2. Biomechanics of Cervical Spine
Made up of two anatomically and functionally
distinct segments.
1. Superior segment/suboccipital segment:-
A -consist of c1 /atlas and c2/axis
B -connected to eachother and occiput with complex
chain of joints.
C -having 3 axes and 3 degrees of freedom.
2. Inferior segment-
A -stretching from inferior surface of axis to the
superior surface of T1.
B -In total there are 7 cervical vertebras-
c1-c2 c3-c6 c7
atypical typical transitional
Structure of a atypical cervical vertebra
1- 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
3. 2- The axis /C2-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
process corresponds to the superior
articular process of c3
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
Atlanto-odointoid 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- point of contact b/w two convex surface moves
backward
Interspace of atlanto odontoid jointopens inferiorly
Radiological findingas does not shoe opening of interspaces
4. 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 condyles recede 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 bony pieces
Flexion/extension-15 degrees
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 motionTotal ROM-C0-C3=8 degrees
C0-C1=3 degrees,C2-C3=5 degrees
5. 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
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 arch
Meets in the midline to form the bifid spinous process
Projects 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 scalene muscles.
Possess foramen transversarium
6. Articular processes-they bear superior and inferior articular
facets.
Superior facets face superiorly and medially
Inferior facets face anteriorly and laterally
Movements at the lower cervical vertebral column
Extension-ovrlying vertebral 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
nuchae,
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
Any movement b/C7 and T1 amounts for mixed rotation and lateral flexion of
C7
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
7. RANGE OF MOTION
FROM- WHITE AND PUNJABI
stability
Cervical region bears less weoight and are more mobile
Stability is provided by bony configuration, muscles , ligaments
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 ring of the atlas
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
JOINT COMBINED
FLEXION
EXTENSION
ONE SIDE LAT
BENDING
ONE SIDE 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
8. Muscles of cervical vertebrae
*Muscles-flexion of head and neck-
Depends on anterior muscles of the neck
They are:
1. rectus capitis major, rectus capitis minor
2. Longus cervicis which plays an important role in straightening the cervical
column and holding it rigid
3. Scalene anterior posterior and medius
4. Suprahyoid and infrahyoid muscles helps in supporting the cervical column
at rest
5. sternocliedomastoid
Rectus Capitis Posterior Major
Origin: Spinous process of axis (C2)
Insertion: Lateral half of the inferior nuchal line of
the occipital bone
Action: Extension of the head
Innervation: Posterior Primary Ramus of C1
Primary Actions of the Rectus Capitis Posterior
Major:
1. Extension of the head on the neck when acting bilaterally
2. Ipsilateral rotation of the cervical spine when acting unilaterally
Rectus Capitis Posterior Minor:
Origin: Posterior tubercle of atlas (C1)
Insertion: Lateral half of the inferior nuchal line of
the occipital bone.
Action: Extension of the head
Innervation: Posterior Primary Ramus of C1
Primary Actions Rectus Capitis Posterior Minor:
1. Extension of the head on the neck when acting bilaterally
2. Ipsilateral rotation of the cervical spine when acting
unilaterally
9. Splenius Cervicis
Origin: Spinous processes and supraspinous
ligaments of T3 to T6
Insertion: Posterior tubercles of transverse processes
of C1 to C3
Action: Extention of the cervical spine,Lateral flexion
of the cervical spine, Rotation of the cervical spine
Innervation: Dorsal primary rami of C5 to C7
Primary Action of the splenius cervicis:
1. Extension of the cervical spine when acting bilaterally
2. Lateral Flexion of the cervical spine when acting
unilaterally
Secondary Action of the splenius cervicis:
1. Assists with ipsilateral rotation of the cervical spine when acting unilaterally
Scalenes
Scalene Muscle Group:
Scalenus Anterior
Origin: Anterior tubercles of
the transverse processes of (C3-C6)
Insertion: Scalene tubercle and cranial
crest of first rib
Action: Flexion of the cervical spine,
Lateral flexion of the cervical spine,
Innervation: Ventral rami of(C3-C8)
Primary Actions of the Scalenus
Anterior:
1. Flexion of the cervical spine when acting bilaterally
2. Lateral Flexion of the cervical spine when acting unilaterally
Secondary Actions of the Scalenus Anterior:
1. Assists with contralateral rotation of the cervical spine when acting unilaterally
2. Assists with forced inspiration by elevating first rib
10. Scalenus Medius
Origin: Posterior tubercles of the transverse processes
of (C2-C7)
Insertion: Cranial surface of the first rib
Action: Flexion of the cervical spine, Lateral flexion of
cervical spine
Innervation: Ventral rami of (C3-C8)
Primary Actions of the Scalenus Medius:
1. Flexion of the cervical spine when acting bilaterally
2. Lateral flexion of the cervical spine when acting unilaterally
Secondary Actions of the Scalenus Medius:
1. Assists with contralateral rotation of the cervical spine
when acting unilaterally
2. Assists with forced inspiration by elevating the first rib
Scalenus Posterior
Origin: By tendons from the posterior
tubercles of the transverse processes of
(C4–C6)
Insertion: Outer surface of 2nd rib
Action: Lateral flexion of the neck
Innervation: Ventral rami of (C3-C8)
Primary Actions of the Scalenus Posterior:
1. Lateral flexion of the cervical spine when acting unilaterally
