Axial Skeleton - Osteology & Arthrology

Normal curvature: cervical spine

30-35 lordosis

Normal curvature: thoracic spine

40 kyphosis

Normal curvature: lumbar spine

45 lordosis

Normal curvature: sacrococcygeal

Kyphosis

What is the function of normal, dynamic curvatures of the vertebral column?

Provide strength and resilience

Full extension _______ (increases/decreases) cervical and lumbar lordosis but ____________ (increases/decreases) thoracic kypohosis

Increases, decreases (reduces)

Flexion ________ (increases/decreases) cervical and lumbar lordosis but __________ (increases/decreases) thoracic kyphosis

Decreases, increases

An "ideal" line of gravity passes where in relation to: mastoid process of temporal bone

Through

An "ideal" line of gravity passes where in relation to: S2 vertebra

Just anterior

An "ideal" line of gravity passes where in relation to: hip joints

Just posterior

An "ideal" line of gravity passes where in relation to: knee and ankle

Anterior

An "ideal" line of gravity passes where in relation to: apex of each curvature

Just to concave side of apex

In relation to the force of gravity, what is another benefit of our spinal curvatures?

Force of gravity produces torques in alternating flexion and extension directions --> minimizing total net external torque

Which 4 factors determine the shape of spinal curves?

1. IV discs & bodies

2. Orientation of facet joints

3. Composition of ligaments

4. Degree of natural muscle stiffness

When severe, abnormal vertebral curvatures _________ (increase/decrease) stress on muscles, ligs, bones, IV discs, apophyseal joints, spinal nerve roots, & ability to expand diaphragm

Increase

_________: normal curvatures w/ ant pelvic tilt

"Ideal" posture

_________: exaggerated thoracic kyphosis and lumbar lordosis

"Swayback"

_________: reduced curvatures

"Flat back"

_________: increased thoracic kyphosis and reduced lumbar lordosis

"Rounded back"

Ligamentum flavum limits _________

Flexion

Supraspinous and interspinous ligaments limit _______

Flexion

Intertransverse ligaments limit ________

Contralateral lateral flexion & flexion

Posterior longitudinal ligament limits _________ and reinforces _________

Flexion, posterior disc

Anterior longitudinal ligament limits _________

Extension, excessive lordosis

Apophyseal joint capsules strengthen __________

Apophyseal joints

True or false: ligamentum flavum is highly elastic

True!! (80% elastin)

B/w neutral and full flexion, the ligamentum flavum elongates an additional __________%

35% (in total, this places the ligament on 50% strain)

True or false: the ligamentum flavum provides constant & moderate resistance to flexion throughout the range

True!! (in fact, it is already strained 15% at neutral)

What are the 3 functional components of a typical IV junction?

1. TPs & SPs

2. Apophyseal joints

3. Interbody joints

________: function as mechanical levers that increase leverage of muscles and ligaments

TPs & SPs

________: guide intervertebral motion

Apophyseal joints

_________: absorb and distribute loads, allow one vertebral body to "rock" on another; approximate axis of rotation

Interbody joint

80% of load goes through which structure in the spine?

Interbody joint

__________: central get w/ high water content to absorb shock and transfer loads

Nucleus pulposus

_______: rings of collagen fibers providing strength and flexibility

Annulus fibrosus

________: thin cartilaginous caps covering vertebral body made of fibrocartilage (facing disc) and calcified cartilage (facing bone)

Vertebral end plate

How does the IV disc receive nutrients?

Diffusion via endplates

NOTE: as we age, increased calcification limits nutrients & O2 which compromises discs ability to absorb loads

Why are the collagen fibers of the annulus fibrosus angled at 65 from vertical (otherwise known as 25 from horizontal)?

Permits tensile forces in 4/6 movements that we do

What is the downside of the collagen fibers of the annulus fibrosus only being 25 from the horizontal?

More susceptible to torsional forces

Briefly explain how the IV discs distribute pressure.

Compression force from BW & muscle contraction raises hydrostatic pressure in nucleus pulposus --> elevates tension in annulus fibrosis to inhibit expansion --> pressure evenly redistributed to several tissues

Which structure prevents migration of the disc material?

Posterior annulus

If a disc has a weak, cracked or distend posterior annulus, what pathology may occur?

Herniated nucleus pulposus

True or false: disc protrusions or bulges are common in asymptomatic individuals -- extrusions are not

TRUE

What is the difference b/w a protrusion and extrusion?

The main difference between a protrusion and an extrusion is that the nucleus has broken out of the wall of the annulus with an extrusion. A protrusion can lead to an extrusion if the nucleus pushes hard enough and the annulus wall gives out.

If nuclear material impinges on spinal cord or nerve roots, what symptoms might a patient present with?

Pain, altered sensation, muscle weakness and reduced reflexes based on motor & sensory distribution of impinged nerve roots

Sustained lumbar _______ (extension/flexion) reduces pressure in the disc (thereby allowing water to swell the disc)

Extension

What time of day are we tallest? Why?

