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