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NOITCES
A B
1
1 9
2
6
2 10
7
11
8
3 3
12
9 4
5
4 13
5 6
10
14
7
15
11 8
C External occipital protuberance Trapezius Fig .43 .7 The occipital bone . A, External surface . Key: 1, highest nuchal line;
Rectus capitis posterior minor Highest nuchal line 2, superior nuchal line; 3, inferior nuchal line; 4, hypoglossal canal; 5,
Superior nuchal line occipital condyle; 6, external occipital protuberance; 7, lambdoid margin;
Occipitofrontalis, 8, squamous part; 9, external occipital crest; 10, condylar canal; 11, foramen
occipital belly magnum . B, Internal surface . Key: 1, lambdoid margin; 2, internal occipital
Semispinalis capitis Sternocleidomastoid protuberance at ‘confluence of sinuses’; 3, lateral angle; 4, mastoid margin;
5, groove for sigmoid sinus; 6, jugular process; 7, jugular notch; 8, groove
Splenius capitis for inferior petrosal sinus; 9, cerebral fossa; 10, groove for transverse sinus;
11, internal occipital crest; 12, cerebellar fossa; 13, foramen magnum;
Obliquus superior
14, jugular tubercle; 15, margin of basilar part for articulation with body of
sphenoid . C, Muscle attachments . (A and B, With permission from Berkovitz
BKB, Moxham BJ 1994 Colour Atlas of the Skull . London: Mosby .)
Rectus capitis
posterior major Inferior nuchal line
Condylar canal
External
occipital crest
Rectus capitis lateralis
Jugular process
Alar ligament
Condylar fossa
Rectus capitis anterior Condyle
Hypoglossal canal
Longus capitis Pharyngeal tubercle
VERTEBRAL COLUMN


The vertebral column is a curved linkage of individual bones or verte-
brae (Fig. 43.9). A continuous series of vertebral foramina runs through
Upper part of squama the articulated vertebrae posterior to their bodies, and collectively con-
stitutes the vertebral canal, which transmits and protects the spinal cord
Line of union between upper and nerve roots, their coverings and vasculature (Fig. 43.10; see Fig.
and lower parts of squama 45.2). A series of paired lateral intervertebral foramina transmits the
spinal nerves and their associated vessels between adjacent vertebrae.
The linkages between the vertebrae include cartilaginous interbody
Lower part of squama joints and paired synovial facet (zygapophysial) joints, together with a
complex of ligaments and overlying muscles and fasciae. The muscles
Kerckring's centre directly concerned with vertebral movements and attached to the
column lie mainly posteriorly. Several large muscles producing major
spinal movements lie distant from the column and without direct
Lateral part attachment to it, e.g. the anterolateral abdominal wall musculature.
Movements of the column and the muscles concerned are described on
Basilar part page 745. The column as a whole receives its vascular supply and inner-
vation according to general anatomical principles, which are considered
below.
Fig .43 .8 The occipital bone of a newborn child, external surface . Parts of
Vertebral column morphology is influenced externally by mechani-
the chondrocranium that are still unossified are shown in blue .
cal and environmental factors and internally by genetic, metabolic and
hormonal factors. These all affect its ability to react to the dynamic
At birth, the occipital bone consists of four separate parts (Fig. 43.8) forces of everyday life, such as compression, traction and shear. These
– a basilar part, two lateral parts and a squamous part – all joined by dynamic forces can vary in magnitude and are much influenced by
cartilage and forming a ring around the foramen magnum. The squa- occupation, locomotion and posture.
mous and lateral parts fuse together from the second year. The lateral The adult vertebral column usually consists of 33 vertebral seg-


parts fuse with the basilar part during years three and four, but fusion ments. Each presacral segment (except the first two cervical) is sepa-
may be delayed until the seventh year. rated from its neighbour by a fibrocartilaginous intervertebral disc. The