Waking -- due to the water-retaining capacity of the discs while we sleep

Which position causes the highest disc pressure? Why?

Lifting 20 kg, bent over w/ round back -- flexion (especially with loads) puts higher load on disc

Movement throughout the vertebral column is described as ______________: direction of movement on ________ side of ________ vertebral segment

Cranial-to-caudal, anterior, superior

Type: apophyseal joints

Plane

Apophyseal joints are near _________ in lower thoracic, lumbar and lumbosacral regions to block excessive translation to maintain space for spinal cord and spinal nerve roots

Vertical

__________ facets favor axial rotation

Horizontal

___________ facets block axial rotation

Vertical

_________: articular facet surface moves closer to its partner facet, usually caused by a compressive force

Approximation

__________: articular facet surface moves away from its partner facet, usually caused by a distraction force

Separation (gapping)

________: articular facet translates in linear or curvilinear direction relative to another, caused by a force directed tangential to the joint surface

Sliding (gliding)

Superior articular facet position: cervical

Posterior & superior

Superior articular facet position: thoracic

Mostly posterior

Superior articular facet position: lumbar

Medial to posterior-medial

AO joint: articulation

Convex condyles of occipital bone on concave superior articular facets of the atlas

AO joint: DOF

2 -- flexion/extension, slight lateral flexion

Which motion does the AO joint NOT have?

Rotation

AO joint: ligamentous stability

Alar ligament from dens --> occipital condyle (limits axial rotation)

AA joint: articulation(s)

Median: dens of axis through osseous ligamentous ring of anterior arch of atlas and transverse ligament

2 apophyseal joints w/ flat orientation

AA joint: DOF

2 -- rotation, limited flexion/extension

Which motion does the AA joint NOT have?

Lateral flexion

Intracervical apophyseal joints (C2-C7): articulation

Facet surfaces oriented like shingles on a 45 degree sloped roof

C2-C7: superior facets face _________ and ___________

Posterior and superior (inferior facets are opp.)

C2-C7: DOF

3 -- flexion/extension, rotation, lateral flexion

Osteokinematics (neck): extension

75-80

Osteokinematics (neck): flexion

45-50

When is the volume of the cervical vertebral canal greatest?

Full flexion (least in full extension)

Arthrokinematics (AO): flexion & extension

Convex occiput rolls POSTERIORLY w/ ANTERIOR slide during extension -- anteriorly w/ posterior slide during flexion

Arthrokinematics (AA): flexion & extension

Tilt for slight flexion/extension

Arthrokinematics (C2-C7): flexion & extension

Extension: inferior facets of cranial vertebrae --> slide inferiorly and posteriorly

Flexion: inferior facets --> slide superiorly and anteriorly

_________: upper cervical extension + lower cervical flexion

Protraction

_________: upper cervical flexion + lower cervical extension

Retraction (double chin)

Osteokinematics (neck): rotation

65-75 degrees each side

How much rotation comes from the AA joint?

50-60%

True or false: the AO joint can rotate

FALSE -- it is negligible

Arthrokinematics (AA): rotation

Ring-shaped atlas "twists" about the dens -- flat inferior facets slide on superior facets

During rotation @ the AA joint, there is a __________ (posterior/anterior) slide on side of rotation & __________ (posterior/anterior) on opposite side

Posterior, anterior

Arthrokinematics (C2-C7): same side as rotation

Inferior facets of cranial vertebrae -- slide posteriorly and slightly inferiorly

Arthrokinematics (C2-C7): opp side of rotation

Inferior facets of cranial vertebrae -- slide anteriorly and slightly superiorly

Osteokinematics (neck): lateral flexion

35-40 degrees each direction

Arthrokinematics (AO): lateral flexion

Small amount of rolling w/ opposite slide

Arthrokinematics (AA): lateral flexion

SIKEEEE - N/A

Arthrokinematics (C2-C7): same side as lateral flexion

Inferior facets of cranial vertebrae -- slide inferiorly and slightly posteriorly

Arthrokinematics (C2-C7): opp side as lateral flexion

Inferior facets of cranial vertebrae -- slide superiorly and slightly anteriorly

How do the facet joints of the thoracic spine differ from the cervical in terms of orientation?

Generally in frontal plane with forward slope (15-25 from vertical)

Superior facets (thoracic): face mostly ________

Posterior

Inferior facets (thoracic): face mostly ________

Anterior

___________ joints: head of rib + costal demi-facets on thoracic vertebral bodies

Costocorporeal (costovertebral)

_________ joints: tubercle of rib + costal facet of TP

Costotransverse

What provides the thoracic spine's mechanical stability?

Rib cage

Osteokinematics (thoracic): flexion & extension

30-40 flexion, 15-20 extension (from neutral kyphosis)

Osteokinematics (thoracic): rotation

25-35

Osteokinematics (thoracic): lateral flexion

25-30

How do the facet joints of the lumbar spine differ from the thoracic & cervical in terms of orientation?

Nearly vertical -- favors sagittal over transverse plane motion

Superior facets (lumbar) face mostly _________

Medial to post-med