Biomechanics of spine

Biomechanics of spine

1. Cervical & Thoracic

3. The Curves
a ae

¢ Primary and

+ Secondary curves.

4. Typical vetebrae

8 A. The anterior portion

Neural arch of a vertebra is called

5 the vertebral body.

Vertebral Posterior

body Pedicles elements

B. The posterior portion
of a vertebra is called
the vertebral or neural
arch.

The neural arch is
further divided into the
pedicles and the
posterior elements.

5. Typical vetebrae

° The posterior
elements are the
laminae, the
articular
processes, the
spinous process,
and the
transverse
processes.

6. Vertical Trabeculae

The various
trabeculae are
arranged along
the lines of force
transmission.

7. The Inter vertebral Disk

8. The Inter vertebral Disk

A. Under compressive
loading, the NP attempts
to expand. Tension in the
AF rises.

. A force equal in
magnitude but opposite in

direction is exerted by the
AF on the NP, which
restrains radial expansion
of the NP and establishes
equilibrium.

The nuclear pressure is
transmitted by the AF to
the end plates.

9. IVD Problems

=—— Normal Disk

+— Degenerated Disk

=— Bulging Disk

+— Herniated Disk

=— Thinning Disk

= Disk Degeneration
with Osteophyte
Formation

Examples of Disk Problem:

10. Ligaments

Ligamentum Flavum

\ ntertransverse
ow | Ligament
dd ig
Facet | q
Capsulary, Pa

Ligament dl Posterior
| mL AE (Longitudinal
\ 2 Ligament,

InterspinoB89

Ea IE
De

Supraspinous { Anterior’

Ligament Longitudinal
Ligament!

11. ° Interbody Joints

+ Zygapophyseal
Articulations

12. Kinematics

Flexion
Extension
Lateral flexion

Rotation.

13. Kinematics

A. The addition of an
intervertebral disk
allows the vertebra
to tilt, which
dramatically
increases ROM at
the interbody joint.
Without an
intervertebral disk, =
only translatory
motions could
occur.

14. Kinematics
Coupled Motion

Lateral flexion is
coupled with

LE axial rotation

LEFT LATERAL NEUTRAL RIGHT LATERAL
FLEXION FLEXION

15. Kinetics

A
Axial Compression SS,
Bending
Torsion
Shear

16. Kinetics

. Side-to-side translation (gliding)
occurs in the frontal plane.

. Superior and inferior
translation (axial distraction
and compression) occur
vertically.

>. Anteroposterior translation
occurs in the sagittal plane.

. Side-to-side rotation (tilting) in E
a frontal plane occurs around |
an anteroposterior axis.

E. Rotation occurs in the
transverse plane around a
vertical axis.

F. Anteroposterior rotation
(tilting) occurs in the sagittal
plane around a frontal axis.

17. Biomechanics of spine

18. Structure

Two distinct regions:
° The upper cervical,
or craniovertebral

region and
The lower cervical
region

19. Craniovertebral Region
ATLAS.

Inferior zygapophyseal facets
Superior zygapophysaal facets

Transverse
process

The atlas is a markedly atypical vertebra.
It lacks a body and a spinous process.

20. Craniovertebral Region

° The dens
(odontoid process)
arises from the
anterior portion of
the body of the
axis.

Dens (odontoid process)

The superior
zygapophyseal
facets are located
on either side of
the dens.

21. Craniovertebral Articulations

Median

Transverse / atlantoaxial
foramen 5 articulation

Atlas —,

Vertebral
artery

Spinous “

process

The median atlantoaxial
articulation is seen, with
the posterior portion
(transverse ligament)
removed to show the dens
and the anterior arch of
the atlas.

The two lateral
atlantoaxial joints between
the superior
zygapophyseal facets of
the axis and the inferior
facets of the atlas can be
seen on either side of the
median atlantoaxial joint.

22. Craniovertebral Ligaments

Atlantal cruciform
ligament

« Alar ligaments

23. Craniovertebral Ligaments

A. Posterior
atlanto-occipital
and atlantoaxial
membranes.

B. Anterior atlanto-
occipital and
atlantoaxial
membranes.

24. Craniovertebral Ligaments

¢ The tectorial
membrane is a
continuation of
the posterior
longitudinal
ligament.

25. The Lower Cervical Region

Transverse

process Body anses Uncinat processes Superior

foramen articular

ps Aca process
Y (racer)

’ articular
; nt process
| foramen wow (facet)

IN
alt

Superior
articular =
process ®

Lamina

Body
Spinous processes

Posterior Sagittal
view view

The body of a
typical cervical
vertebra is small
and supports
uncinate processes
on the

Postero lateral
superior and

inferior surfaces.

26. Intervertebral Disk

A. Superior view
shows crescent-
shaped anulus
fibrosus.

. B. Lateral view
shows
uncovertebral
cleft.

27. Interbody Joints

Lateral view of an inter body
saddle joint of the lower cervical
spin

Anterior view showing how the
convex inferior surface of the
superior vertebra fits into the
concave superior surface of the
inferior vertebra.

The cervical vertebra
exhibit raised
superolateral lips
known as uncinate
processes.

These articulate with
the margins of the
vertebral body
above, forming the
uncovertebral joint
or "joint of
Luschka."

28. Zygapophyseal Joints

29. Kinematics

Nodding motions of

the atlanto-occipital

joints.

A. Flexion.
B. B. Extension.

30. Kinematics

Superior view of rotation
at the atlantoaxial joints:
The occiput and atlas
pivot as one unit around
the dens of axis.

31. Kinematics

A. Flexion of the lower
cervical spine combines
anterior translation and
sagittal plane rotation
of the superior
vertebra.

Extension combines
posterior translation
with sagittal plane
rotation.
The range for flexion
and extension increases
from the C2/C3 segment
to the C5/C6 segment,
and decreases again at
the C6/C7 segment

32. Kinetics

* cervical region bears less weight and is
generally more mobile.

No disks are present at either the atlanto-
occipital or atlantoaxial articulations;

The trabeculae show that the laminae of
both the axis and C7 are heavily loaded

34. Structure

BE y ¢ The Ist and 12th
are transitional

vertebrae
ls Dim 10%, in
12th are atypical
vertebrae

35. Typical Thoracic Vertebrae

Superior tacts

Super
Jamas

A.

Lateral view of the thor
vertebra shows the superior
and inferior facets of the
zygapophyseal joints and the
demifacets for articulation with
the ribs.

Overlapping of spinous
processes in thoracic region.

Superior view of a thoracic
vertebra, showing the small,
ular vertebral foramen, the
costotubercular facets for
articulation with the tubercles
of the ribs, and the superior
costocapitular facets for
articulation with the he:
the

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37. Articulations

° Interbody Joints

° Zygapophyseal
Joints

38. Kinematics

the range of flexion and
Anterior extension is extremely
“E limited

Stornum

|| Right

à Rotation of a thoracic
Ge 7 yertebral body to the left

= NN = produces a distortion of
the associated rib pair
that is convex posteriorly |
on the left and convex |
anteriorly on the right.

39. Kinetics

° The thoracic region is subjected to
increased compression forces in
comparison with the cervical

region, because of the greater
amount of body weight that needs
to be supported and the region’s

kyphotic shape.

40. http://www.pt.ntu.edu.tw/hmchai/kines04/KINoutline.htm