Chapter 7 Functional Anatomy of the Trunk - PowerPoint Presentation

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Chapter 7

Functional Anatomy of the Trunk

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The

Vertebral Column

The vertebral column acts as a modified elastic rod, provides rigid support and flexibility.

The column consists of 33 vertebrae, 24 of which are moveable.

The column also protects the spinal cord.

The vertebrae are arranged into four curves that facilitate support.

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Anatomical and Functional Characteristics of the Vertebral Column

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Motion Segments of the Spine

Functional unit of the vertebral column

Similar in structure throughout spinal column, except first two cervical vertebrae

Consists of two adjacent vertebrae and the disc that separates them

Anterior portion

Vertebral bodies, intervertebral disc, and ligaments

Posterior portion

Vertebral foramen, neural arches, intervertebral joints, transverse and spinous processes. and ligaments

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Motion Segment

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Anterior Motion Segment

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Anterior Motion Segment (cont.)

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Posterior Motion Segment

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Structural and Movement of Each Spinal Region

Cervical region

Very mobile

Two atypical vertebrae (atlas and axis)

Atlanto-occipital joint—head nodding

Atlantoaxial joint—most mobile of the cervical region, allows to turn head

Thoracic region

Very restricted movement

Connection to ribs, orientation of facets, and long spinous processes restrict the movement

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Regions of the Spine

Lumbar region

Most highly loaded structure in the skeletal system

Large vertebrae to distribute load

Thick intervertebral discs

Large range of motion in flexion and extension

Sacrum and coccyx

Fused vertebrae

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Range of Motion in Individual Motion Segments

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Movements of the Total Spine

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Combined Movements of the Pelvis and Trunk

Lumbopelvic rhythm—movement synchronization between the pelvis and the trunk

Lumbar activity is maximum through first 50°–60° of flexion followed by anterior pelvic rotation to increase trunk flexion

Reverse for trunk extension, pelvic posterior tilt initiates followed by lumbar activity

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Muscular Actions

Trunk extension

Erector spinae (iliocostalis, longissimus, spinalis)

Deep posterior muscles (intertransversarii, interspinales, rotatores, multifidus)

Trunk flexion

Abdominals (assisted by psoas major and minor)

Trunk lateral flexion

Contraction of muscles on both sides of vertebral column with most activity on side to which lateral flexion occurs

Trunk rotation

Complicated recruitment pattern of muscles on both sides of the vertebral column

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Strength and Forces at the Vertebral Joints

Trunk extension strengths average 210 Nm.

Trunk flexion strengths average 150 Nm.

Trunk lateral flexion averages 145 Nm.

Trunk rotation strengths average 90 Nm.

Intra-abdominal pressure, ligaments, and other structures also contribute to the net strength moments.

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Posture

Standing

S-shaped spine acts as an elastic rod support.

Erector spinae helps keep spine erect.

When slouching, the ligaments and joint capsules maintain posture.

Sitting

Unsupported sitting places more load on lumbar spine.

When sitting, flattens the back, and shifts the center of gravity forward.

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Postural Deviations

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Conditioning

Conditioning should focus on flexibility and resistance training for the entire trunk musculature.

The musculature should be stretched and resistance trained in extension, flexion, lateral flexion, and rotation with special emphasis on the lumbar and cervical regions.

Endurance training for back muscles better for preventing back injury.

Trunk exercises should take place with the spine in a neutral position using co-contraction of the abdominals.

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Injury Potential

85% of the general population of the Western world report back pain at some time in their lives.

For 1% to 5% of the population, low back pain is a chronic problem.

It usually recurs 30% to 70% of the time after initial incidence.

However, back pain is uncommon in children and athletes.

Only 2% to 3% of the total sprains in the athletic population are to the back.

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Disc Degeneration

Low back pain is most common from 25 to 60 years of age.

Highest incidence at age 40.

Most of these problems are due to muscle or tendon strain, only 1%–5% relate to disc injury.

However, disc generation progresses as we age, causing splits and tears in the disc tissue.

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Disc Degeneration (cont.)

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Lifting

Injuries to the low back from lifting are primarily a consequence of the weight of the load and its distance from the body.

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Effects of Aging on the Trunk

Flexibility may decrease to as little as 10% of that of younger individuals

Trunk muscles lose approximately 1% of their strength per year

Between ages 30 and 80, strength losses are:

Approximately 30% in cartilage

Approximately 20% in bone

Approximately 18% in ligaments

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Effects of Aging on the Trunk (cont.)

The shape and length of the spine change with age

Smaller fluid region in aging discs places more stress on annulus fibrosus

Height of discs may reduce

Increased lateral bending

Lumbar lordosis decreases

Unclear if changes are part of the normal aging process or associated with abuse and disuse of the trunk

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Contribution of Trunk Musculature to Sports Skills or Movements

Obvious involvement in lifting, back extension, and sit-ups (flexion).

Trunk is important in stabilizing torso during most movements.

Trunk muscles also contribute to activities such as walking and running.

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Forces Acting at Joints in the Trunk

Loads applied to the vertebral column are from:

Body weight

Muscular force on each motion segment

Prestress forces from discs and ligaments

External loads

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Tennis Serve

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Clinical Applications

Chronic low back pain

Second leading cause of disability worldwide

Most common musculoskeletal condition affecting adults

Two main pain mechanisms

Nociceptive—from activation of specialized sensory pain receptors that respond to damaging stimuli

Neuropathic—pain arises from a disease or injury directly influencing the nerve roots or from pain from damaged lumbar discs

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Clinical Applications (cont.)

Many types of back pain can be categorized as:

Mechanical (axial) pain, radicular pain, referred pain, facet joint pain, sacroiliac joint pain, lumbar spinal stenosis, discogenic pain

Treatment

Goals are to reduce pain, maintain function, and prevent exacerbation of the condition

Range from pharmacological therapy, injections, acupuncture, massage, spinal manipulation, and physical therapy

Little evidence to assess treatment options

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Summary

Flexibility and stability

Cervical, thoracic, lumbar, and sacral curves

Motion segment of spine

Motion (flexion, extension, rotation, lateral flexion)

Pelvis motion crucial (lumbopelvic rhythm)

Stabilization systems (passive, active, neural feedback)

High incidence of back pain

Stretching and strengthening exercises are crucial to maintain a healthy trunk