Download Functional Anatomy of the Trunk

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Functional Anatomy of the
Trunk
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7 cervical vertebrae, a convex curve o
the anterior side of the body
develops as an infant begins to lift its
head
support the head and assumes its
curvature in response to head position
12 thoracic vertebrae convex to the
posterior side
5 lumbar vertebrae convex anterior side
develops in response to weight bearing
influenced pelvic and lower extremity
positioning
Junction site of great mobility
vulnerable to injury
→Cervicothoracic, thoracolumbar, and
lumbosacral regions
 curves exaggerated → more mobile
curves flat → more rigid
 Cervical and lumbar most mobile →
thoracic and pelvic more rigid
 Besides support and flexibility, main
responsibility protecting the spinal cord
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The vertebral column acts as a modified
elastic rod, providing rigid support and
flexibility.
33vertebrae, 24 movable contribute to
trunk movements
Arranged into 4 curves facilitate support
by offering a springlike response to
loading
Provide balance and strengthen the
spine
The last curve is the sacrococcygeal
curve
Canal formed →
body, pedicles, pillars of the vertebrae,
disc, ligament, ligamentum flavum
Peripheral nerves exit through the
intervertebral foramen on the lateral
side of the vertebrae
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The Vertebral Column
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Trunk play a integral role in both upper
and lower extremity function
Anatomical and Functional Characteristics
of The Joints
 First two cervical vertebrae have unique
structure
Motion
segment
Motion Segment：Anterior
Portion
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Two bodies, intervertebral disc, anterior
and posterior longitudinal ligaments
Vertebral body is tube-shaped and
thicker on the front side
Absorbs large amounts of compressive
forces
The disc is withstanding compressive
forces as well as torsional and bending
forces applied to the column
bear and distribute loads in the
vertebral column
restrain excessive motion in the
vertebral segment
Load transmitted via the intervertebal
discs distributes stress uniformly over
the vertebral end plates
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It consists of cancellous tissue
surrounded by a hard cortical layer and
has a raised rim that facilitates
attachment of the disc, muscles, and
ligaments
Surface of the body is covered with
hyaline cartilage, forming articular end
plates into which the disc attaches
responsible for most of the mobility in
the spine
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Each disc consists of the nucleus
pulposus and the annulus fibrosus
 Gel-like spherical mass in the
→central portion of the cervical and
thoracic discs
→posterior in the lumbar discs
 nucleus pulposus 80 to 90％ water, 15
to 20％ collagen, creating a fluid mass
always under pressure exerting a
preload to the disc
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well suited for withstanding compressive
forces
The day, water content reduced with
compressive forces during daily activities,
resulting shortening of the column by
about 15 to 25mm
height and volume reduced 20％ bulge
radially outward, increase the axial
loading on the posterior joints
At night, imbibes water, restoring
height to the disc
The elderly is less（approximately 70
％） imbibe reduced, leaving a shorter
vertebral column
Trunk rotation, annulus fibrosis become taut and the rest relax
Compressive – tension force
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Motion Segment：Posterior
Portion
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Includes the
neural arches,
the intervertebral
joints, transverse
and spinous
processes and
ligaments
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Facets different angles in the cervical,
thoracic, and lumbar regions of the
functional differences
Prevent the forward displacement of
one vertebra over another and
participate in load bearing
Hyperextended position, joints bear 30
％ of the load
Highest pressures in the joints occur
with combined torsion, flexion, and
compression
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Movements of The Total Spine
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Motion is small, restricted by the discs
and the arrangement of the facets
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110-140°
75-85°
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90°
Pedicles and laminae is very hard
→providing good resistance to the large
tensile forces
The spinous and transverse processes
serve as attachment sites for the spinal
muscles running the length of the
column
Two synovial joints formed by facets on
the upper and lower border of each
laminae
Ligamentum flavum →
elastic qualities, allowing it deform and
