1 The Trunk/Spine largest segment of body most significant functional unit for general movement...

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The Trunk/Spine

• largest segment of body• most significant functional

unit for general movement• integral role in upper and

lower extremity function• relatively little movement

between 2 vertebrae

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The Vertebral Column

7 cervical vertebraedevelop as an infant begins to lift its head

12 thoracic vertebraepresent at birth

Sacrum - 5 fused vertebraeCoccyx - 4-5 fused vertebrae

Cervicothoracic junction

Thoracolumbar junction

Lumbosacral junction

5 lumbar vertebraedevelop in response to weight bearing

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Vertebral Articulation

Inferior articular process

Superior articular process

• each articulation is a fully encapsulated synovial joint

• these are often called apophyseal joints

Note: the processes are bony outcroppings.

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Costal (Rib) Articulation

Note: the facets are the articular surfaces.

Inferiorcostalfacet

Transversecostalfacet

Superiorcostalfacet

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Spinous process

Transverse processBody

Vertebral foraman

Intervertebral foraman

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Muscular Attachments

• muscular attachments on spinous and transverse processes

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Vertebral shape changes to reflect movements possible within a given region

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Further depictionof vertebral shapes

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Motion Segment: Functional unit of the vertebral column

Two bodies of vertebraecommon vertebral discant & post longitudinal ligaments

Neural archesintervertebral jointstransverse & spinous processesligaments

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Intervertebral Disks‘shock absorbers’ of the spine

capable of withstanding compressive torsional and bending loads

role is to bear and distribute loads in vertebral column and restrain excessive motion in vertebral segment

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Shock Absorbers

Bending Loads

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•2 regions of vertebral diskNPNP -- nucleus pulposus

•gel-like mass in center of disk under pressure such that it preloads disk•80-90% water, 15-20% collagen

AFAF -- annulus fibrosus•fibrocartilaginous material •50-60% collagen

Disc is avascular & aneuralso healing of a damaged disc isunpredictable & not promising

Disc rarely fails under compressionvertebral body will usually fracture before damage to disc occurs

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Ant. Longitudinal ligamentAnt. Longitudinal ligamentvery dense & powerfulattaches to ant disc & vert bodylimits hyperextension and fwd mvmt of vertebrae relative to each other

Post. Longitudinal LigamentPost. Longitudinal Ligamenttravels inside the spinal canalconnects to rim of vertebral bodies & center of discposterolateral aspect of segment not covered - this is a common site for disc protrusionoffers resistance to flexion

Anterior Motion Segment

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Posterior Motion Segment

Bone tissue in the pedicles and laminae is very hard providing good protectionfor spinal cord

Muscle attachments at spinous & transverse processes

articulation between vertebrae occursat superior and inferior facets

these facets are oriented at different angles related to spinal section accounting for functional differences

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Posterior Motion Segment

Ligamentum flavumLigamentum flavum spans laminaeconnecting adjacent vertebral arches very elastic thus aids in extension following flexion of the trunk under constant tension to maintain tension on disc

SupraspinousSupraspinous and interspinousinterspinousligaments span spinous processes resist shear and forward bending of spine

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Spinal Movement

• collectively -- LARGE ROM• flex/ext• L-R rotation• L-R lateral flexion

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MOVEMENTS OF THE SPINEACCOMPANIED BY PELVIC TILTING

1st 50-60º in lumbar vertebrae

Flexion beyond 50º due to anterior

pelvic tilting

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Regional ROM in Spine

Atlas (C1) & axis (C2) account for 50% of rotation in the cervical region.

Thoracic region is restricted, mainly dueto connection to ribs.

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Spine - Posterior Muscular Support

primarily produce extension and medial/lateral flexion• Superficial to deep

– erector spinae– semispinalis– deep posterior

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Spine - Posterior Muscular Supportprimarily produce extension and medial/lateral flexion

• Posteriorly

– erector spinaeiliocostalis

longissumus thoracis

spinalis

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spinalisspinalislongissimuslongissimus

iliocostalisiliocostalis

Erector spinaeErector spinaeVersatile muscles that can

generate rapid force yet are fatigue resistant

thoracis lumborumcervicis

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SemispinalisSemispinalis

thoraciscerviciscapitis

23multifidusmultifidus rotatoresrotatores

Deep posteriorDeep posterior

interspinalesinterspinalesintertransversariusintertransversarius

IT

IS

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rectus abdominis

external obliqueinternal oblique

transverse abdominus

AbdominalsAbdominals

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Intra-Abdominal PressureIntra-Abdominal Pressure acts like a “balloon” to expand the spine thus reducing compressive load, this in turn reduces the activity in the erector spinae

Internal & external obliquemuscles & transverse abdominisattached to the thoracolumbarfascia covering the posteriorregion of the trunk

when these abdominals contract - addedsupport for the low back is created

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Additional muscles contributing to trunk flexion

Collectively known as the iliopsoasiliopsoas

Powerful flexorwhose action ismediated by theabdominals

Quadratus lumborumQuadratus lumborum

forms lateral wall of abdomenalso maintains pelvic position during swing phase of gait

