Vertebral Column

Vertebrae

  • cervical (C1-4-T2) and lumbar (L1-3-5) lordosis = secondary/ compensatory curves
  • thoracic (T2-7-12) and sacrococcygeal kyphosis = primary curves
  • physiological right lateral thoracic scoliosis
  • anterior compartment/column (ALL, bodies, discs)
  • middle column (PLL, posterior annulus fibrosus, posterior body)
  • posterior compartment/column (neural arch, lig flava)
  • vertebral body
  • vertebral/neural arch
  • pedicles
  • intervertebral/neural foramen
  • pars interarticularis
  • superior and inferior articular processes/facets
  • transverse process
  • laminae (thickness <14mm)
  • spinous process
  • cortical/compact bone
  • cancellous/trabecula bone
  • vertical/weight-bearing trabeculae (0.2-0.5mm)
  • horizontal/connecting trabeculae (<0.2mm)
  • red/haemopoietic > yellow/fatty bone marrow
  • symphyses (IV discs), synovial (facet) and syndesmoses (fibrous ligs) joints

Facet/Zygapophyseal Joints

  • inferior facet posterior to superior facet
  • hyaline cartilage
  • joint capsule (tough posterolateral lumbar, none ventral)
  • cervical 45° to vert with menisci, superior facets face post-sup
  • thoracic 30° to vert superior facets facing post-sup-lat > post-med
  • lumbar near vert L1 45° post-med and L5 face post
  • A = ligamentum flavum
  • < medial division of posterior primary ramus from level above

Atlanto-Occipital Joint

  • synovial, occipital condyles and lateral masses, centre of gravity of head anterior to joint; flexion, extension, lateral flexion
  • atlanto-occipital capsule (thickened posterior and lat)
  • Chamberlain’s line (on lat) posterior tip hard palate > foramen magnum; <2mm odontoid above this
  • McGregor’s line (on lat) posterior tip hard palate > base occiput; <5mm odontoid above this
  • digastric line (on OF) digastric notches of mastoid processes; atlantooccipital joints below this

Atlas (C1)

  • anterior arch
  • anterior tubercle
  • articular facet for dens
  • lateral articular masses
  • foramen transversarium = transverse foramen (vertebral a, sympathetic nn)
  • tubercle at ant-med lateral masses < transverse lig
  • superior articular facet (face ant-med, concave > occipital condyles)
  • inferior articular facet (post-med, flat)
  • posterior arch
  • groove for vertebral a (sup, behind lateral masses)
  • posterior tubercle (<ligamentum nuchae)
  • transverse processes

Atlanto-Axial Joints

  • median atlanto-axial joint (synovial, anterior arch atlas and dens, synovial burasae; rotation)
  • lateral atlanto-axial joint (synovial, between lateral masses)
  • atlantoaxial distance <3mm adult; <5mm child (unossified cartilage)

Axis (C2)

  • odontoid process = dens (body of C1, compact bone)
  • anterior (>ant arch atlas) and posterior (>transverse lig) articular facets
  • superior facets (face post-sup-lat)
  • bifid spinous process
  • foramen transversarium (face superolateral)

Cervical Spine (C3-C7)

  • ovoid-shaped bodies, triangular vertebral canal
  • uncinate process (lateral margin of superior body)
  • uncovertebral/neurocentral joints (of Luschka) (>bevelled notch on posterolateral vertebra above)
  • transverse process anterior and posterior tubercles (ant largest on C6, almost absent C7)
  • foramen transversarium (L>R, occasionally double; vertebral aa&vv, sympathetic nn; small/absent in C7 with only vv)
  • articular masses/pillars = lateral column on AP
  • superior facet (post-sup)
  • bifid spinous processes (C3-C6)
  • vertebra prominens = C7 (long non-bifid spine > lower extremity ligamentum nuchae)
  • flexion/extension causes forward/backward translation of bodies continuously or step-like with <3mm offset
  • prevertebral soft tissue
  • cervical rib (V6%, prolongation costal elements C7

Thoracic Spine (T1-12)

  • wedge-shaped bodies > kyphosis, concave lateral margins
  • pedicles from upper ½ body
  • transverse processes slope post-inf-lat
  • spinous processes long and slender slope down
  • superior articular facets (post-lat T1-10, post-med T11-12)
  • superior and inferior demifacets/costal facets (post bodies T2-10 < rib heads, T1 complete facet superior and demifacet inf, T11-12 complete single facets)
  • costovertebral joints (synovial)
  • intra-articular ligament (crest of rib head > intervertebral disc dividing joint into two compartments)
  • transvese costal facet (T1-10 anterior surface > tubercles of ribs)
  • costotransverse articulations (capsule strengthened by accessory costotransverse lig)
  • paravertebral space and line (LNs, intercostal vessels, sympathetic nn, fat)

