Kinesiology

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Kinesiology

• The Spine

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Spinal Column Structure

• Base of support.
• Link between upper and lower extremities.
• Protects spinal cord.
• Stability vs. mobility
• Example cervical vs. thoracic spine

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5 Regions of Vertebral Column

• Cervical
• Thoracic
• Lumbar
• Sacral
• Cocygeal
• 33 bones and 23 disks

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Curvatures Viewed Laterally

• Prior to birth C-shaped.
• 4 distinct curves in an adult.

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Cervical Lordosis
Thoracic Kyphosis
Lumbar Lordosis
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Spinal Motion

• Spinal movement is the combination of
• Intervertebral joints
• Facet joints

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Intervertebral Joints
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Intervertebral Disc

• Intervertebral disk make up 20-30 of the height
  of the column and thickness varies from 3mm in
  cervical region, 5mm in thoracic region to 9 mm
  in the lumbar region.
• Ratio between the vertebral body height and the
  disk height will dictate the mobility between the
  vertebra
• Highest ratio in cervical region allows for
  motion
• Lowest ratio in thoracic region limits motion

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Disc Structure

• Nucleus Pulposus (NP) is located in the center
  except in lumbar lies slightly posterior.
• Gelatinous mass rich in water binding PG
  (proteoglycan) AKA (glycoaminoglycos) GAG-protein
  molecule.
• Chondrotin-4 sulfate in PG molecule gives the
  disc a fluid maintaining capacity (hydrophyllic)
  - decreases with age.
• Hydration of the disc will also decrease with
  compressive loading - this loss of hydration
  decreases its mechanical function.

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Disc Structure

• 80-90 is H2O decreases with age.
• Disc volume will reduce 20 daily (reversible)
  which causes a loss of 15-25 mm of height in the
  spinal column.
• Acts as a hydrostatic unit allowing for uniform
  distribution of pressure throughout the disc.

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Disc Structure

• Compressive stresses on the disc translate into
  tensile stresses in the annulus fibrosis
• This makes the disc stiffer which adds stability
  and support to the spine.
• Bears weight and guides motion.
• Avascular - nutrition diffusion through end-plate.

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Annulus Fibrosis

• Collagen arranged in sheets called lamellae
  (outer layers).
• These lamellae are arranged in concentric rings
  -10-12 layers that lessen in number with age and
  thicken (fibrose).
• Enclose the nucleus and oriented in opposite
  directions at an angle of 120 degrees (or 45-65
  degrees).
• Controls the tensile loading from shear,
  accessory motions in the anterior compartment and
  disc forces which can be up to 5x the external
  compression force.

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Annulus Fibrosis

• Mostly avascular and lacking innervation but the
  outermost layers are probably innervated
  (sinovertebral nerve).
• Thickest anteriorly.
• Outermost 1/3 connects to vertebral body via
  Sharpies fibers.
• Outer 2/3 connect to the end plate.

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Disc Pathology - Herniation

• Highest incidence at C5-6, C6-7, L4-5, and
• L5-S1.
• Disc herniation
• Disc protrusion or bulge - contained
• Annulus intact.
• Localized usually lateral
• Diffuse usually posterior
• Prolapsed not contained
• Annular fibers disrupted inner layers
• Extrusion - migration through all layers

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Longitudinal Ligaments
Anterior longitudinal
Supraspinous
Posterior longitudinal
Ligamentum flavum (elastic)
PLL diverts herniation posteriolaterally
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Posterior Structures (Elements) of Motion Segment

• Pedicles and lamina form the neural arch.
• Facet joints between the superior and inferior
  articulating surfaces.
• Transverse and spinous processes.
• Interspinous and supraspinous ligaments.
• Ligamentum lavum.
• Intervertebral foramina.

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Facet Joint

• Articulation between the superior (concave) and
  inferior (convex) facets.
• Guide intervertebral motion through their
  orientation in the transverse and frontal planes.