return to its original length
In the neutral position, under constant
tension, imposing continual tension on
the disc
Trunk flexion occurs primarily in the
lumbar vertebrae
first 50 to 60° moved into more flexion
by forward tilt of the pelvis
Extension first the pelvis tilts posteriorly
Flexion begins placing compressive
force on the anterior portion of the disc
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Ligaments and annulus fibers absorb
the compressive forces
Lateral flexion range of motion is about
75-85° mainly in the cervical and lumbar
regions
Cervical Region
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Rotation is limited in the lumbar region
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C1, C2→ no
vertebral body,
shaped like a ring
C2→large
transverse
processes with
transverse foramen
which blood supply
travels
C1, No spinous process, hold the
occiput of the skull
Atlanto-occipital joint
Head nods, allows free sagittal plane
movements 10 to 15° of flexion
/extension, 8° of lateral flexion, no
rotation
Atlantoaxial joint
the most mobile of the cervical joints,
10° of flexion/extension, 47° of rotation,
no lateral flexion
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Transverse process of the cervical
vertebera
→Foramen where the arteries pass
through, this is not found in other
regions
Difference between the C-T-L
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Cervical discs, thicker ventrally than
dorsally
producing a wedge shape and
contributing to the lordotic curvature in
the cervical region
Short spinous processes
Maximum rotation C1-C2
maximum lateral flexion C2-C4
maximum flexion/extension
at C1-C3 and C7-T1
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Thoracic Region
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The most restricted regions
bodies become taller, longer pedicles,
transverse processes are long, angle
backward
On the back, long spinous processes
overlapping, directed downward
Flexion/extension combined is 3 to 12°,
very limited motion in the upper
thoracic（2-4°）
increases in the lower thoracic to 20° at
the thoracolumbar junction
Lateral flexion is limited, ranging from 2
to 9°
Upper T, lateral flexion is limited to 2 to
4°
Lower T it may be as high as 9°
Lumbar region
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Large lumbar vertebra most highly
loaded structure, pedicles are short,
spinous processes broad, small
transverse processes
Gender differences and different disc
heights at different levels of the
vertebrae→higher in ♂ ,highest disc
height is found at L4-L5 and L5-S1
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Apophyseal joints→
60° to the transverse plane
20° to the frontal plane
Movements limited primarily by he
connection with the ribs
orientation of the facets
long spinous processes that overlap in
the back
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Rotation from 2 to 9°
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Disc injuries is not common
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Flexion/extension 8 to 20°
lateral flexion from 3 to 6°
very little rotation（1 to 2°）at all levels
of the lumbar vertebrae
Lumbosacral joint is the most mobile
Flexion/extension→75％
20％ at L4-L5
5％ at the other
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Combined Movements Of The
Pelvis And Trunk
MUSCULAR ACTIONS
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Lumbar flatten
Trunk extension is an important
movement
raise the trunk and to maintain an
upright posture
Anterior tilt of the pelvis
Trunk Extension
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Spinal extensors
1. erector spinae
（iliocostalis, longissimus, spinalis）
2.deep posterior, paravertebral,
muscles
（intertransversarii, interspinales,
rotators, multifidus）
Trunk Flexion
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Consist of 4 muscles
1. the rectus abdominus
2. the internal oblique
3. the external oblique
4. the transverse abdominus
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Increase intra-abdominal pressure when
contract
decrease the compressive force on the
spine
reduces the activity of the erector
spinae muscles
Transverse abdominus plays a greater
role
→↑ intra-abdominal pressure than the
obliques
Trunk Lateral Flexion
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Most activity in lateral flexion
→lumbar erector spinae muscles
deep→ intertransversarii and
interspinales muscles on the
contralateral side
STRENGTH AND FORCES AT
THE VERTEBRAL JOINTS
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Greatest strength output in the trunk
extension
→ averaging values of 210 Nm for
males
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Quardratus lumborum
→ form lateral wall of the abdomen and
runs from the iliac crest to the last rib
maintaining pelvic position on the
swing side in gait.
