The Spinal Column

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The Spinal Column

                                                                                                             2004 Huei-Ming Chai          All Right Reserved

Objectives： After studying this topic, the students will be able to

1. to identify the structures of spinal column, including joint type, articular shape, and the surrounding tissues
2. to describe joint motions occurring at the spine, including osteokinematic and arthrokinematic movements, muscle actions, and factors checking hip motions
3. to understand the stability mechanism of the spine and the possible mechanisms of injury
4. to identify the malalignment of the spine in different cardinal planes
5. to understand structure and functions of the intervertebral disc and its shock attenuation ability

1. Neumann DA (2002).  Axial Skeleton： Osteology and Arthrology.  In Neumann DA: Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation. Philadelphia: Mosby.  Chapter 9, pp. 251-303.
2. Neumann DA (2002).  Axial Skeleton：Muscle and joint interaction.  In Neumann DA: Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation. Philadelphia: Mosby.  Chapter 10, pp. 311-351.
3. Smith LK, Weiss EL, Don Lehmkuhl L (1996). Brunnstrom's Clinical Kinesiology, 5th ed.  Philadelphia, F.A. Davis.  Chapter 11, pp. 363-400.
4. Nordin M & Weiner SS (2001).  Biomechanics of the lumbar spine.   In Nordin M & Frankel VH: Basic Biomechanics of the Musculoskeletal System.  Philadelphia: Lippincott Williams & Wilkins. Chapter 10, pp.256-285.
5. Moskovich R (2001).  Biomechanics of the cervical spine.   In Nordin M & Frankel VH: Basic Biomechanics of the Musculoskeletal System.  Philadelphia: Lippincott Williams & Wilkins. Chapter 11, pp.286-317.

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Functions of the Spinal Column

to provide stability and maintain an erect posture

to allow mobility of the head, neck, and trunk in space

to support and transmit loads from the upper body to the pelvis

to absorb the shock

to protect spinal cord

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Joint Structure of the Spine

Components of the Spinal Column

bony structure： 32-33 vertebrae

7 cervical vertebrae

12 thoracic vertebrae

5 lumbar vertebrae

5 fused sacral vertebrae: sacrum

3-4 coccyx

joint structure

lumbar area

facet joint (apophyseal or zygapophyseal joint)

intervertebral joint： fibrocartilage joint

thoracic area

facet joint (apophyseal or zygapophyseal joint)

intervertebral joint： fibrocartilage joint

cervical area

facet joint (apophyseal or zygapophyseal joint)

intervertebral joint： fibrocartilage joint

uncovertebral joint (joint of von Luschka)： fibrocartilage joint

atlanto-occipital (AO) joint

atlantoaxial (AA) joint

anterior atlantoaxial joint

Spinal Curvature

At birth, the spinal column is convex backward (kyphosis) development of 3 physiological spinal curves cervical lordosis： as head raised  from the prone position thoracic kyphosis： at birth lumbar lordosis： as standing up functions to absorb the ground reaction forces to transmit the load of the upper body to the lower extremities

Motion Segment： function unit of the spine

consisting of 2 vertebrae and their intervening soft tissues dividing into 2 columns (anterior and posterior) or 3 columns (anterior, middle, and posterior)
anterior column vertebral body intervertebral disc (IVD) uncinate process intervertebral joint uncovertebral joint anterior atlantoaxial joint posterior column middle column intervertebral foramen pars interarticularis superior articular facet inferior articular facet transverse process facet joint atlanto-occipital joint atlanto-axial joint posterior column lamima spinous process

Facet Joint (Apophyseal Joint, Zygapophyseal Joint)

synovial joint components plane inferior articular process of the upper vertebra plane superior articular process of the lower vertebra joint type： plane 6-direction motions when moving together flexion/ extension sidebending to the left / right rotation to the left/ right arthrokinematic movements anterior glide with flexion posterior glide with extension closed-packed position： maximum extension special form atlanto-occipital joint atlanto-axial joint

Joint

Orientation of Facet Joints

AO joint： anterior, inferior, and medial

AA Joint： nearly horizontal

C2-C7： 20-45º from transverse plane and nearly in frontal plane

thoracic: 45-60º from transverse plane and 20º posterior to frontal plane

lumbar: 90º from transverse plane and 45º posterior to frontal plane

Intervertebral Joint

fibrocartilage structure annulus fibrosus nucleus pulposus end plate functions to bear and distribute loads to restrain excessive motions to allow slight motions motions flexion nucleus pulposus moving posterior anterior fibers compressed posterior fibers stretched extension nucleus pulposus moving anterior anterior fibers stretched posterior fibers compressed rotation nucleus pulposus to opposite annular fibers under shear stress

Occipito-Atlantal Joint (OA Joint) or Atlanto-Occipital Joint (AO joint)

proximal component： concave superior facet of atlas distal component： convex occipital condyle axis： through the centers of both condyles osteokinematic motions head flexion (nodding) head extension slight sidebending with rotation to the opposite side accessory movements anterior glide with head extension posterior glide with head flexion

Joint
Facet Joint

Atlanto-Axial Joint (AA Joint)

proximal component： convex superior facet of axis

distal component： convex inferior facet of atlas

osteokinematic motions： head rotation

Anterior Atlanto-Axial Joint

synovial joint anterior transverse ligament motion： slight flexion/ extension/ rotation

Joint
Facet Joint

Uncovertebral Joint (Joint of von Luschka)

fibrocartilage

structure

unciform process, uncinate process, semilunate process, neurocentral lip

posterolateral edge of the superior rim projects upwards to articulate with the body above

antero-inferior margin of the body projects downwards

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Kinematics of the Spine

Coupled Motions Between Sidebending and Rotation

sidebending with ipsilateral Rot (Lysell, 1969)

ipsilateral facets glide down and backward (extension)

contralateral facets glide up and forward (flexion)

axis： close to ipsilateral facet

compensatory derotation at AA joint for pure horizontal plane motion

compensatory sidebending at AO joint for pure frontal plane motion

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Muscles Around the Spine

Muscles for Trunk Flexion

abdominal muscles

rectus abdominis

obliquus externus abdominis

obliquus internus abdominis

transverse abdominis

Muscles for Trunk Extension

erector spinae

deep layer muscles

multifidus

rotator

interspinalis

intertransversarii

Muscles for Trunk Sidebending

anterior and posterior muscles at the same side contract together

Muscles for Trunk Rotation

ipsilateral obliquus internus abdominis

contralateral obliquus externus abdominis

multifidus

Muscles for Neck Flexion

Sternocleidomatoid flexes lower cervical but need assistance of flattening cervical lordosis from

longus capitis

rectus capitis anterior

rectus capitus lateralis

supra- and infra-hyoid muscles

Muscles for Head Extension

suboccipital muscles rectus capitis posterior major rectus capitis posterior minor obliquus capitis superior obliquus capitis inferior

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Spine Stability

Factors Affecting Stability of the Spine

ligaments anterior longitudinal ligament (ALL) posterior longitudinal ligament (PLL) ligamnetum of flavum intersoinous ligament muscles： dynamic

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Mechanism of Injury at the Spine

Repeated Stress

herniation of intetvertebral disc nucleus pulposus shifts to posterior during spinal flexion posterior fibers under tension posterior longitudinal ligament narrow at lumbar spine
osteoarthrosis usually appear at the uncovertebral and/or facet joints
spondylolithesis fracture or bone defect occurs at the pars interarticularis due to prolonged stress on the posterior column of the lumbar spine increase lumbar lordosis and then sacral angle

Malalignment

forward head (turtle neck)

hyperflexion of lower cervical spine

hyperextension of upper cervical spine