Clinical spinal anatomy

Mr. Daniel Chan FRCSEd FRCSOrth

Consultant Orthopaedic Spinal Surgeon

PEOC/RD and E

Anatomy of the SpineAnatomy of the Spine

Cervical spine7 vertebraeC1 - C7

Thoracic spine12 vertebraeT1-T12 (D1-D12)

Lumbar Spine5 vertebraeL1-L5

Sacrum & Coccyx5 fused vertebraeS1-S53-5 Coccygeal segments

ANTERIOR COLUMN• solid column of

vertebral bodies• compression-

resistant

POSTERIOR COLUMN

• hollow column of neural canal

• tension-resistant

• Axial skeleton• Protection of neural

structures• Flexible weight bearing

column• Anterior compression

column• Posterior tension

column• Facets resist rotation

and anterior displacement

Sagittal profile

• To maintain upright balance

• Cervical and lumbar lordosis

• Thoracic and sacral kyphosis

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11223344

55

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upper cervical spine - Axial

lower cervical spine – Sub-Axial

Anatomy - Osteology

• Occiput– Inion – external occipital protuberance– Transverse sinus close proximity– Occipital screws just below inion (thick)

• Typical - C3-6

• Atypical - Atlas, Axis, C7 (vertebra prominens)

Restricts rotation of occiput on dens

Major stabiliser C1-C2

Major ligs of subaxial spine+ lig flavum + inter + supra spinous ligs

C0-C2 Joint surfaces very unstableStability via ligaments

Steel’s Rule of Thirds1/3 Dens1/3 Cord1/3 Space

Feel your own!

For feeling the pulse!

Tripod = VB +2 Facets / Lateral masses

Scalenes ant + med

Uncinate ProcessUncovertebral Joints of LuschkaLimit Lateral Translation or BendingGuide Rail for Flexion / Extension

Anatomy - Articulations

• Arc of motion:

• Flexion/Extension 145°

• Axial rotation 180°

• Lateral flexion 90°

Anatomy - Articulations

• 50% cervical flex / ext @ Co-C1

• 50% cervical rot @ C1-C2

• Rest motion in sub-axial spine by “coupling” action of motion segments

• Sub-axial cervical facet joint orientation unique– 45˚ sagittal– 0˚ coronal

• Permits flex / ext / lat bend / rot

Anatomy - Neural

• 8 Cervical nerves

• 7 Vertebrae

• Dorsal root + DRG = sensory

• Ventral root = motor

• Unite = spinal nerve

• Dorsal ramus = to the back

• Ventral ramus = to the front

• Sinuvertebral nerve = to the spinal column

Anatomy - Neural

Starting point 1mm medial to centre of lateral mass

Starting point 1mm medial to centre of lateral mass

1mm15o

Vertebral artery anterior to entry point

Vertebral artery anterior to entry point

Pedicles small and highly variableTherefore – lateral mass screws

Place a flat probe in the facet joint of the level to be fused to indicate the cephalad angulation of the drill or ‘K’ wire

Place a flat probe in the facet joint of the level to be fused to indicate the cephalad angulation of the drill or ‘K’ wire

greateroccipitalnerve

vertebralartery

sub-occipitalnerve

posterioratlantooccipitalmembrane

axis

atlas

atlanto-axialjoint

spinal cord

vertebralartery

Atlanto-axial dislocations-surgical stabilisation

Atlanto-axial dislocations-surgical stabilisation

• Magerl transarticular screw fixation• Magerl transarticular screw fixation

Atlanto-axial dislocations-surgical stabilisation

Atlanto-axial dislocations-surgical stabilisation

• Gallie C1/2 wiring• Gallie C1/2 wiring

Atlanto-axial dislocationSurgical stabilisation

Atlanto-axial dislocationSurgical stabilisation

• Brook Jenkins C1/2 fusion

• Brook Jenkins C1/2 fusion

(Goel) Harm’s C1/2 fixation

DF injury

• example

DF injury

• Reduction of unifacet dislocation

DF injury - redisplacement

• Roger’s wiring

• Bohlman’s triple wiring

Posterior stabilisation

Lateral mass fixation

•12 Vertebrae, Smaller than Lumbar12 Vertebrae, Smaller than Lumbar

•Facets Frontally Orientated in A-P ViewFacets Frontally Orientated in A-P View

•Spinous Processes Longer, Distally OrientatedSpinous Processes Longer, Distally Orientated

