Chapter 18 Flashcards by Kestrel Martin

Define spine posture

The orientation of the vertebrae in the spine (in a given condition).

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Describe the expected global spine curvatures in a healthy adult. Why are these curvatures important?

The adult has 3 global spine curvatures - cervical, thoracic and lumbar.

Cervical: lordosis curvature with a Cobb angle of 30-35 degrees

Thoracic: Kyphotic spine curvature with a Cobb angle of 40 degrees Thoracic

Lumbar: lordosis curvature with a cob angle of 45 degrees Thoracic

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Describe how to measure global spine curvatures using the Cobb angle.

The adult has 3 global spine curvatures - cervical, thoracic and lumbar.

Cervical: lordosis curvature with a Cobb angle of 30-35 degrees

Thoracic: Kyphotic spine curvature with a Cobb angle of 40 degrees Thoracic

Lumbar: lordosis curvature with a cob angle of 45 degrees

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What is the term for curvature of the spine in the frontal plane?

Scoliosis - this is abnormal.

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Define a functional spinal unit.

A functional spinal unit is comprised of two vertebrae that articulate with one another. This includes ligaments and disks. Muscles are ignored.

This articulation can be used to define the local spine angle as well as describe spine posture.

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What are the three articulations within an FSU?

Articulation between the vertebral bodies (IV disk)
Articulation between the left and right facet joints (posterior aspect of the neural arch, running between SP and TP’s)

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Spinal flexion occurs on which axis?

The medial-lateral axis.

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What are the anatomical and mathematical definitions of a joint?
How is the spine considered a joint from a mathematical perspective?

Anatomical: articulation formed between the surfaces of two adjacent bones (eg FSU)

Mathematical: relative orientation between two rigid bodies (regardless of whether or not objects are in contact).

The measurement of the Cobb angle is an example of how the spine is considered a joint from a mathematical perspective. The Cobb angle measures the relative orientation of two vertebrae that are not adjacent to each other.

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Differentiate between global and local angels of the spine.

Global:
- Cobb angle
- angle between most superior and most inferior vertebrae in one region of the spine
- cumulative orientation of all FSU in the spine region

Local:
- angel between a pair of adjacent vertebrae
- changes in the angle at one FSU may not be reflected in the global angle

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What feature is most important for spinal posture? Why? How is this measured?

The Sacral Slope or orientation of the sacrum.
Measured as the slope of the sacrum relative to horizontal. In standing, this angle should be roughly 40 degrees.

Changes in the sacral slope angle have the potential to effect vertebrae all the way up the kinetic chain - lumbar, thoracic, cervical.

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How effective are visual posture assessments when compared to motion analysis using inertial measurement units?

Not accurate at all - even when done by physiotherapists.

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How accurate is motional analysis of spinal postures when compared to videofluoroscopy (x-ray video)?

Far from accurate.

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What is the maximum flexion and extension that can be performed by the lumbar spine?

Extension:
Global: 16 degrees
Local: 1-5 degrees/FSU

Flexion:
Global: 50 degrees
Local: 1-13 degrees/FSU Flexion

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How do spinal injuries occur?

Excessive rotation (in any plane) that exceeds the limits of a particular joint. This is usually a result of decreased spine stability.

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Define stability.

How well a physical object can maintain its configuration and withstand forces. The more resistant a system is to change, the more stable it is.

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Define the neutral zone.

The neutral zone is the region of intervertebral motion associated with a neutral posture, where passive structures of the spine (ligaments) offer minimal resistance to movement/forces (they are slack). In this zone, small forces produce relatively large spinal rotations. Thus stabilizer muscles are large contributors to stability in this range.

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Differentiate between local and global muscles of the spine.

Local:
- deep muscles
- small physiological CSA
- cross few FSU
- PRIMARY STABILIZERS

Global:
- superficial
- large physiological CSA (designed to generate large amounts of force)
- Cross many FSU
- secondary stabilizers

Which muscles are considered primary and secondary stabilizers of the spine?

Global (secondary):
- erector spinae (three sets)
- rectus abdominus and obliques

Local (primary):
- transversospinal muscles: multifidus, rotatores longus and brevis and semispinalis
* attach from TP’s to SP’s*

Which deep stabilizer muscles contribute to flexion?

Psoas major
Scalenes
Longus colli

How do deep muscles stabilize the spine?

Generating moments of force to resist the moments attempting to move the FSU through the neutral zone.

