Transcript Spine Lecture

The
Trunk/Spine
• largest segment of body
• most significant functional
unit for general movement
• integral role in upper and
lower extremity function
• relatively little movement
between 2 vertebrae
1
The Vertebral
Column
7 cervical vertebrae
develop as an infant begins to lift its head
Cervicothoracic junction
12 thoracic vertebrae
present at birth
Thoracolumbar junction
5 lumbar vertebrae
develop in response to weight bearing
Lumbosacral junction
Sacrum - 5 fused vertebrae
Coccyx - 4-5 fused vertebrae
2
Vertebral
Articulation
• each articulation
is a fully
encapsulated
synovial joint
• these are often
called
apophyseal joints
Superior articular process
Inferior articular process
Note: the processes are bony outcroppings.
3
Costal (Rib)
Articulation
Superior
costal
facet
Transverse
costal
facet
Note: the facets are
the articular surfaces.
Inferior
costal
facet
4
Body
Transverse process
Vertebral foraman
Spinous process
Intervertebral foraman
5
Muscular Attachments
• muscular attachments on spinous and
transverse processes
6
Vertebral shape
changes to reflect
movements possible
within a given region
7
Further
depiction
of vertebral
shapes
8
Motion Segment: Functional unit of the vertebral column
Neural arches
intervertebral joints
transverse & spinous processes
ligaments
Two bodies of vertebrae
common vertebral disc
ant & post longitudinal ligaments
9
Intervertebral Disks
‘shock absorbers’ of the spine
capable of withstanding compressive
torsional and bending loads
role is to bear and distribute loads in
vertebral column and restrain
excessive motion in vertebral segment
10
Shock Absorbers
Bending Loads
11
•2 regions of vertebral disk
NP -- nucleus pulposus
•gel-like mass in center of disk under
pressure such that it preloads disk
•80-90% water, 15-20% collagen
AF -- annulus fibrosus
•fibrocartilaginous material
•50-60% collagen
Disc is avascular & aneural
so healing of a damaged disc is
unpredictable & not promising
Disc rarely fails under compression
vertebral body will usually fracture
before damage to disc occurs
12
Anterior Motion Segment
Ant. Longitudinal ligament
very dense & powerful
attaches to ant disc & vert body
limits hyperextension and fwd mvmt
of vertebrae relative to each other
Post. Longitudinal Ligament
travels inside the spinal canal
connects to rim of vertebral bodies &
center of disc
posterolateral aspect of segment not
covered - this is a common site for
disc protrusion
offers resistance to flexion
13
Posterior Motion Segment
Bone tissue in the
pedicles and laminae
is very hard providing
good protection
for spinal cord
Muscle attachments at spinous &
transverse processes
articulation between vertebrae occurs
at superior and inferior facets
these facets are oriented at different
angles related to spinal section
accounting for functional differences
14
Posterior Motion Segment
Ligamentum flavum spans laminae
connecting adjacent vertebral arches
very elastic thus aids in extension
following flexion of the trunk
under constant tension to maintain
tension on disc
Supraspinous and interspinous
ligaments span spinous processes
resist shear and forward bending
of spine
15
Spinal
Movement
•
•
•
•
collectively -- LARGE ROM
flex/ext
L-R rotation
L-R lateral flexion
16
MOVEMENTS OF THE SPINE
ACCOMPANIED BY PELVIC TILTING
1st 50-60º in
lumbar vertebrae
Flexion beyond 50º
due to anterior
pelvic tilting
17
Regional ROM in Spine
Atlas (C1) & axis (C2)
account for 50% of
rotation in the cervical
region.
Thoracic region is
restricted, mainly due
to connection to ribs.
18
Spine Posterior Muscular
Support
primarily produce extension
and medial/lateral flexion
• Superficial to deep
– erector spinae
– semispinalis
– deep posterior
19
Spine Posterior Muscular Support
primarily produce extension and
medial/lateral flexion
• Posteriorly
– erector spinae
iliocostalis
longissumus
thoracis
spinalis
20
spinalis
longissimus
Erector spinae
Versatile muscles that can generate
rapid force yet are fatigue resistant
cervicis
iliocostalis
thoracis
lumborum
21
Semispinalis
capitis
cervicis
thoracis
22
IT
IS
intertransversarius
interspinales
Deep posterior
multifidus
rotatores
23
rectus abdominis
Abdominals
transverse abdominus
internal oblique
external oblique
24
Intra-Abdominal Pressure
acts like a “balloon” to expand
the spine thus reducing compressive
load, this in turn reduces the activity
in the erector spinae
Internal & external oblique
muscles & transverse abdominis
attached to the thoracolumbar
fascia covering the posterior
region of the trunk
when these abdominals contract - added
support for the low back is created
25
Additional muscles contributing to trunk flexion
Collectively known as the iliopsoas
Powerful flexor
whose action is
mediated by the
abdominals
Quadratus lumborum
forms lateral wall of abdomen
also maintains pelvic position
during swing phase of gait
26
Movement into fully flexed position
1) initiated by abdominals (1/3 of flexor moment) and iliopsoas
2) once it has begun gravity becomes a contributing factor
such that the erector spinae act eccentrically to control
