Spine Kinesiology Part 1

Spine Functions

1. Shock absorption

2. Rigid column

3. Attachment for muscles & ligaments

4. Protect spinal cord

5. Supports the thorax

Spinal Vertebrae

• 7 cervical

• 12 thoracic

• 5 lumbar

• 5 sacral (fused)

• 4 coccygeal (fused)

Spinal Curves

Lordotic, kyphotic, and compensatory curves that provide flexibility, balance, and support to the spine.

• Cervical lordosis

• Thoracic kyphosis

• Lumbar lordosis

• Sacrococcygeal kyphosis

Lordosis

Projecting anterior, inward facing curve, anterior direction for convexity in the lumbar and cervical regions of the spine.

Kyphosis

Projecting posterior, outward facing curve, posterior direction for convexity. This curve is prominent in the thoracic and sacral regions of the spine.

Scoliosis

A lateral curvature of the spine that can occur in the thoracic, lumbar, or sacral regions, often presenting as a C or S shape.

Normal spinal curves develop as ____ posture is assumed.

Upright

Cervical Spine Development

By age 3 months

Lumbar Spine Development

Complete by age 10

True or False: Spinal curves are static.

FALSE; a change in one curve is compensated by a change in another curve.

Types of Faulty Posture

Angle of Pelvic Inclination (Pelvic Tilt)

What effect does an anterior pelvic tilt have on the lumbar spine curvature?

Increased lordotic curve

What effect does a posterior pelvic tilt have on the lumbar spine curvature?

Decreased lordotic curve (flattens the back- “flat back”)

Spinal Weight-Bearing

Vertebral body/disc and facet joints

Vertebral Body/Disc

• Want evenly distributed load on disc

• Most important in lumbar spine; bear approximately 80% of weight

Facet Joints

• Bear approximately 20% of weight

• Relative load on facet vs. disc depends on spinal curvature and habitual motions

Extreme extension and increased lordotic curve= an increased load on what type of joint?

Facet jointand increased stress on the lumbar spine.

Extreme flexion= an increased load on what?

Vertebral Body/Disc (Loading Rate= 90/10)

Neural/Vertebral Arch

• Transverse processes (2)

• Spinous process

• Pedicles (2) (connect arch to vertebral body)

• Lamina (2) (spinous to transverse process)

• Articular facets (4)

  • 2 superior, 2 inferior

  • Facet joints or Zygapophyseal or Apophyseal joints

C-Spine Spinous Processes

C2 first prominent, then C6 & C7 (typically bifid in C-spine)

T-Spine Spinous Processes

Shingle effect

L-Spine Spinous Processes

Thick, flat SP

Spinal Flexion and SP

Increase space between SP

Spinal Extension and SP

Decrease space between SP

Transverse Processes

• Serve as “outriggers” for attachments of muscles

• C1 prominent (only 1 in C-spine)

  • Transverse foramen for Vertebral Artery

• T1-T12 TP’s prominent– articulate with the ribs

• Mid-thoracic TP: at Sp level of superior segment

• L1-L5: TP very prominent (1” from SP)

Vertebral Bodies

• Primary weight-bearing site spine

• Increased thickness from C-spine to L-spine

• C3-C7 Uncinate Processes: on superior aspect of vertebral body

Spinal Segment

• Consists of two adjacent spinal vertebrae and the articulations that joint them together (L4-L5, T5-T6, C6-C7, etc…)

• All spine motion: top segment moves on the bottom

• Segments between 2 regions of the spine are called “transitional” segments (T12-L1, L5-S1)

If patients perform extension, how does Intervertebral Foramen (IVF) size change?

Decrease

If patients perform flexion, how does Intervertebral Foramen (IVF) size change?

Increase

“Mixed” Nerve Root Exits at IVF

• Mixed nerve root has both sensory & motor fibers

• Dorsal (afferent) carries sensory info

• Ventral (efferent) carries motor info & both combine to form mixed nerve root which exits at IVF

Intervertebral Disc

One between each 2 adjacent vertebrae, C2-S1

(Zyg)Apophyseal (Facet) Joints

2 between each 2 adjacent vertebrae (R&L)

“Special”/Atypical Joints

• Occiput-C1 (Atlantooccipital or AO joint)

• C1-C2 (Atlantoaxial or AA joint)

• Uncovertebral: Typically C3-C7

• Rib articulations

• Pelvis: sacrum articulates with the ilium bone (SI joint)

Zygapophyseal (Facet) Joints

• Synovial joint

• Planar joint surfaces that slide rather than roll

• Guide intervertebral motion based on orientation direction

Facet Joint Orientation: C2-S1

Facets are planar joints that glide rather than roll/slide. Primary direction of glide depends on facet joint orientation.

• C2-C7: 45º from post-inf to ant-sup

• T-spine: frontal plane, provides 1º side bending

• L-spine: sagittal plane, provides 1º flex/ext

• Transitional spine segments: C7-T1, T12-L1, L5-S1

Facet Joint Orientation: Upper Cervical Spine is Unique

• C0-C1: occiput convex, C1 concave

• C1-C2: horizontal, thus rotation most prominent motion here!

Intervertebral Discs

• Increased thickness from cervical to lumbar spine

  • Increased disc thickness allows more motion per segment

• Nerve roots exit adjacent to disc via intervertebral foramen

  • C-spine roots exit above vertebrae

  • L-spine roots exit below vertebrae

Intervertebral Discs and Water

• Approximately 80% water in lumbar spine disc vs. less water % in C-spine discs

  • Disc herniation more common in L-spine– more fibrous in C-spine, so less disc herniations

• Discs make up 25% of spine length

Why do we get shorter as we age or during the course of a day?

OUr discs dry out and we lose height ever so slightly. Overnight, our discs can rehydrate. Reduced load at night. Compression of our spine is greatly reduced.

Intervertebral Disc Functions

• Absorb shock

• Disperse stress

• Bind vertebra together

• Contribute to the spinal curves

• Allow movement (along with facet joint)

Stress Dispersion and Spinal Movement: Pascal’s Law

• Pressure applied to a liquid is dispersed equally in all directions

  • Vertical load is distributed outward against disc annulus

Spine Ligaments: Anterior Longitudinal Ligament (ALL)

• ALL runs along anterior vertebral body from C2-sacrum

• Limits extension

• Thicker and stronger than PLL (2x), thus minimizes anterior disc herniations

• Narrow in C-spine & wider in L-spine

Spine Ligaments: Posterior Longitudinal Ligament (PLL)

• PLL runs along posterior vertebral bodies from C2-sacrum

• Limits flexion of spine

• Thick/wide in C-spine– less posterior disc herniations in C-spine

• Narrow in L-spine– allows more posterior disc herniations in L-spine

Ligamentum Flavum

• Connect lamina to lamina from C2-sacrum, limits flexion

Supraspinous & Interspinous Ligament

• Run between spinous processes; limit flexion

Spine Ligaments Relative to Spinal Cord

Spinal Cord in Central Canal

Thoracolumbar Fascia

• Non-contractile connective tissue

• Plays role in stabilizing lumbar spine (and SI joint) due to connections to spine, erector spinae, QL, gluteus max, latissimus, and abdominals