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Facet Joint Capsule

• Limit motions.
• Strongest in thoracolumbar and cervicothoracic
  regions where the curvatures change.
• Resist flexion and undertake tensile loading in
  the superior portion with axial loading or
  extension.
• Resists rotation in lumbar region.

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Intervebral Foramina

• Exit for nerve root.
• The size is dictated by the disc heights and the
  pedicle shape.
• Will lose space with osteophytic formation,
  hypertrophy of ligaments and loss of disc height
  with aging lateral stenosis.
• Decreases by 20 with extension and increases 24
  with flexion

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Spinal Stability

• The columns ability to react to multiple forces
  placed on it.
• Degeneration increases instability.
• Body reacts to restore through fibrosus and
  osteophytic changes.

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Types of Segmental Loading

• Axial Compression
• Bending
• Torsion
• Shear

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Axial Compression

• Caused by gravity, ground reaction forces, muscle
  contraction and ligaments reaction to tensile
  forces.
• Intradiscal loads can range from 294N to 3332N
  depending upon position.
• Most load in anterior segment, posterior can load
  from 0-30 depending upon segments position.
• Compression at the disk causes tension at the
  annulus, changing the angle of the fibers and
  increasing the stability.

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Axial Compression (contd)

• Creep will occur in the disc, will be larger with
  increased force and aging.
• 5-11 of H2O is lost through creep.
• Creep is rapid 1.5-2mm in 10 min.
• Plateaus at 90 minutes.

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Bending

• Combination of compression, shear and tensile
  forces on the segment from translation.
• Bending into flexion will be resisted by
  posterior annulus, PLL and the facet capsule and
  anterior compressive forces on the anterior
  structures causing disc displacement.
• For extension posterior compressive forces in
  anterior segment and there is a tensile load in
  facet capsule and ALL.

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Torsion

• Caused by axial rotation and coupled motions.
• Stiffness may increase due to facet compression
  with certain motions i.e., flexion increases
  torsional stiffness at L3-4.
• Annulus fibrosus resists, 1/2 fibers CW other 1/2
  CCW facets may help depending upon the
  orientation (resists in a tensile manner).
• When combined with flexion the amount of force
  required for tissue failure is decreased.

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Shear

• Facet joint resists especially in the lumbar
  area.
• Annulus will undergo some tensile forces
  depending upon direction and the fiber
  orientation or angle.
• Discs also resist but if creep occurs - the facet
  may undergo more loading.

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Mobility

• Amount and direct of motion in a segment is
  determined by
• Vertebral body/disc size.
• Facet orientation frontal vs. sagittal.

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Flexion

• Superior vertebra will anterior tilt and forward
  gliding will occur
• Widening the intervertebral foramina 24.
• Adds compressive forces on the anterior aspect
  of the anterior segment moving the nucleus
  pulposus posteriorly.
• Tensile forces placed on posterior annulus,
  flavum, capsule and PLL.
• Central canal is widened
• Rationale for some of Williams flexion exercises

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Extension

• Superior vertebra will tilt and glide posteriorly
  and the intervertebral foramina narrowed up to
  20.
• The central canal is also narrowed.
• Nucleus pulposus moves anteriorly

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Lateral Flexion

• Superior vertebra will translate, tilt and rotate
  over inferior - direction will differ.
• Concavity towards, convexity opposite
• Tensile forces on convexity, compressive forces
  on concavity
• Extension in ipsilateral facet.
• Flexion in contralateral facet.

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Rotation

• Accessory motions are like lateral flexion due to
  same coupling in cervical and upper thoracic
  spine.
• Exception with lower T/S and L/S in neutral
  coupling then opposite (in most references).
• If the motion segment is flexed or extended spine
  (in most references) the coupling will be the
  same.

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Regional Structural andFunctional Differences

• Differences are apparent due to connection
  requirements, sacral, upper C-spine, all
  junctions
• Vertebral body size increases with support
  requirements.
• Cervical, thoracic,lumbar, and sacral/cocygeal.