Lumbar Spine (L1-L5)

  • kidney-shaped bodies, convex anterior and lat, concave/flat post
  • L3 largest and longest transverse process
  • superior facets face post-med
  • spinous process square and horizontal
  • mammillary process (on posterior superior facet)
  • pars interarticularis
  • facet joint at level of disc
  • L5 body wedge-shaped taller ant; inferior facet faces ant-lat; transverse process short, strong and arises from pedicle/body
  • pedicle thinning and slight increase in interpedicular distance (V7%)

Lumbosacral Joint

  • angle 25-55° supine, increasing 8-12° erect
  • iliolumbar ligament (L4 and L5 transverse process > iliac crest, may calcify)
  • lumbosacral ligs (lower band of iliolumbar lig >lat S1, ventral sacroiliac lig)
  • ant and posterior lumbosacral ligs
  • lumbosacral disc <5-10mm and straight/convex post
  • anterior epidural fat

Ligaments

  • anterior longitudinal lig (ALL, basiocciput > sacrum; deep [>adj vert], intermediate >[2-3] and superficial [>4-5] layers; more firmly attached to discs)
  • posterior longitudinal ligament (PLL; body axis/tectorial membrane > sacrum; A = discs, basivertebral v, epidural venous plexus; >dura)
  • supraspinous ligament (tips spinous processes C7/ligamentum nuchae > sacrum)
  • ligamentum nuchae (external occipital protuberance > C7 spinous process; bilaminar intermuscular septum)
  • interspinous lig (adjacent borders spinous process, well-developed lumbar)
  • ligamentum flavum (sup anterior lamina > inferior posterior lamina, cont with capsules of facet joins; V-shaped containing epidural fat; lumbar 3-5mm; yellow elastin fibres)
  • intertransverse lig (weak)

Craniocervical Ligaments

  • anterior atlanto-occipital membrane (upper anterior arch of atlas > outer margin foramen magnum)
  • posterior atlanto-occipital membrane (post arch, lateral mass > foramen magnum)
    • arcuate foramen (at groove for vertebral a; calcification of membrane; vertebral a, suboccipital n)
  • tectorial membrane = membrana tectoria (continuation of PLL, >ant foramen magnum and dura)
  • cruciate/cruciform ligament
    • transverse ligament of the atlas (6mm)
    • superior and inferior longitudinal bands (>basiocciput and body of axis)
  • apical ligament (dens > anterior foramen magnum)
  • alar ligaments (dens > occipital condyles, limit rot)
  • accessory atlantoaxial ligaments (deep to tectorial membrane)

Intervertebral/Neural Canal/Foramen

  • superior and inferior vertebral notches
  • narrowed in T spine and with extension
  • transforaminal ligment (T/L spine)
  • neural elements (ventral root, dorsal root and ganglion, spinal nn; in upper part of T/L spine with foraminal/epidural fat; lower part of C-spine with little fat)
  • foraminal veins (upper cervical canals)
  • C-spine directed 45° anterolateral, T/L spine lateral
  • sinuvertebral = recurrent meningeal nerve of Luschka (spinal n > re-enters spinal canal > posterior annulus, PLL, periosteum, meninges)

Relations

  • A = vert body and disc (in C-spine body below)
  • P = ligamentum flavum, facet joint and capsule
  • S/A = head of ribs
  • S&I = pedicles

Vertebral/Spinal Canal

  • Extradural, intradural and intramedullary spaces.
  • AP width of spinal canal: atlas 16-27mm, axis 15mm, lower cervical 13-21mm, lumbar 15-25mm
  • interpedicular width of spinal cord expansions at C5/C6 and T12 and increases from L1-L5 (>20mm)
  • perimedullary space (thoracic 3mm, cervical 8mm)
  • lateral recess = radicular canal (ant-lat portion of canal; A = body/disc; P = base superior facet; lateral = pedicle; descending nerve roots; >3mm AP di)
  • anterior epidural space increases C > S, divided by midline fibour septum >body and PLL
  • posterior epidural space larges at L3-L5