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Movement into fully flexed position

1) initiated by abdominals (1/3 of flexor moment) and iliopsoas2) once it has begun gravity becomes a contributing factor such that the erector spinae act eccentrically to control the movement (thru ~50-60º)3) beyond 50-60º flexion continues by anterior tilt of pelvis this mvmt is controlled by an eccentric action of hamstrings and gluteus maximus while erector spinae contribution diminishes to zero4) in this fully flexed position the posterior spinal ligaments and the passive resistance in the erector spinae resist further flexion5) this places the ligaments at or near the failure strength placing a greater importance on the load sustained by the thoracolumbar fascia loads supported thru the lumbar articulations6) return to standing posture initiated by posterior hip muscles7) erector spinae (1/2 of extensor moment) muscle active initially but peak activity during the final 45-50º of movement

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Strength of Trunk Movements

Extension

Flexion (70% of extension)

Lateral Flexion (69% of extension)

Rotation (43% of extension)

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Postural Alignment

• 2 naturally occurring curves– LORDOTIC (in lumbar

region)– KYPHOTIC (in upper

thoracic lower cervical regions)

– Abnormalities -- accentuated vertebral curves

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Lumbar Lordosis

• exaggeration of the lumbar curve

• associated w/weakened abdominals (relative to extensors)

• characterized by low back pain

• prevalent in gymnasts, figure skaters, swimmers (flyers)

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ThoracicKyphosis

• exaggerated thoracic curve• occurs more frequently than

lordosis• mechanism -- vertebra

becomes wedge shaped• causes a person to “hunch

over”

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Kyphosis

• aka “Swimmer’s Back”• develops in children

swimmers who train with an excessive amount of butterfly

• also seen in elderly women suffering from osteoporosis

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Scoliosis

• lateral deviation of the spinal column

• can be a ‘C’ or ‘S’ shape• involves the thoracic and/or

lumbar regions• associated w/disease, leg

length abnormalities, muscular imbalances

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Scoliosis

• more prevalent in females• cases range from mild to

severe– small deviations may

result from repeated unilateral loading (e.g. carrying books on one shoulder)

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Consequences of Pelvic Tilt

• in normal standing the line of gravity passes ventral (anterior) to the center of the 4th lumbar vertebral body TWTm

• This creates a forward bending torque which must be counter-balanced by ligaments and muscles in the back

• any movement or displacement of this line of gravity affects the magnitude of the bending moment (or torque)

• slouched posture support comes from ligaments – this is bad for extended periods of time

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Pelvic Tilt and Lumbar Loading

• relaxed standing: the angle of inclination of the sacrum (sacral angle) is 30 to the transverse plane

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Pelvic Tilt and Lumbar Loading

• posterior pelvic tilt reduces the sacral angle or flattens the lumbar spine (reduces lordosis)

• causes the thoracic spine to extend which adjusts line of gravity such that muscle expenditure is minimized

• BUT load is now passed on to ligaments

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Pelvic Tilt and Lumbar Loading

• anterior pelvic tilt increases sacral angle

• accentuate lumbar lordosis and thoracic kyphosis

• this adjusts line of gravity to increase muscle energy expenditure

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Pelvic Tilt and Sitting

• Sitting (relative to standing)– pelvis posteriorly tilted– lumbar curvature is

flattened– line of gravity (already

ventral to lumbar spine) shifts further ventrally

– increases the moment created by body weight about the lumbar spine

– increased muscular support increases the load on the spine

vs.

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• erect sitting– pelvis tilts anteriorly– increases lumbar

curvature– reduces the moment arm

of body weight– reduces need for muscular

support– reduces load on lumbar

spine– however, pelvis still much

more tilted than during normal erect standing

vs.

Pelvic Tilt and Sitting

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L3 Load• lowest when

lying supine

• normal when standing upright

• 140% when sitting with no back support

• 150% when hunched over

•180% when sitting hunched over with no back support

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• apparent that lumbar load is strongly related to support needed to maintain lumbar lordosis

• in erect, supported sitting the addition of a back rest reduces lumbar load

• reclining seated position reduces disc pressure even further

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Spinal Injuries

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Progression of Disc

Degeneration

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Degenerative Disks• disk integrity

decreases with

age

• lose ability to retain

water in disk so

disks “dry out”

• ability to distribute

load across disk

changes

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Herniated Disks

• NP protrudes out from between the vertebrae

• nerves are impinged by the bulging NP

• lead to numbness and/or pain

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Disk Herniation

Tearing of Annulus

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Whiplash

Rapid flexion/extension injuries in cervical region

strain posterior ligamentsdislocate posterior apophyseal joints

7th cervical vertebra is likely site for fracture in this injury

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Low Back Pain

1) Muscle strain from lifting may create muscle spasms2) distorted posture for long periods of time3) avoid crossing legs at the knee4) tight hamstrings or inflexible iliotibial band5) weak abdominals

Vertebral

instability

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Lift With Your Legs

• What does this mean?– the idea is to keep the weight (W) as close

to the axis of rotation as possible

Waxis

musculartorque

W

smallermusculartorque

axis