What moments are generated by the multifidus muscle?

spinal compression
lateral flexion
extension
axial rotation
stabilizes the spine around various axis*

The atrophy of which muscles is found in people with low back pain?

multifidus
psoas major

both stabilizers of the lumbar spine

When is the psoas major the strongest?

When the spine is in flexion is when this muscle acts to stabalize the spine best.

When is the multifidus muscle the strongest?

In anatomical position, the multifidus has a sarcomere length that is on the ascending limb II of the force-length relation. When the spine flexes, the sarcomeres lengthen, (moving towards the plateau region) making the multifidus strongest during spinal flexion.

What are the benefits of performing strenuous daily activity on spine health?

- decreased fat infiltration of spine stabilizers - increased IV disk height

What three components comprise the vertebral disk?

Vertebral endplate Annulus fibrosis Nucleus pulposus

What postures increase disk pressure from standing upright? Why do these postures increase compressive forces?

- bending forward - sitting upright - sitting bent forward It is the activation of stabilizer muscles in these postures that increase compression forces of the spine.

When carrying a moderate load, by how much does the combination of the load and body weight contribute to spine compression forces? What about stabilizer muscles?

25% - load + BW 75% - muscles

During a “stoop” lifting technique (as opposed to a “squat” lift), the moment arm is increased and thus the compression forces. Why is this counterintuitive?

Because people with healthy backs often lift with a stoop posture (when they are expected to lift with a squat posture), while people with low back pain lift with a squat posture as a compensatory strategy. However, as they fatigue, they also move to the stoop posture becasue it is more efficient.

What conditions must be accounted for when assessing how much force the spine can tolerate?

1 - the compression forces 2 - amount of times the compression force is applied

What is the upper safety limit of spinal compression forces according to the national institute for occupational safety?

3500N for activities performed 100 - 1000 times per day. - lifting roughly 20 kg’s 6400N for activities performed less than 100 times per day These limits are designed for an 8 hour work day and to accommodate 75% of females and 100% of males

Why aren’t compressive forces responsible for back pain? What study proved this?

Because the spine can tolerate high amounts of compressive forces as reveled by studying cadavers. For example, an 80kg individual can tolerate a 122kg load before spinal failure. Therefore, large compressive loads are not the major cause of back problems. *these findings depend on the size of the individual and how active they are*

What is a duty cycle? Describe a normal duty cycle.

A duty cycle is a cycle of on and off. This concept can be applied to work and rest ratios or even to gait with stance and swing phases qualifying as a duty cycle. A normal duty cycle for the spine involves periods of loading and unloading. During the loading phase compressive forces are applied, which strains the ligamentous spine. During the unloading phase, the compressive forces are removed and there is a cellular response to recover from the imposed strain.

Describe abnormal duty cycles - referring to spine compression.

1 - Inactivity: no cellular response are initiated, and tissue degeneration begins 2 - chronic exposure: the cellular response is inhibited because the spine is loaded, leading to tissue degeneration.

How long after engaging in bed-rest, does muscle atrophy of the spine stabilizers begin?

3-4 days *longer periods of bedrest will result in decreased disc height and this cannot be restored within 6 months (according to the space study)*

What were the findings of the chronic compression study which measured morbidly obese individuals before and after surgery?

After 1 year post-injury, their disk height increased by 2 cm!!! Their back and radicular pain also decreased significantly. Being obese is an example of an abnormal duty cycle, involving excessive loading.

What is radicular pain?

When chronic compression forces are applied, the disk height, as well as the size of the neural foramen decreases. Accompanied by excessive back extensor muscle activation, this can cause further compressive forces in the spine. This can cause a disk herniation which may compress the nerve root exiting the neural foramen.

What causes chronic exposure to spine compression?

- high BMI - chronic muscle tension (abnormal posture, excessive activity, stiff muscles)

How does a forward head posture lead to increased spinal compression?

This posture places the weight of the head in front of the spine. To hold this position requires substantial erector spinae activity, which creates large compression forces in the mid to low back.

What percentage of adults are expected to experience low back pain in their life?

80%

What are the recommendations to maintain a healthy back?

1 - lifestyle factors - decrease sedentary behaviour - focus on good posture and avoid sitting for long periods - dont accumulate excessive body fat 2 - Daily strenuous Activity - do daily exercises involving all spine ROM - 20 minutes a day is sufficient - for healthy individuals no restrictions are placed on ROM 3 - Targeted PA - This is not required but can be used to develop or restore spine health - progressive overload of spine compression - can do an appropriate amount of lumbar spine flexion and extension to strengthen stabilizer muscles *Take-away: dont restrict movement types! The spine can be flexed during activities as long as it isn’t near an end ROM*