Secondary Actions of the Scalenus:
1. Assists with contralateral rotation of the cervical spine when acting unilaterally
2. Assists with forced inspiration by elevating the second rib
Sternocleidomastoid
Sternal Head:
Origin: Upper part of the anterior surface of
the manubrium
Clavicular Head:
Origin: Superior surface of the medial one third
of clavicle
Insertion: Lateral surface of the mastoid
process of the occipital bone, from its apex to
its superior border, and by a thin aponeurosis to the lateral half of the
superior nuchal line
11. Action: Bilaterally: flexion of the head and neck, extension of the head and
neck
Unilaterally: rotation of head to opposite side, lateral flexion
Innervation: Accessory nerve: cranial nerve XII and ventral rami of the (C2,
C3)
Primary Actions of the Sternocleidomastiod:
1. Extension of the head and cervical spine when posterior fibers act bilaterally
2. Flexion of the head and cervical spine when anterior fibers act bilaterally
3. Lateral flexion of the head and cervical spine when acting unilaterally
4. Contralateral rotation of the head and cervical spine when acting unilaterally
*Extension of head and neck-
Brought about by posterior neck muscles
They are:
1- splenius cervicis,
2- semispinalis cervicis,
3- leavator scapulae,
4- transverso spinalis,
5- longismus capiis,
6- spenius capitis,
7- 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
Splenius Cervicis
Origin: Spinous processes and supraspinous
ligaments of T3 to T6
Insertion: Posterior tubercles of transverse
processes of C1 to C3
Action: Extention of the cervical spine,Lateral
flexion of the cervical spine, Rotation of the
cervical spine
Innervation: Dorsal primary rami of C5 to C7
Primary Action of the splenius cervicis:
1. Extension of the cervical spine when acting bilaterally
2. Lateral Flexion of the cervical spine when acting unilaterally
12. Secondary Action of the splenius cervicis:
1. Assists with ipsilateral rotation of the cervical spine when acting unilaterally
Semispinalis Cervicis :
Origin: By fleshy and tendinous fibers to the
transverse processes of (T1 – T6)
Insertion: Spinous processes of C2 to C5, spanning
four to six levels between attachment points
Action: Extension of the cervical spine, lateral
flexion of the cervical spine, rotation of the cervical
spine
Innervation: Dorsal primary rami of (C3-C5)
Primary Actions of the Semispinalis Cervicis:
1. Extension of the cervical spine when acting bilaterally
2. Lateral flexion of the cervical spine when acting unilaterally
3. Contralateral rotation of the cervical spine when acting unilaterally
4. Extension of the thoracic spine when acting bilaterally
5. Contralateral rotation of the trunk when acting unilaterally
Secondary Actions of the Semispinalis Cervicis:
1. Assists with lateral flexion of the thoracic spine when acting unilaterally
Levator Scapulae
Origin: Posterior tubercles of the transverse
processes of C1-C4
Insertion: Superior part of the medial border of the
scapula
Action: Elevation of the scapula, downward
rotation of the scapula
Innervation: Anterior primary rami of (C3 and C4),
dorsal scapular nerve (C5)
Primary Actions of the Levator Scapulae:
1. Elevation of the scapula
Secondary Actions of the Levator Scapulae:
1. Downward rotation of the scapula
13. Transverso spinalis
ORIGIN Transverse processes
INSERTION Spinous processes above and occipital bone (only semispinalis capitis
part shown)
NERVE Posterior primary rami
ACTION:
1. One side - Lateral flexion of the cervical and thoracic spine
2. Both Sides - Extension and hyperextension of atlantooccipital joint
and thoracic spine.
Longissimus Capitis
Origin: By tendons from the posterior
surfaces of the transverse processes of T1
to T5 and the articular processes of C4 or
C5-7
Insertion: Posterior margin of the mastoid
process of the occipital bone
Action: Extension of the head and cervical
spine
Innervation: Dorsal primary rami of C4 to
T5
Primary Actions Longissimus Capitis:
1. Extension of the head and cervical spine when acting bilaterally
Secondary Actions Longissimus Capitis:
1. Assists with ipsilateral rotation of the cervical spine and head when acting
unilaterally
SPLENIUS CAPITIS
ORIGIN Lower ligament nuchae, spinous processes and
supraspinous ligaments T1-3
INSERTION Lateral occiput between superior and inferior
nuchal lines
ACTION Extends and rotates cervical spine
NERVE Posterior primary rami of C3, 4
Trapezius
14. Origin:
Upper part: External occipital proturberance,
medial third of the superior nuchal line, the
ligamentum nuchae, and the spinous process
of C7
Medial Part: Spinous processes of T1 to T5.
Lower Part: Spinous processes of T6 to T12
Insertion:
Upper Part: Lateral third of the clavicle and
the medial aspect of the acromion process of
the scapula
Middle Part: Medial edge of the superior surface of the acromion process of
the scapula and the superior edge of the scapular spine.
Lower Part: Tubercles of the apex of the scapular
spine
Action:
Upper Part: Upward rotation of the scapula,
elevation of the scapula
Middle Part: Retraction of the scapula
Lower Part: Upper rotation of the scapula,
depression of the scapula
Innervation: Spinal Accessory Cranial XI , Ventral
Rami C2-C4
Primary Actions of the Upper Trapezius
1. Upward rotation of the scapula
2. Elevation of scapula
Secondary Actions:
1. Assists with elevation of the cervical spine (distal attachment fixed, acting
bilaterally)
2. Assists with lateral flexion of the cervical spine (distal attachment fixed,
acting unilaterally)
3. Assists with contralateral rotation of the head and cervical spine when acting
unilaterally
Primary Actions of the Middle Trapezius
1. Retraction of scapula
Primary Actions of the Lower Trapezius
1. Upward rotation of the scapula
2. Depression of the scapula