biomechanics of spine
TRANSCRIPT
Biomechanics of spine
Cervical & Thoracic
1
12 Thoracic
5 Lumbar
5 Sacral
7 Cervical
4 Coccygeal2
The Curves
• Primary and
• Secondary curves.
3
Typical vetebrae
A. The anterior portion
of a vertebra is called
the vertebral body.
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.
4
Typical vetebrae
• The posterior
elements are the
laminae, the
articular
processes, the
spinous process,
and the
transverse
processes.
5
Vertical Trabeculae
• The various
trabeculae are
arranged along
the lines of force
transmission.
6
The Inter vertebral Disk
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The Inter vertebral Disk
A. Under compressive
loading, the NP attempts
to expand. Tension in the
AF rises.
B. 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.
A B
8
IVD Problems
9
Ligaments
10
Joints
• Interbody Joints
• Zygapophyseal
Articulations
11
Kinematics
• Flexion
• Extension
• Lateral flexion
• Rotation.
12
Kinematics
A. The addition of an
intervertebral disk
allows the vertebra
to tilt, which
dramatically
increases ROM at
the interbody joint.
B. Without an
intervertebral disk,
only translatory
motions could
occur.
13
Kinematics
Coupled Motion
• Lateral flexion is
coupled with
axial rotation
14
Kinetics
• Axial Compression
• Bending
• Torsion
• Shear
15
Kinetics A. Side-to-side translation (gliding)
occurs in the frontal plane.
B. Superior and inferior
translation (axial distraction
and compression) occur
vertically.
C. Anteroposterior translation
occurs in the sagittal plane.
D. Side-to-side rotation (tilting) in
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.
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Biomechanics of spine
Cervical Region
17
Structure
Two distinct regions:
• The upper cervical ,
or craniovertebral
region and
• The lower cervical
region
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Craniovertebral RegionATLAS
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The atlas is a markedly atypical vertebra.
It lacks a body and a spinous process.
Craniovertebral Region
AXIS
• The dens
(odontoid process)
arises from the
anterior portion of
the body of the
axis.
• The superior
zygapophyseal
facets are located
on either side of
the dens.
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Craniovertebral Articulations
• 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.
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Craniovertebral Ligaments
• Atlantal cruciform
ligament
• Alar ligaments
22
Craniovertebral Ligaments
A. Posterior
atlanto-occipital
and atlantoaxial
membranes.
B. Anterior atlanto-
occipital and
atlantoaxial
membranes.
23
Craniovertebral Ligaments
• The tectorial
membrane is a
continuation of
the posterior
longitudinal
ligament.
24
The Lower Cervical Region
The body of a
typical cervical
vertebra is small
and supports
uncinate processes
on the
Postero lateral
superior and
inferior surfaces.
25
Intervertebral Disk
A. Superior view
shows crescent-
shaped anulus
fibrosus.
B. B. Lateral view
shows
uncovertebral
cleft.
26
Interbody Joints
• 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."
27
A. Lateral view of an inter body
saddle joint of the lower cervical
spine.
B. Anterior view showing how the
convex inferior surface of the
superior vertebra fits into the
concave superior surface of the
inferior vertebra.
Zygapophyseal Joints
28
Kinematics
Nodding motions of
the atlanto-occipital
joints.
A. Flexion.
B. B. Extension.
29
Kinematics
• Superior view of rotation
at the atlantoaxial joints:
The occiput and atlas
pivot as one unit around
the dens of axis.
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Kinematics
A. Flexion of the lower
cervical spine combines
anterior translation and
sagittal plane rotation
of the superior
vertebra.
B. 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
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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
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Biomechanics of spine
Thoracic Region
33
Structure
• The 1st and 12th
are transitional
vertebrae
• 1st, 9th, 10th, 11th,
12th are atypical
vertebrae
34
Typical Thoracic Vertebrae
A. Lateral view of the thoracic
vertebra shows the superior
and inferior facets of the
zygapophyseal joints and the
demifacets for articulation with
the ribs.
B. Overlapping of spinous
processes in thoracic region.
C. Superior view of a thoracic
vertebra, showing the small,
circular vertebral foramen, the
costotubercular facets for
articulation with the tubercles
of the ribs, and the superior
costocapitular facets for
articulation with the heads of
the ribs.
35
Intervertebral Disks
36
Articulations
• Interbody Joints
• Zygapophyseal
Joints
37
Kinematics
• the range of flexion and
extension is extremely
limited
• Rotation of a thoracic
vertebral body to the left
produces a distortion of
the associated rib pair
that is convex posteriorly
on the left and convex
anteriorly on the right.
38
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.
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