Ossification of the Vertebrae

Vertebra

  • 1° oss in centrum and neural arches (2; posterior fuse L[1y] > C[7y] > S, anterior fuse with body C[3y] > L[6y] > S)
  • neurocentral joint/synchondrosis (betw centrum and neural arches
  • atlas posterior synchondroses fuse (2) 4y; anterior synchondrosis fuses 7y
  • axis (as for atlas and 2 centres for dens fuse 3y)
  • 2° ossification centres:
    • epiphyses of vertebral bodies (appear 16y, fuse 25y)
    • tips of spinous processes (two where bifid), transverse process and mamillary process of T12 and L-spine (appear 16y, fuse 25y, or accessory ossicles)
    • costal elements (connect transverse process to body; from ribs in T-spine; in sacrum fuse with neural arch at 5y and body in early 20s)
    • tip of dens appears at 3y, fuse at 12y

Variants

  • transitional vertebra (20%; features intermediate between types of vertebrae)
    • atlas assimilated into occipital bone
    • occipital vertebrae
    • C7 low transverse process ± cervical rib
    • L1 rib
    • presacral vertebra (6th lumbar vertebra)
    • sacralisation (L5 with one/both transverse process and inferior body partly fused)
    • lumbarisation of S1
  • asomia (agenesis of vertebral body)
  • hemivertebra = wedge vertebra (incomplete development on one side)
  • butterfly vertebra (failed fusion lateral halves with persistence of notochord tissue)
  • block vertebra = congenital synostosis (absence of segmentation, complete or pseudoarthrosis between transverse processes and sacral ala)
  • coronal cleft (failed fusion of anterior and posterior ossification centres)
  • failed fusion of L/S arches <4mm (<20%)
  • post spina bifida = failed fusion posterior arch atlas (2-6%)
  • ant spina bifida = failed fusion of variant 2 anterior arch ossification centres (usually fuse 8y)
  • os odontoideum (failed fusion tip of dens with cartilaginous disc)
  • spina bifida occulta (5-10%; defect in ossification neural arch, covered with skin). Form of spinal dysraphism

Intervertebral Disk

  • amphiarthrodial = symphysis joints (with intervening disc)
  • hyaline cartilage
  • fibrocartilaginous disc (avascular after puberty, nutrition diffuses through endplates)
  • annulus fibrosus = fibrous lamellae(80% water, relatively thin posteriorly)
    • external/collagenous annulus/endplate (type I collagen; thick Sharpey’s fibres > apophyseal ring [edges of vertebrae]), central depression with hyaline cartilage
    • internal/fibrocartilaginous annulus (type II collagen and proteogylcans; fine fibres > endplate hyaline cartilage)
  • central zone/complex (internal annulus and nucleus pulposus)
  • nucleus pulposus (notochord remnant; gelatinous proteoglycans and type II collagen; 85-90% water; replaced by fibrous tissue >80y; uni- or bi-locular)
    • intranuclear cleft (>30y, absent in 6%; compacted transverse fibres, invagination of inner annulus)
  • dehydration and loss of disc height with age
  • thinnest upper thoracic, thickest lumbar; wedge-shaped in C and L giving lordosis
  • 20% of vertebral column height

Paraspinal Muscles

Anterior/flexor group (<ant rami)

  • rectus capitis (lat mass and transverse process atlas > basion; posterior to longus capitis)
  • longus capitis (basion > anterior tubercles transverse processes C3-6)
  • longus colli (ant tubercles C3-5 > anterior arch atlas; anterior tubercles C5-6 > bodies T1-3; bodies C2-4 > bodies C5>T3)
  • sternocleidomastoid (flex C-spine)
  • posas major (T12-L5 bodies, discs and transverse processes > lesser trochanter femur; accessory ossicle [V])
  • psoas minor (ant to psoas major)
  • rectus abdominis (flex L-spine)
  • flank/oblique muscles (rotate L-spine)

Posterior/extensor group (<post rami; in vertebral grooves)

  • superficial layer = erector spinae (iliocostalis [lat], longissimus, spinalis [med])
  • intermediate layer
  • deep layer

Movements of the Vertebral Column

  • about axis of nucleus pulposis
  • flexion (limited by tension in posterior vertebral mm), extension, abduction/lateral flexion in C/T/L
  • rotation in upper T-spine

Blood Supply

  • atlas/axis < ascending pharyngeal, ocipital aa
  • cervical segmental branches < vertebral a, costocervical and thyrocervical trunks
  • T/L < intercostal aa, lumbar segmental aa (<aorta)
  • sacral < lateral sacral a < internal iliac a
  • basivertebral vv (Y-shaped channel in body) > internal vertebral/epidural venous plexus (anterior and posterior longitudinal vv) > intervertebral v >segmental vv > paraspinal vv
  • external vertebral venous plexus (<mm) > segmental vv
  • veins are valveless hence reflux increases spread of disease to spine