Biomechanics Ch. 9

-Where is flexion/extension greatest in the spine? -Is there a difference in spinal flexion, hip flexion, and anterior pelvic tilt? -When is hyperextension used?

-Cervical and lumbar regions -Yes -swimming strokes, high jump and pole vault, numerous gymnastic skills

What daily activities require the most motion in the cervical region? Lumbar region?

-Cervical: backing up a car -lumbar: picking up object from floor

Where are the changes in discs as a result of injury and age most common?

-L5-S1- most stress

what is/are scoliosis treatments?

-Mild to moderate: may self-correct with time. Appropriate stretching and strengthening exercises -severe: bracing and/or surgery

What happens to ROM with age and to what degree?

-ROM in cervical spine decreases linearly with increasing age, with a loss in passive ROM of about 0.5 degrees per year.

How does the change in size and angulation of vertebrae affect range of motion?

-They limit the range of motion in the different spinal regions

iv. Mechanically, what are the annulus fibrosus and nucleus pulposus? How so? Explain.

-annulus fibrosus acts as a coiled spring whose tension holds the vertebral bodies together against the resistance of the nucleus pulposus, and the nucleus pulposus acts like a ball bearing composed of an incompressible gel. -During flexion and extension, the vertebral bodies roll over the nucleus while the facet joints guide the movements.

what's the atlas?

-atlas: first cervical vertebrae; provides reciprocally shaped receptacle for the condyles of the occiput of the skull. Forms atlantooccipital joint which is extremely stable with flexion and extension permitted only.

3. Tension developed by external obliques... a. If the spine is fixed... 4. Tension developed by internal obliques... a. If the spine is fixed...

-causes rotation of spine toward opposite side -causes pelvic rotation toward same side -causes rotation of spine toward same side -cause pelvic rotation toward opposite side

Where is spinal rotation the greatest?

-cervical region (C1-C2)

Why should one refrain from any one body position too long?

-curtails pumping action and can negatively affect disc health.

Spine shrinkage throughout the day: 1. What happens when the pressure is relieved? 2. Where in the spine does spinal shrinkage happen? 3. What body positions allow rehydration and height increase in the discs?

-discs quickly reabsorb water, and disc volumes and heights are increased -thoracic and lumbar regions -spinal hyperextension in prone position and trunk flexion in the supine position

ii. The posterior thoracic and lumbar region muscle groups are...(3) 1. Bilateral contraction results in... 2. Unilateral contraction results in...

-erector spinae (sacrospinalis), semispinalis, and deep spinal muscles. -extension and hyperextension of the trunk -lateral flexion

Is stress on the discs greater with flexion or rotation? Justify your answer.

-flexion; bending stress is approx. 450 times greater than the twisting stress from the same angle of bending or twisting on the annulus fibers.

What happens throughout the course of a day to one's height? When does the majority of this occur?

-height decreases up to nearly 2 cm throughout course of a day. -During first 30 mins after person gets up in the morning

ligaments that connect vertebrae through spinous processes

-interspinous ligaments

How do injury and age affect the discs, especially the water-absorbing capability?

-irreversibly reduce the water-absorbing capacity of the discs, with concomitant decrease in shock-absorbing capability.

3. The levator scapulae can also contribute to... 4. The 3 scalenes assist with...

-lateral flexion of neck when contracting unilaterally with scapula stabilized. -flexion and lateral flexion of neck, depending on whether tension is bilateral or unilateral

-What is lateral flexion and where is it greatest in the spine? Least?

-lateral flexion: frontal plane mov't away from anatomical position -greatest in cervical region, C4-C5 -least in L5-S1

What is/are the kyphosis treatment(s)? In what special group is this seen?

-mild cases: exercises to strengthen the posterior thoracic muscles -sever cases: bracing or surgical corrections -elderly women with osteoporosis

As a unit, the spine allows what types of movement(s)? In what plane(s)?

-motion in all 3 planes as well as circumduction

i. What are the major anterior muscle groups of the cervical region? (5) 1. Bilateral tension results in... 2. Unilateral tension results in...

