PHED 386

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PHED 386

• Biomechanics of the Spine

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Todays objectives

• Analyze structure vs. function of the spine
• Identify factors influencing mobility stability
  of regions of the spine
• Identify the relationship between muscle location
  its effectiveness on the trunk
• List mechanical contributions to common injury

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Structure of the spine

• Vertebral column
• Curved stack of 33 vertebrae
• Movements motion segments
• Joints of the movement segment
• Symphysis bodies discs
• Gliding (diarthroses) facet joints

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Structure of the Spine

• Vertebrae
• Body, neural ring, processes
• Processes provide MA for mms
• Body size-function relationship
• Spines facet joint relationship
• Facet joints assist in loading
• Facet joint compression

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Structure of the spine

• Intervertebral discs
• Composition
• Annulus fibrosus collagen bands cross vertically
  at 30 to each other
• Nucleus pulposus 90 water collagen
  proteoglycans
• Function
• Bind vertebrae together
• Allow for movement
• Bear distribute loads

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Structure of the spine

• Mechanics of discs
• Flexion, extension lateral flexion forces
• Rotation forces

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Structure of the spine

• Compression forces
• Water loss sodium /potassium gain
• Results in loss of 2cm of height
• Within first 30 minutes
• Increased volume ? stiffness
• Theory risk of disc injury early in day

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Disc nutrition

• Blood supply to age 8
• Pumping action from position change
• Negative aspect of fixed position
• Affect of injury aging

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Discs and aging

• Reduced water absorption
• Decreased shock absorbing
• Abnormal movements between vertebrae
• Loads assumed by other structures
• Reduced spinal column height
• Postural alterations

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Ligaments of the spine

• Anterior longitudinal ligament
• Posterior longitudinal ligament
• Supraspinous ligament (ligamentum nuchae)
• Short ligaments
• Interspinous
• Intertransverse
• Ligamentum flavum

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Spinal curves

• Primary
• Thoracic sacral
• Secondary
• Cervical lumbar
• Life changes

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Postural mechanical changes

• ?? Wolffs law
• Lordosis
• Associated w/weak abdominal mms anterior tilt
• Causes
• Kyphosis
• Cause (Scheuermanns disease)
• Population/s
• Scoliosis
• Lateral/rotational deformity
• Causes

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Neck
Normal Hypolordotic Military
Kyphotic S-Shaped
Lower Back
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Movements of the spine

• Flexion, extension, hyperextension
• Greatest in cervical lumbar regions
• Lateral flexion rotation
• Greatest in cervical
• Least in lumbar

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Muscles of the spine

• Complex arrangement
• Naming
• Pairs
• Unilaterally or bilaterally

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Muscles of the spine

• Anterior (cervical region)
• Pre-vertebral muscles
• Rectus capitus anterior lateralis
• Longus capitus
• Longus colli
• Hyoid muscles 8 pairs
• Bilateral tension flexion of the head
• Unilateral lateral flexion or rotation

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Muscles of the spine

• Anterior
• Abdominals
• Rectus abdominus
• External obliques
• Internal obliques
• Bilateral tension flex spine, reduce anterior
  tilt
• Unilateral tension lateral flexion, rotaion
• Abdominal wall function

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Muscles of the spine

• Posterior
• Cervical
• Spenius capitus
• Splenius cervicis
• Assisted by smaller/deeper mms
• Thoracic lumbar
• Errector spinae
• Sacrospinalis, semispinalis,
• Spinalis, longissimus, iliocostalis
• Deep spinal mms

Primary extensors
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Muscles of the spine

• Lateral
• Sternocleidomastoid (antagonistic)
• Scalenes
• Lumbar region
• Quadratus lumborum
• Psoas major

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Loads on the spine

• Forces acting on
• Body weight
• Tension in ligaments
• Muscles tension
• Intra-abdominal pressure
• External loads
• Axial loading
• Spinal compression

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Loads on the spine

• Effect of center of gravity
• Role of spinal extensor mms
• Effect of actual forward bending or arm position
• Spinal mms have very small moment arms ? must
  generate large forces
• Increased compression forces on lumbar spine

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Loads on the spine

• Shear forces on spine
• On lumbar spine in standing position
• Increases during flexion hyperextension
• Contributor to disc herniation

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Loads on the spine

• Flexion relaxation phenomenon
• Tension in extensors increases w/flexion
• At full flexion extensor tension disappears
• Flexion torque supported by posterior spinal
  ligaments
• But increased shear from tension in interspinous
  ligaments
• Also increased facet loading

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Loads on the spine

• Lateral flexion and rotation
• Role of movement speed

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Common injuries

• Low back pain
• 75-80 of population
• Second only to common cold
• Most frequent/expensive of workmans comp claims
• More prevalent in males
• Causes
• Children strains sprains
• Adults
• Sitting for prolonged periods/unable to sit at
  all
• Unnatural postures
• Sudden unexpected motions
• Weak abdominal muscles

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Common injuries

• Soft tissue
• Contact or overload
• Spasm response
• Acute fractures
• forceful contraction of mms
• Contact direct or indirect
• Large compressive loads

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Common injuries

• Stress fractures
• Spondylolysis
• Spondylolisthesis
• From repeated axial loading while hyperextended

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Common injuries

• Disc herniations
• Bulging, slipped, ruptured
• Protrusion of pulposus from annulus
• Common locations cervical lumbar