Intrinsic back muscles + functional anatomy of the spine

Week 5

vertebral column composition

Articulating vertebrae: 24

• Cervical: 7

• Thoracic: 12

• Lumbar: 5

Fused: 8-10

• Sacrum: 5

• Coccyx: 3 – 5 (fused)

Total: 32 – 34 vertebrae

four spine curves

Primary Curvature (Kyphotic): present during foetal development, concave anteriorly

• thoracic

• sacral

Secondary Curvature (Lordotic): forms after birth, concave posteriorly

• cervical: develops when a baby can hold up its head

• lumbar: develops when a baby stands up

movements of the back

1. passive movement

2. active movement

3. cervical

4. thoracic

5. lumbar

6. bilateral contraction

7. ipsilateral contraction

8. contralateral contraction

passive movement

• movement occurring without active muscle contraction

• due to gravity acting on the body's mass

active movement

muscles of the back

• extend

• laterally flex

• rotate

cervical trunk movement

• flexion and extension

• lateral flexion

• rotation

thoracic trunk movement

• lateral flexion

• rotation

lumbar trunk movement

• flexion/extension

• (very limited rotation)

bilateral contraction trunk movement

• extension

ipsilateral contraction trunk movement

• lateral flexion and rotation

contralateral contraction trunk movement

• lateral flexion and rotation

extrinsic muscles of back role

move upper limbs and ribs

intrinsic muscles of back role

• maintain posture

• move the vertebral column

• innervated by posterior rami of spinal nerves: proprioception

5 categories of back pain (conditions)

1. traumatic

2. degenerative

3. inflammatory

4. oncologic

5. infectious

traumatic back pain

• injury to:

  • spine

  • intervertebral discs (IVD)

  • soft tissues

• acute lower back pain = lumbago

  • pain/strain to quadratus lumborum

    or

  • paraspinal muscles/IVD herniation

degenerative back pain

• MSK structures weaken

• causes:

  • aging

  • overuse

  • pre-existing pathology (e.g. disc herniation)

inflammatory back pain

• infection of malignancy

• e.g. ankylosing spondylitis and sacroiliitis

oncologic back pain

• caused by cancer or its treatment":

  • pathologic fractures (bone weakened e.g. due to cancer)

  • lytic lesions to the spine (areas of bone destruction causing holes in the bone)

  • cancers of the marrow

infectious back pain

• from direct inoculation (IV drugs, spinal procedures e.g. lumbar puncture) or another source

• infections can occur:

  • spine

  • discs

  • soft tissue (forming abscesses)

source of back pain

lower back muscles

back muscles causing headaches

upper back muscles

movement with high risk of back muscle damage

eccentric contraction

back muscles proprioception

• back muscles are mainly proprioceptive

• mostly provide sensory information about the position & movement of the spine

• contributes significantly to its postural stability and fine control

thoracolumbar fascia

• sheet of connective tissue that runs along the lower back

• separates paraspinal muscles and the posterior abdominal wall muscles (quadratus lumborum, and psoas major)

vertebral body

weight bearing

lamina

connects spinous and transverse processes

pedicle

bony pillars attaching arch to body

spinous process

superior articular facet

superior articular process

transverse process

lateral/posterior projection

vertebral arch

vertebral foramen (spinal canal)

inferior articular facet

inferior articular process

spinous process

posterior projection

superior articular process

transverse process

lateral/posterior projection

atlas vertebra

• C1 (cervical 1)

• no vertebral body

• no spinous process

• has a vertebral foramen for vertebral artery

anterior arch (C1)

anterior tubercle (C1)

articular facet for dens (C1)

lateral mass

posterior arch (C1)

posterior tubercle (C1)

superior articular surface of lateral mass for occipital condyle (C1)

transverse foramen (C1)

transverse process (C1)

vertebral foramen (C1)

axis vertebra

• C2 (cervical 2)

• Extended vertebral body

  • Odontoid process (Dens) extends superiorly

• Articulates with atlas

  • Atlantoaxial joint

• Provides an axis (pivot) for atlas

• No intervertebral disc between C1 & C2

anterior articular facet (C2)

vertebral body (C2)

dens (C2)

inferior articular facet (C2)

inferior articular process (C2)

interarticular part (C2)

pedicle (C2)

posterior articular facet (C2)

spinous process (C2)

superior articular facet (C2)

transverse process (C2)

cervical vertebrae (C3-C7)

• Transverse foramina (for vertebral arteries)

• Large triangular vertebral foramen

• Bifid spinous process

• Exception: C7 single prominent spinous process (vertebra prominens)

transverse foramen

characteristic of cervical vertebrae

bifid spinous process

characteristic of cervical vertebrae (except C7)

thoracic vertebrae

• T1-T12

•  heart-shaped vertebral body & rounded vertebral foramen

• Costal Facets: on body or transverse processes, articulate with tubercles of the ribs

• Demi-facets: articulate with heads of the ribs (ribs 2-9)

• Spinous processes:

  • long and slant inferiorly

  • Increase protection to spinal cord

  • Prevents objects from entering spinal canal

vertebral body (thoracic)

inferior articular process (thoracic)

inferior demi-facet (thoracic)

inferior vertebral notch (thoracic)

lamina (thoracic)

pedicle (thoracic)

spinous process (thoracic)

superior articular process and facet (thoracic)

superior demi-facet (thoracic)

superior vertebral notch (thoracic)

transverse costal facet (thoracic)

transverse process (thoracic)

vertebral foramen (thoracic)

lumbar vertebrae

• L1-L5

• Large, kidney-shaped vertebral body

• Short, wide spinous processes

• Long, thin transverse processes (except L5)

• Vertebral foramen: triangular

• Sup / Inf artic. processes face inwards/outwards

• NO transverse foramina

vertebral body (lumbar)

inferior articular process (lumbar)

lamina (lumbar)

pedicle (lumbar)

spinous process (lumbar)

superior articular surface (lumbar)

transverse process (lumbar)

vertebral foramen (lumbar)

Zygapophyseal/facet joints

• Synovial joints between sup/inf articular processes

• allow for gliding movements

• type of movement determined by its shape & arrangement

• Provide strength to vertebral column, allow gliding movements & flexibility

Zygapophyseal/facet joint types

1. cervical facet joints

2. thoracic facet joints

3. lumbar facet joints

cervical facet/zygapophyseal joints

Transverse plane - slope inferior to posterior (45º)

Flexion / Extension = loose and more mobile

cervical region movements

• flexion and extension

• lateral flexion

• rotation

lumbar facet/zygapophyseal joints

Sagittal plane - face medially (superior) and laterally (inferior)

Flexion / Extension

lumbar region movements

• flexion

• extension

• (minimal rotation)

thoracic facet/zygapophyseal joints

Coronal plane - slope almost vertical (60º)

Limited movement

thoracic region movements

• rotation

• lateral flexion

• (very limited flexion and extension)

Anulus Fibrosus

• Allows intervertebral discs to withstand compression

• Thick, tough, strong radial tire–like structure made up of lamellae

• Concentric sheets of collagen fibres connected to vertebral end plates at various angles

• Encloses the nucleus pulposus

nucleus pulposus

• Provides flexibility and resilience to the IVD

• Gelatinous core, avascular

  • receives blood supply via diffusion of anulus fibrosus

• Mostly H₂O +  primarily type II collagen & proteoglycans

intervertebral disc function

• Allows movement between adjacent vertebral bodies

• Absorbs shock & transmits load

• Accounts for flexibility of vertebral column

anulus fibrosus

intervertebral foramen