-prevertebral muscles: rectus capitis anterior/lateralis, longus capitis/colli, and 8 pairs of hyoid muscles -flexion of head. Hyoid muscles main function is to move hyoid bone during swallowing -lateral flexion of head toward contracting muscles or rotation of head away from contracting muscles, depending on which other muscles are acting as neutralizers

ii. In the lumbar region the major muscles are...(2) 1. Bilateral contraction results in... 2. Unilateral contraction results in...

-quadratus lumborum, psoas major -flexion of lumbar spine -lateral flexion of lumbar spine

ii. What are the main abdominal muscles? (3) 1. Bilateral tension results in... 2. Unilateral tension results in...

-rectus abdominis, external/internal obliques -flexed spine, reduced anterior pelvic tilt -lateral flexion of spine toward tensed muscles

i. The primary cervical extensors are... (2) 1. Bilateral tension results in... 2. Unilateral tension results in...

-splenius cervicis/capitis -cervical extension -lateral flexion or rotation of the head toward the side of contracting muscles

i. Muscles of the lateral aspect include...(5) 1. Bilateral contraction results in... 2. Unilateral contraction results in...

-sternocleidomastoid, levator scapulae, scalenus anterior, posterior, and medius -either flexion of neck or extension of head -lateral flexion to same side or rotation to opposite side

what 3 joints does the motion segment contain?

-symphyses type of amphiarthrodial joint b/w vertebral bodies separated by the intervertebral discs -right and left facet joints between the superior and inferior articular processes are diarthroses of the gliding type that are lined with articular cartilage

What accounts for most of the spine's ability to resist rotational torsion and shear?

-the facet joints and discs, with more than half the contribution from facet joints.

Why do the vertebrae differ?

-the increased surface area of the lumbar vertebrae serves the functional purpose of reducing the amount of stress to which they would otherwise be subjected.

Although all vertebrae share the same basic shape, how do they differ?

-they progressively increase in size from the cervical region down through the lumbar region

What's a motion segment?

-two adjacent vertebrae and the associated soft tissues; functional unit of the spine

How much of the height of the spine is accounted for by IV discs?

1/4

number of vertebrae:

33

what's lordosis? often associated with...(2)

Exaggeration of lumbar curve. Often associated with weakened ab muscles, anterior tilt.

How does the body get nutrients to and waste out of the IV discs?

Intermittent changes in posture and body position alter internal disc pressure, causing a pumping action in the disc. The influx and outflux of water transports nutrients in and flushes out metabolic waste products.

Where are contact forces greatest in the spine?

L5-S1 facet joints

For what is lordosis a risk factor?

Low back pain development

What other factors can negatively affect disc nutrition? Help it?

Neg affect: habitual smoking and exposure to vibration Pos affect: regular exercise

What are the four normal spinal curves, what direction are they in (concave anteriorly or posteriorly), and are they primary or secondary?

Primary: -Thoracic and sacral curves: concave anteriorly. Present at birth Secondary: -Lumbar and cervical curves: concave posteriorly. Not present at birth

How does a) limited hip extension, b) obesity, and c) running affect lordosis?

a) Limited ROM in hip extension associated with exaggerated lumbar lordosis b) Obesity causes reduced ROM of entire spine and pelvis. Individuals display greater anterior pelvic tilt and an associated increased lumbar lordosis c) Increased anterior pelvic tilt and increased lordosis are greater during running than walking.

What are the 2 functional structures of IV discs?

annulus fibrosus nucleus pulposus

lig of spine that connect vertebral bodies in the cervical, thoracic, and lumbar regions: which is stronger?

anterior and posterior longitudinal ligs anterior

6 ligaments of the spine:

anterior longitudinal lig posterior longitudinal lig supraspinaous lig interspinous lig intertransverse lig ligamentum flavum

What's the axis?

axis: second cervical vertebrae; articulates with atlas and forms the atlantoaxial joint which permits rotation, extension, and lateral flexion.