Bones
715
34
RETPAHC
AA B C Atlas
Cervical Axis
vertebrae
1–7 Cervical
curvature
Vertebra
prominens
Thoracic
vertebrae
1–12 Intervertebral
discs
Thoracic
curvature
Intervertebral
Lumbar
foramen
vertebrae
1–5 Lumbar
curvature
Sacral
Sacrum promontory
Pelvic
curvature
Coccyx
Fig .43 .9 The vertebral column . A, Anterior aspect . B, Posterior aspect . C, Lateral aspect . (With permission from Waschke J, Paulsen F (eds), Sobotta
Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer . Copyright 2013 .)
functions of the column are to support the trunk, to protect the spinal Anterioraspect
cord and nerves, and to provide attachments for muscles. It is also an
important site of haemopoiesis throughout life. Its total length in
The anterior aspect of the column is formed by the anterior surfaces of
males is about 70 cm and in females about 60 cm. The intervertebral
the vertebral bodies and of the intervertebral discs (see Fig. 43.9A). It
discs contribute about one-quarter of this length in young adults,
has important anatomical relations at all levels and should be consid-
though there is some diurnal variation in this contribution. Approxi-
ered in continuity. It forms part of several clinically significant junc-
mately 8% of overall body length is accounted for by the cervical
tional or transitional zones, including the prevertebral/retropharyngeal
spine, 20% by the thoracic, 12% by the lumbar and 8% by the sacro-
zone of the neck, the thoracic inlet, the diaphragm and the pelvic inlet.
coccygeal regions. Although the usual number of vertebrae is 7 cervi-
The anterior aspect of the column is covered centrally by the anterior
cal, 12 thoracic, 5 lumbar, 5 sacral and 4 coccygeal, this total is subject
longitudinal ligament, which forms a fascial plane with the prevertebral
to frequent variability, and there have been reports of variation between


and endothoracic fascia and with the subperitoneal areolar tissue of the
32 and 35 bones. The demarcation of groups by their morphological
posterior abdominal wall. Infection and other pathological processes
characteristics may be blurred: thus there may be thoracic costal facets
may spread along this fascial plane.
on the seventh cervical vertebra, giving it the appearance of an extra
thoracic vertebra; lumbar-like articular processes may be found on the
Lateralaspect
lowest thoracic vertebra; or the fifth lumbar vertebra may be wholly or
partially incorporated into the sacrum. As a result of these changes in
transition between vertebral types, there may be 23–25 mobile presac- The lateral aspect of the vertebral column is arbitrarily separated from
ral vertebrae. the posterior by articular processes in the cervical and lumbar regions


BACk
716
5
NOITCES
Posterior arch of atlas
Axis
Spinal cord
Cervical spinal cord
Cauda equina
Anulus fibrosus
L3/4 disc
Nucleus pulposus
A B
Fig .43 .10 A sagittal magnetic resonance (MR) image of the cervical and upper thoracic (A) and lower thoracic and lumbar (B) spine .
and by transverse processes in the thoracic region (see Fig. 43.9C). Curvatures
Anteriorly, it is formed by the sides of vertebral bodies and interverte-
bral discs. The oval intervertebral foramina, behind the bodies and
Embryonic and fetal curvatures
between the pedicles, are smallest at the cervical and upper thoracic
The embryonic body appears flexed. It has primary thoracic and pelvic
levels, and increase progressively in size in the thoracic and upper
curves, which are convex dorsally. Functional muscle development leads
lumbar regions. The lumbosacral (L5/S1) intervertebral foramen is the
to the early appearance of secondary cervical and lumbar spinal curva-
smallest of the lumbar foramina (Fig. 43.11). The foramina permit
tures in the sagittal plane. The cervical curvature appears at the end of
communication between the lumen of the vertebral canal and the para-
the embryonic period, and reflects the development of function in the
vertebral soft tissues (a ‘paravertebral space’ is sometimes described),
muscles responsible for head extension, an important component of
which may be important in the spread of tumours and other pathologi-
the ‘grasp reflex’. Radiographic examination of human fetuses aged from
cal processes. The lateral aspects of the column have important ana-
8 to 23 weeks shows that the secondary cervical curvature is almost
tomical relations, some of which vary considerably between the two
always present. Lumbar flattening has also been identified as early as
sides.
the eighth week. Ultrasound investigations support the role of move-
ment in the development of these curvatures. The early appearance of
Posterioraspect the secondary curves is probably accentuated by postnatal muscular and
nervous system development at a time when the vertebral column is