•Transition at Thoracolumbar Junction T9-12Transition at Thoracolumbar Junction T9-12

Thoracic Anatomy

Anatomy – general considerations

•transverse processes short transverse processes short but thick, but thick, orientated postero-laterally, orientated postero-laterally, articulate with ribs articulate with ribs

•Pedicles smallerPedicles smaller

•Spinal Canal smaller Spinal Canal smaller diameterdiameter

•Ribs articulate with Ribs articulate with vertebral bodiesvertebral bodies

Anatomy – body and pediclesAnatomy – body and pedicles•Left side flattened Left side flattened due to aortadue to aorta

•Heart shapedHeart shaped

•Pedicles smallest Pedicles smallest at T3-6 (3-4mm)at T3-6 (3-4mm)

•Centre projects Centre projects intersection 1-2mm intersection 1-2mm medial to lateral medial to lateral lamina with parallel lamina with parallel line superior 1/3 tp.line superior 1/3 tp.

Anatomy -costovertebral joints and ribsAnatomy -costovertebral joints and ribs

•11stst, 11, 11thth and 12 and 12thth ribs ribs soleley with named soleley with named vertebravertebra

•2-10 with rostral 2-10 with rostral neighbourneighbour

•Articulate with anterior Articulate with anterior tptp

Structures anterior to thoracic spine

Tomita Procedure

• 55/M(AM)• Back pain+

paraparesis• T7 Mets• Tokuhashi Score-12• Hypernephroma

primary

Tomita procedure (Spine 1997; 22: 324-333)

3 months

28 monthsNo recurrence

Lumbar SpineLumbar Spine• L1 to L4 ‘Typical’ Lumbar

Vertebrae

- wide strong kidney shaped bodies with parallel endplates;

- a wide posterior arch fusing to form a horizontally projecting spinous process

- Superior facets face posteromedially, Inferior facets face anterolaterally and therefore allow flexion/extension but limit rotation

Ligamentumflavum

Interspinous ligament

Anteriorlongitudinal ligament

Posterior longitudinalligament

Intervertebraldisc

Supraspinousligament

Pars interarticularisPars interarticularisSpondylolysis: The Scotty Dog Spondylolysis: The Scotty Dog Spondylolytic spondylolisthesisSpondylolytic spondylolisthesis

• NUCLEUS PULPOSUS– GAGS. Hydrated

Aggrecans– Hydrostatic

structure

• ANNULUS FIBROSUS– fibrocartilagenous

structure with different “mesh-type” layers

L4

L5

Cauda equina and Nerves rootsCauda equina and Nerves roots

Degenerative

• Disc herniations

Anatomy• Thoracolumbar fascia

• Cluneal nerves

• Sacrospinalis– Iliocostalis– Longissimus– Spinalis

• multifidus• rotators• intertransversarii

Anatomy

• crest on pars

• crest on TP

• converge on superior facet

Sacral anatomy

• lateral sacral crest

• junction with superior facet

Sacral anatomy• converge to

promontary

• diverge to ala

Plan screw trajectory

MRI Plain X rays

Anterior relations

Cross section anatomy - L4 L5

• root medial and inferior to pedicle

• great vessels anterior

L4 L5

Cross section anatomy - S1

• “bare” area

• L5 root

S1

L4/5 exposure L5S1 exposure

May the force be with you

Clinical Instability

The loss of the ability of the spine under physiological loads to maintain its pattern of displacement so that there is no initial or additional neurological deficit, no major deformity, and no incapacitating pain

Clinical Instability

The loss of the ability of the spine under physiological loads to maintain its pattern of displacement so that there is no initial or additional neurological deficit, no major deformity, and no incapacitating pain

White and Panjabi Clin Orthopaedics 1975