5 regions of the spine and number of vertebrae in each:

cervical- 7 thoracic- 12 lumbar- 5 sacral- 5 fused coccygeal- 4 fused

in what two groups is scoliosis primarily seen?

children 10-13 years old. more common in females

small lateral deviations in spinal curvature are relatively common and may result from a habit such as carrying books or a heavy purse on one side of the body every day. -70-90% of cases are labeled ___ - the cause isn't known

common idiopathic

What is the most common form of loading?

compression

What are the possible causes of lordosis? ___ spinal deformity, weakness of ___ muscles, poor ___ habits, and ___ in sports requiring repeated lumbar ___ like gymnastics, figure skating, etc.

congenital ab postural overtraining hyperextension

What are the possible causes of kyphosis? ___ abnormality, pathology such as ___, or ___, in which one or more wedge shaped vertebrae develop bc of abnormal epiphyseal plate behavior.

congenital osteoporosis scheuermann's disease

possible causes for structural scoliosis development: (2)

congenital abnormalities selected cancers

Ligamentum flavum: Contains high proportion of ___ fibers, which lengthen when stretched during spinal ___ and shorten during spinal ___. It's in tension even when spine is in anatomical position, enhancing spinal ___. Tension creates a slight, constant compression in intervertebral discs called ___.

elastic flexion extension stability prestress

What's kyphosis?

exaggerated thoracic curvature

what's the neural arch of a vertebrae?

form a protective passageway for spinal cord and associated blood vessels known as the vertebral canal

What are the results of the changes to the discs as a result of injury and aging? -reduced ___ of spinal column, often accompanied by ___ changes in the spinal structures that are forced to assume the loads of the discs. ___ alterations may also occur when the normal lordotic curve of the lumbar region may be reduced as a person attempts to relieve compression on facet joints by maintaining a posture of spinal ___.

height degenerative postural flexion

These spinal curves are influenced by what? (4)

heredity, pathological conditions, individual's mental state, forces to which the spine is habitually subjected.

type of scoliosis in which low bone mineral density is typically associated with. May play causative role in development

idiopathic

ligaments that connect vertebrae through transverse processes

intertransverse ligaments

scoliosis: ___ deformity coupled with ___ deformity of involved vertebrae. Ranges from mild to sever. May appear as either a(n) ___- or a(n) ___-curve involving ___ spine, ___ spine, or both. Same ___ shaped vertebrae as seen in kyphosis.

lateral rotational C, S thoracic, lumbar wedge

what's scoliosis?

lateral deviation or deviations in spinal curvature.

ligament that connects laminae of adjacent vertebrae.

ligamentum flavum

possible causes for nonstructural scoliosis development: (2)

may occur secondary to a leg length discrepancy or local inflammation

spinal movements always involve a number of ___

motion segments

scoliosis in which the vertebrae are flexible and are corrected with lateral bending

nonstructural

What's the body of a vertebrae?

primary weight bearing components of the spine

what are the bony processes of a vertebrae? what is their function?

protrude from neural arch. Spinous and transverse processes serve as outriggers to improve mechanical advantage of the attached muscles.

What type of strain is the annulus fibrosus most susceptible to?

rotational strain

spinal rotation creates ___ stress within the discs, with the greatest shear around the periphery of the ___.

shear annulus fibrosus

scoliosis that involves inflexible curvature that persists even with lateral bending of spine.

structural

2 types of scoliosis:

structural, nonstructural

ligaments that attaches to the spinous processes through length of spine. Enlarged in cervical region, where it's referred to as the ligamentum nuchae.

supraspinous ligament

When the spine bends, a(n) ___load is created on one side of the discs, and a(n) ___ load is created on the other

tensile compressive

Mechanically, the spinal curves purpose is what?

they enable the spine to absorb more shock without injury than if the spine were straight.

Spinal ligs all behave in a ___ fashion, stretching in response to strain in a nonlinear, time-dependent fashion.

viscoelastic

When a disc is loaded in compression... -It tends to simultaneously lose ___ and absorb ___ and ___ until its internal electrolyte concentration is sufficient to prevent further ___ loss. When this chemical equilibrium is achieved, internal disc pressure is ___ to the external pressure. Continued loading over a period of several hours results in a further slight ___ in disc hydration

water sodium, potassium water equal decrease