The posterior aspect of the column is formed by the posterior surfaces highly flexible and is capable of assuming almost any curvature.
of the laminae and spinous processes, their associated ligaments, and
Neonatal curvatures
the facet joints (see Fig. 43.9B). It is covered by the deep muscles of the
In the neonate, the vertebral column has no fixed curvatures. It is par-
back.
ticularly flexible and, if dissected free from the body, it can easily be
Structural defects of the posterior bent (flexed or extended) into a perfect half-circle. A slight sacral cur-
vature can be seen, which develops as the sacral vertebrae ossify and
bony elements
fuse. The thoracic part of the column is the first to develop a relatively
Deformity and bony deficiency may occur at several sites within the fixed curvature, which is concave anteriorly. An infant can usually
posterior elements. The laminae may be wholly or partially absent, or support its head at 3 or 4 months, sit upright at around 9 months, and
the spinous process alone may be affected, with no abnormalities in will commence walking between 12 and 15 months. These functional
the overlying soft tissues (spina bifida occulta). A defect may occur changes exert a major influence on the development of the secondary
in the bone that joins the superior and inferior articular processes curvatures in the vertebral column and changes in the proportional size
(pars interarticularis): this condition is spondylolysis, and may be of the vertebrae, in particular in the lumbar region. The secondary
developmental or result from acute or fatigue fracture. If such defects lumbar curvature becomes important in maintaining the centre of
are bilateral, the column becomes unstable at that level, and forward gravity of the trunk over the legs when walking starts, and thus changes
displacement of that part of the column above (cranial to) the defects in body proportions exert a major influence on the subsequent shape
may occur: this is spondylolisthesis (Fig. 43.12). Abnormality of the of curvatures in the vertebral column.
laminar bone, or degenerative changes in the facet joints, may also lead
Adult curvatures
to similar displacement in the absence of pars defects. The deformity


of the vertebral canal resulting from severe spondylolisthesis may lead In adults, the cervical curve is a lordosis (convex forwards), and the least
to neural compression and subsequent damage (Fig. 43.13). Much marked. It extends from the atlas to the second thoracic vertebra, with
more rarely, bony defects may occur elsewhere in the posterior ele- its apex between the fourth and fifth cervical vertebrae. Sexual dimor-
ments, e.g. in the pedicles. phism has been described in the cervical curvatures. The thoracic curve
Detailed anatomical relations of all aspects of the vertebral column is a kyphosis (convex dorsally). It extends between the second and the
at the various levels are best appreciated by the study of horizontal eleventh and twelfth thoracic vertebrae, and its apex lies between
(axial) sections and images (see Figs 43.47B and 43.72). the sixth and ninth thoracic vertebrae. This curvature is caused by the


34
RETPAHC
Back
Fig .43 .11 A sagittal MR image of the lumbar spine showing the L5–S1
intervertebral foramen (neuroforamen) and a pathologically narrowed L4–5
intervertebral foramen (arrow) . This narrowing, known as lumbar foraminal
stenosis, results in leg pain in an L4 sensory distribution .
A
B
Fig .43 .13 (A) Sagittal and (B) axial MR images of a degenerative
spondylolisthesis at L4–5 . This condition is accompanied by massive
superior articular facet hypertrophy and subsequent critical central and
lateral recess stenosis (arrowheads) .
Fig .43 .12 A sagittal computed tomographic (CT) image of the lumbar
spine showing the left side of an isthmic spondylolisthesis resulting from
bilateral fractures of the pars interarticularis (arrow) .
716.e1


Bones
717
34
RETPAHC
increased posterior height of the thoracic vertebral bodies. The lumbar
A
curve is also a lordosis. It has a greater magnitude in females and
extends from the twelfth thoracic vertebra to the lumbosacral angle; Precentral branches
there is an increased convexity of the last three segments as a result of
the greater anterior height of the intervertebral discs and some posterior
Lumbar artery
wedging of the vertebral bodies. Its apex is at the level of the third
lumbar vertebra. The pelvic curve is concave anteroinferiorly and
involves the sacrum and coccygeal vertebrae. It extends from the lum-
bosacral junction to the apex of the coccyx. Dorsal branch
The presence of these curvatures means that the cross-sectional Spinal artery
profile of the trunk changes with spinal level. The anteroposterior diam-
eter of the thorax is much greater than that of the lower abdomen. In Spinal artery
the normal vertebral column, there are well-marked curvatures in the Postcentral
sagittal plane and no lateral curvatures other than in the upper thoracic branch
region, where there is often a slight lateral curvature, convex to the right
in right-handed persons, and to the left in the left-handed. Compensa-
Radicular
tory lateral curvature may also develop to cope with pelvic obliquity,
(neural)
such as that imposed by inequality of leg length. The sagittal curvatures branch
are present in the cervical, thoracic, lumbar and pelvic regions (see Fig.
43.9). These curvatures have developed with rounding of the thorax and
pelvis as an adaptation to bipedal gait.
Vertebralcolumnintheelderly
In older people, age-related changes in the structure of bone lead to
broadening and loss of height of the vertebral bodies. These changes
are more severe in females. The bony changes in the vertebral column Prelaminar branch Postlaminar branch
are accompanied by changes in the collagen content of the discs and
by decline in the activity of the spinal muscles. This leads to progressive B
decline in vertebral column mobility, particularly in the lumbar spine.


