Spine Mechanics

You have _ bones in the spinal column, _ discs.

• There are _ cervical, _ thoracic, _ lumbar, _ sacral, _ coccygeal

33, 23

• 7, 12, 5, 5, 4

Forces of the body are carried by the _ _ (70%) and _ _ (30%)

Vertebral body, facet joints

The interbody joint has _ and _ _, with a _ in the middle. The former has _ and _ layers.

Superior and inferior endplates, discs. Bony and hyaline cartilage

Disc height increases _

A greater disc:body ratio means greater _

• Cervical= _

• Thoracic= _

• Lumbar= _

Inferiorly

Mobility

• 2:5

• 1:5

• 1:3

Nucleus pulposus is effective in _, Annulus Fibrosus is effective in _

Compression, Tension

Cervical facets oriented _ degrees _ horizontal, Thoracic is _ and _, Lumbar is at _ plane

45 above, up and out, sagittal

Superior vertebral body’s _ facet interfaces with inferior body’s _ facet

Inferior, superior

Spinal curvature development: thoracic _ → cervical and lumbar _. This helps to resist spinal _

Kyphosis → Lordosis. Compression

Spinal motion is described _ to _

Cranial to caudal

Functional spinal unit is comprised of what?

Two vertebral bodies, 1 disc, intra-articular structures

The axis of rotation for spine is _ _, single-level movement is limited so “_” increases ROM

not fixed, “stacking”

Spine has _ DOF, _ angular and _ translatory

6, 3 and 3

_ structures guide spinal motion, _ drive and control spinal motion

Osteoligamentous, muscles

Main coupling sequence for spinal motion is _ with _.

• In cervical it is _ direction, Lumbar it is _ direction.

Rotation with sidebending

• Same, opposite

For cervical, thoracic, and lumbar in Flexion, facet joints _ _

Glide open

For cervical, thoracic, and lumbar in Extension, facet joints _ _

Glide closed

For cervical, thoracic, and lumbar in Sidebending, ipsilateral facets _  and contralateral facets _

Close, Open

For axial rotation, cervical and upper thoracic regions _. Lower thoracic and lumbar regions either experience _ or _

Glide. Gapping or compression

Axial Rotation!

• C+UT- _

• LT+ L- _

• Ipsilateral facets close, contralateral facets open

• Ipsilateral gapping, contralateral compression

The direction of spinal motion is primarily dictated by the orientation of _

Facets

What structure really limits thoracic motion?

The ribs

Cervical has _ mobility, Thoracic can _/_, Lumbar can _/_ the spine.

All, Rotate/Sidebend, Flex/Extend

Instability is the loss of spinal _, leading to increased movements in the segment

Stiffness

What are the three intersegmental ligaments and what do they restrict?

1. Anterior Longitudinal- Extension + translation

2. Posterior Longitudinal- Flexion + supports annular wall

3. Supraspinous- Flexion + spinous process distraction

What are the four intrasegmental ligaments and what do they restrict?

1. Interspinous- Flexion + sp distraction

2. Ligamentum Flavum- Flexion + assists in standing upright

3. Intertransverse- Bending

4. Facet Capsule- Keeps joint tight

AO joint accounts for _% (30 deg) of cervical F/E, AA joint accounts for _% of cervical axial rotation

20%

50%

Alar ligament connects dens (_ _) to skull, restricting _ of skull on _ _

(C2), sidebending of skull on C1

The Atlantocruciform ligament (_ part) allows for pivoting of _-_, and holds the dens _ (away from brainstem)

(transverse), C1-C2, forward

L5-S1 “sacral slope” limits what two things?

Shear force, fracture

SI joint achieves what motions?

• What ligaments counters these forces?

Nutation (sacrum moving forward on ilium) and counternutation

• Sacrospinous and sacrotuberous

What is the lumbopelvic rhythm?

• In flexion, spine moves before hips

• In extension, hips move before spine

Iliolumbar ligament restricts what?

• Note: Sacroiliac ligament and pubic symphysis should also be aware of

Limits side bending, anterior displacement of L5

You use the _ _ when checking for scoliosis

Cobb angle

Protraction motion is _ of upper 2 joints, _ of lower cervical

• Note: opposite for retraction

Extension, flexion

Spinal muscles are for _ and _

Movement and stability

Intrinsic muscles maintain posture/control of _, Extrinsic muscles attach _ to _, which moves them.

Spine, spine to extremities

General: When trying to figure out spinal motion…

• Superior attachment/origin more lateral than inferior attachment= _ rotation

• Superior attachment more medial than inferior attachment= _ rotation

• Ipsilateral

• Contralateral

List the intrinsic muscles by layer and actions!

• Superficial (2): _

• Intermediate (3): _

• Deep (4): _

Splenius capitis + cervicis

• (B: extension, U: ips SB+R)

Spinalis + Longissimus + Iliocostalis 

• (B: extension, U: ips SB)

Semispinalis + Rotatores + Multifidus+ Intertransversarii

• Semi extends, inter does ips SB, R+M do ips SB and contralateral rotation

Sternocleidomastoid actions are what?

Bilateral flexion

Unilateral: Contralateral rotation, ipsilateral sidebending

Scalenes actions are what?

B: Flexion

U: ips SB

Levator scapulae does what?

Ipsilateral SB + rotation

Upper trapezius?

B: extension

U: ips SB + contralateral rotation

Latissimus dorsi?

B: extension

U: ips SB+ ips rotation

Rhomboids?

B: extension

U: ips SB+ cont rotation

Glute max?

Hip extension

Rectus abdominis?

Flexion

External oblique?

• Flexion, ips SB, cont rotation

Internal oblique?

• Flexion, ips SB, ips rotation

Quadratus lumborum?

Ips SB

You have way more _ musculature to hold you upright

Posterior

_ (coupling patterns) and _ (motion) of spinal movement is important when working with a patient

Quality and quantity

What are the three components of spine stabilization?

Passive stabilization

Active stabilization

Central Nervous control

Typically, you want to be within a small “_ _” on a load-displacement curve for spinal stability. This is achieved by _ activation (_ for stability).

Neutral zone. Muscle (deep)

What muscle can have fatty deposits or atrophy and cause LBP?

Multifidus

The combined action of the abdominal muscles increases _ _ _, contributing to spinal stability

Intra-abdominal pressure (IAP)

Disc injuries are due to NP moving out _ _

Posterior laterally