Trunk Rotation
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More complicated
Trunk flexion strength was 150 Nm, or
approximately 70％ of the strength of
the extensors
Lateral flexion was 145 Nm, or 69％ of
the extensor strength
rotation was 90 Nm 43％ of the
extensor strength
Female→ approximately 60％ recorded
for males
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Discs, apophyseal joints and
intervertebral ligaments
→ load-bearing structures
 Compressive forces are perpendicular to
the disc
 Lumbar vertebrae handle the largest
load
→ because positioning, center of mass
relative to the lumbar region and
greater body weight acting at the
lumbar region
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Loads Acting on the Vertebrae
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Loads produced by body weight
muscular force acting on each motion
segment
prestress forces due to the disc and
ligament forces
Muscle forces protect the spine from
excessive bending and torsion subject
the spine to high compressive forces
Axial load in standing is 700N
Lumbar spine can resist approximately
9800N of vertical load before fracturing
Various postures and Exercises
Shearing force across LS
joint is 50% BW
Sacral °↑50 °, Shearing
force ↑75% BW
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Loading on Lumbar
POSTURE
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1470 N
1176 N
Unsupported sitting position more load
than standing
686 N
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1715 N
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1764 N
because a backward tilt, a flattening of
the low back and forward shift in the
center of gravity
1813 N
Sitting long→
↑the resting length of the erector
spinae muscles and overstretch the
posterior ligamentous structures
Continuous flexion cause of both
lumbar and cervical flexion injuries in
the workplace
C- or S-shaped depending on the
direction and the beginning and ending
segments
Postural Deviations
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Rounded-shoulder may cause thoracic
kyphosis associated with osteoporosis
other disorders
Exaggerated lumbar curve
→Lumbar lordosis or hyperlordosis
most serious postural disorders →
scoliosis
CONDITIONING
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The cause
of scoliosis
is unknown,
♀＞♂
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Force production→
Low back is a common site of injury in
sports and in the workplace, special
attention should be given to exercises
strengthen and stretch
trunk exercises should evaluated for
negative impact on trunk function and
structure
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Ball
exercise
Excessive lordosis, hyperextension of
the lumbar should be avoided, pay
attention to its risks
CONTRIBUTION OF TRUNK
MUSCLES TO SPORTS SKILLS
OR MOVEMENTS
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Lumbar muscles serve to restrict
locomotion
→controlling lateral flexion/the forward
flexion of the trunk
Cervical muscles serve to maintain the
head in an erect position on the trunk
INJURY POTENTIAL IN THE
TRUNK
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Back sprain accounts for only 2 to 3％
of the total sprains in the athletic
population
 in sports→ require high levels of
bending and rotation, such as golf,
gymnastics, and baseball
 Compression on the spinal cord or
nerve roots from an intervertebral disc
protrusion or disc prolapse
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speed of walking↑,corresponding ↑ in
lumbar range of motion
One difference
→ in walking
trunk extension at touchdown
→ in running
trunk will be flexed at touchdown
only at fast speeds
At slower speeds, the trunk will be
extended at touchdown.
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The incidence of injury is very high, 60
to 80％ will have back pain at some
time in their lives
Low-back pain is most common→ age
range of 25 to 60
uncommon in children and athletes
Disc protrusions→ most frequently at
C5-C6, C6-C7, L4-L5, and L5-S1
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Disc protrusion impinge nerve
Significant amount of torsion, or
rotation, of the trunk has been shown
to tear fibers in the annulus fibrosus of
the disc
Pure compression to the spine usually
injures the vertebral bodies and end
plates rather than the disc
Disc
degeneration
Fatigue fracture
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椎弓解離
脊椎滑脫
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Most common in repeated flexion,
extension and rotation
20.7% incidence of spondylolysis in
athletes
Spondylolysis on both sides,
spondylolisthesis can develop
In cervical region, whiplash injury are
common
Rapidly flexed, straining the postreior
ligaments even dislocation
In thoracic region, is not injured as
frequency as C and L region
Stabilization and limitated as a result of
interface with the ribs
In lumbar region, is the most injured
→myofascial pain, muscle spasm,
irritation of the joints, disc prolapse,
sciatic, low-back pain..
whiplash injury
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Effect of Aging on The Trunk
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flexibility↓
Loss of strength in the trunk muscle of
approximately 1% per year
Disc, small fluid, place more stress on
the annulus fibrosus
Mobility ↓ in segments
↓loading imposed on the low back
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