the movement (thru ~50-60º)
3) beyond 50-60º flexion continues by anterior tilt of pelvis
this mvmt is controlled by an eccentric action of hamstrings and gluteus
maximus while erector spinae contribution diminishes to zero
4) in this fully flexed position the posterior spinal ligaments and the passive
resistance in the erector spinae resist further flexion
5) this places the ligaments at or near the failure strength placing a greater
importance on the load sustained by the thoracolumbar fascia loads
supported thru the lumbar articulations
6) return to standing posture initiated by posterior hip muscles
7) erector spinae (1/2 of extensor moment) muscle active initially but peak
activity during the final 45-50º of movement
27
Strength of Trunk Movements
Extension
Flexion (70% of extension)
Lateral Flexion (69% of extension)
Rotation (43% of extension)
28
Postural
Alignment
• 2 naturally occurring curves
– LORDOTIC (in lumbar
region)
– KYPHOTIC (in upper
thoracic lower cervical
regions)
– Abnormalities -- accentuated
vertebral curves
29
Lumbar
Lordosis
• exaggeration of the lumbar
curve
• associated w/weakened
abdominals (relative to
extensors)
• characterized by low back
pain
• prevalent in gymnasts,
figure skaters, swimmers
(flyers)
30
Thoracic
Kyphosis
• exaggerated thoracic curve
• occurs more frequently than
lordosis
• mechanism -- vertebra
becomes wedge shaped
• causes a person to “hunch
over”
31
Kyphosis
• aka “Swimmer’s Back”
• develops in children
swimmers who train with
an excessive amount of
butterfly
• also seen in elderly women
suffering from osteoporosis
32
Scoliosis
• lateral deviation of the
spinal column
• can be a ‘C’ or ‘S’ shape
• involves the thoracic and/or
lumbar regions
• associated w/disease, leg
length abnormalities,
muscular imbalances
33
Scoliosis
• more prevalent in females
• cases range from mild to
severe
– small deviations may
result from repeated
unilateral loading (e.g.
carrying books on one
shoulder)
34
Consequences of
Pelvic Tilt
• in normal standing the line of gravity
passes ventral (anterior) to the center
of the 4th lumbar vertebral body
Tm
• This creates a forward bending
torque which must be counterbalanced by ligaments and
muscles in the back
• any movement or displacement
of this line of gravity affects the
magnitude of the bending
moment (or torque)
• slouched posture support comes
from ligaments – this is bad for
extended periods of time
TW
35
Pelvic Tilt and
Lumbar
Loading
• relaxed standing:
the angle of
inclination of the
sacrum (sacral
angle) is 30 to the
transverse plane
36
Pelvic Tilt and
Lumbar
Loading
• posterior pelvic tilt
reduces the sacral angle
or flattens the lumbar
spine (reduces lordosis)
• causes the thoracic
spine to extend which
adjusts line of gravity
such that muscle
expenditure is minimized
• BUT load is now passed
on to ligaments
37
Pelvic Tilt and
Lumbar
Loading
• anterior pelvic tilt
increases sacral angle
• accentuate lumbar
lordosis and thoracic
kyphosis
• this adjusts line of gravity
to increase muscle
energy expenditure
38
Pelvic Tilt and
Sitting
• Sitting (relative to standing)
– pelvis posteriorly tilted
– lumbar curvature is
flattened
– line of gravity (already
ventral to lumbar spine)
shifts further ventrally
– increases the moment
created by body weight
about the lumbar spine
– increased muscular
support increases the
load on the spine
vs.
39
Pelvic Tilt and
Sitting
• erect sitting
– pelvis tilts anteriorly
– increases lumbar
curvature
– reduces the moment
arm of body weight
– reduces need for
muscular support
– reduces load on lumbar
spine
– however, pelvis still
much more tilted than
during normal erect
standing
vs.
40
L3 Load
• lowest when lying
supine
• normal when
standing upright
• 140% when
sitting with no
back support
• 150% when
hunched over
• 180% when sitting
hunched over with no
back support
41
• apparent that lumbar load is strongly related to support needed
to maintain lumbar lordosis
• in erect, supported sitting the addition of a back rest reduces
lumbar load
• reclining seated position reduces disc pressure even further
42
Spinal Injuries
43
Progression
of Disc
Degeneration
44
Degenerative Disks
• lose ability to retain • ability to distribute
• disk integrity
water in disk so
load across disk
decreases with
disks “dry out”
changes
age
45
46
Herniated Disks
• NP protrudes out
from between the
vertebrae
• nerves are
impinged by the
bulging NP
• lead to numbness
and/or pain
47
Tearing of Annulus
Disk Herniation
48
49
50
51
Whiplash
Rapid flexion/extension injuries in cervical region
strain posterior ligaments
dislocate posterior apophyseal joints
7th cervical vertebra is likely site for fracture in this injury
52
Low Back Pain
Vertebral instability
1) Muscle strain from
lifting may create muscle
spasms
2) distorted posture for long
periods of time
3) avoid crossing legs at the
knee
4) tight hamstrings or
inflexible iliotibial band
5) weak abdominals
53
Lift With Your Legs
• What does this mean?
– the idea is to keep the weight (W) as close
to the axis of rotation as possible
smaller
muscular
torque
muscular
torque
axis
W
axis
W
54