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Cervical

• CO - occipital
• C1 - Atlas
• C2 - Axis
• C3-6 - general basic structure

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Cervical Region Function

• Mobility gt Stability.
• Upper cervical unit C0-2
• Lower Cervical unit
• C2-7

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C0-1

• C0 occiput containing the occipital condyle
  convex.
• C1 - no body, disk and spinous process allows for
  free space and a large neutral zone and cord
  protection - this means more motion.
• Lateral facets of CO on C1 - concave C1 on convex
  CO - flex/ext or nodding and minimal to no
  lateral flexion/rotation.

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C1-2
Dens

• 2 facets laterally and 1 medially with dens and
  anterior arch
• transverse ligament helps control (C1 on C2
  anterior displacement), stabilizes allows
  nodding
• also provides cartilaginous surface as does the
  alar ligament - limits flex/ext so right rotation
  requires left lateral facet to slide anterior and
  right lateral facet to slide posterior so
  rotation is coupled with extension.
• Can account for up to 50 of rotation in the neck
  and most of the initial ROM.

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C2-7

• 50 wider than they are deep.
• Transverse process holds foramen for vertebral
  artery, vein and plexus, and grove for the spinal
  nerve.
• Facet orientation is roughly 45 degrees(35-65) in
  the transverse plane w/ loose capsule - allows
  for motion in all planes and more rotation and
  lateral flexion than other regions.

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Thoracic Spine Function

• Articulation for the ribs
• Least mobility
• Increasing load bearing
• Lat flex flex/Ext

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Thoracic Spine Body

• T1 - similar to cervical in (C7a).
• Normally the vertebral body equals width and
  depth.
• The ratio of disc diameter to height is highest.
  This will
• Decrease tensile forces
• Decrease possibility of disc injury
• Posterior aspect becomes thicker as you go lower
  - ribs bigger (articulates) and more compressive
  forces.
• End-plates become larger (higher compressive
  forces) as you go caudally.

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Thoracic Spine

• Less flexible due to rib articulation, smaller
  disc to body ratio, spinous process.
• Flavum and ALL are thicker facet capsule less
  flexible.
• Upper thoracic spine facet orientation
• Limits flexion extension - 60/20 transv/front
• Allows coupled lat/rot. (rot of spinous process
  to the convex side)
• Facets are more sagittal in T9-12 to allow
  flex/ext and rot of spinous process will be
  toward concavity (lumbar coupling).

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Thoracic Spine

• Rib articulation consists of 2 articulations to
  the thoracic vertebra
• Anterior surface of the lateral process
• Lateral aspect of the vertebral body.
• Bucket handle motion of the ribs with breathing.
• Extension and contralateral lateral flexion ribs
  separate.
• Flexion and lateral flexion ipsilaterally
  compresses ribs.

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Thoracic Spine

• Scoliosis will cause a rib hump.
• Combination of tranverse plane rotation and
  frontal plane sidebend contralateral coupling.
• Convex side will occur on the ipsilateral rotated
  side causing hump.

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Lumbar Spine

• Most load bearing structures in the skeletal
  system
• Sagittal plane motion
• Largest body/disc, lamina and pedicles short and
  thick for load bearing.

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Lumbar Spine

• L5 transitional, wedge shape of body and disc
  Anterior gt posterior.
• L5-S1 most flexion extension.
• Coupling of motion - right lateral flexion will
  result in right sidebend and left rotation of
  vertebral body (when L/S in neutral)

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Spinal Musculature

• Mobility vs. Stability
• Slow twitch SO vs. fast twitch FOG
• Energy storage
• Consider the line-of-pull of all spinal muscles

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Spinal Muscles
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Common Theme
Small angle of insertion Therefore
Rotary component
Compressive component
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Common Theme
Small angle of insertion Therefore
Rotary component
Compressive component
When are active vs. passive exercised indicated?
When are they not?
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Hip Flexors Abdominals
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General Comment Regarding Function

• Contracture vs. contraction

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General Comment Regarding Function

• Contracture of hip flexors and effect on lumbar
  spine

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General Comment Regarding Function

• Abdominals
• Pelvic stability/balance
• Guy-support system

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