage to both the anterior column (anterior wedge fracture) as the posterior column (interspinous ligament).
Unilateral interfacet dislocation is due to both flexion and rotation.
Bilateral interfacet dislocation is the result of extreme flexion. BID is unstable and is associated with a high incidence of cord damage.
Flexion teardrop farcture is the result of extreme flexion with axial loading. It is unstable and is associated with a high incidence of cord damage.
Extension injuries
Hangman's fracture
Traumatic spondylolisthesis of C2.
Extension teardrop fracture
Hyperextension in preexisting spondylosis
'Open mouth fracture'
Axial compression injuries
Jefferson fracture is a burst fracture of the ring of
C1 with lateral displacement of both articular masses
.
Burst fracture at lower cervical level
Thank you.Debanjan Mondal