The development of a ‘dowager’s hump’ in the mid-thoracic region in
females, caused by age-related osteoporosis, increases the thoracic
kyphosis and cervical lordosis. Overall, these changes in the vertebral
column lead directly to loss of total height in the individual.
As discs desiccate, there is often a straightening of the cervical spine
and development of subsequent cervical kyphosis. This, coupled with
narrowing of the spinal canal, can lead to increased risk of neurological
damage of the cervical spinal cord, in addition to pain.
In mid-lumbar vertebrae, the width of the body increases with age.
In men there is a relative decrease of posterior to anterior body height,
while in both sexes anterior height decreases relative to width. Twomey
et al (1983) observed a reduction in bone density of lumbar vertebral
bodies with age, principally as a result of a reduction in transverse
trabeculae (more marked in females as a result of postmenopausal
osteoporosis), which was associated with increased diameter and
Anastomosis
increasing concavity in their juxtadiscal surfaces (end-plates).
Other changes affect the vertebral bodies. Osteophytes (bony spurs)
may form from the compact cortical bone on the anterior and lateral
surfaces of the bodies. Although individual variations occur, these
Postcentral branch
changes appear in most individuals from 20 years onwards. They are
most common on the anterior aspect of the body and never involve the Fig .43 .20 The arterial supply to the vertebrae and the contents of the
ring epiphysis. Osteophytic spurs are frequently asymptomatic but may vertebral canal . A, The branching pattern of the lumbar segmental
result in diminished movements within the spine. arteries . B, Arterial anastomoses between postcentral branches of spinal
arteries within the vertebral canal .
Vascularsupplyandlymphaticdrainage
muscles and skin. There is free anastomosis between these dorsal articu-
Arteries
lar and soft tissue branches, extending over several segments (Boelderl
The vertebral column, its contents and its associated soft tissues all et al 2002, Crock and Yoshizawa 1976). At cervical and sacral levels, the


receive their arterial supply from derivatives of dorsal branches of the longitudinally running arteries described above have direct spinal
embryonic intersegmental somatic arteries (see Fig. 13.13). The named branches. The spinal branches are the main arteries of supply to all bony
artery concerned depends on the level of the column. These interseg- elements of the vertebrae and to the dura and epidural tissues, and also
mental vessels persist in the thoracic and lumbar regions as the poste- contribute to the supply of the spinal cord and nerve roots via radicular
rior intercostal and lumbar arteries (Figs 43.14–43.16). In the cervical branches. As they enter the vertebral canal, the spinal arteries divide
and sacral regions, longitudinal anastomoses between the intersegmen- into postcentral, prelaminar and radicular branches. The postcentral
tal vessels persist as longitudinal vessels, which themselves give spinal branches, which are the main nutrient arteries to the vertebral bodies
branches to the vertebral column. In the neck, the postcostal anasto- and to the periphery of the intervertebral discs, anastomose beneath the
mosis becomes most of the vertebral artery, while the post-transverse posterior longitudinal ligament with their fellows above and below, as
anastomosis forms most of the deep cervical artery (Figs 43.17–43.19). well as across the midline (Fig. 43.20B). This anastomosis also supplies
The ascending cervical artery and the lateral sacral artery are persistent the anterior epidural tissues and dura. The majority of the vertebral
parts of the precostal anastomosis. arch, the posterior epidural tissues and dura, and the ligamentum
In the thorax and abdomen, the primitive arterial pattern is retained flavum are supplied by the prelaminar branches and their anastomotic
by the paired branches of the descending aorta, which supply the ver- plexus on the posterior wall of the vertebral canal. (For further reading
tebral column (Fig. 43.20A; see Fig. 43.14). On each side, the main on the arterial supply and venous drainage of the vertebral column and


trunk of the artery (posterior intercostal or lumbar) passes around the spinal cord, see Crock (1996) and Parke et al (2011).)
vertebral body, giving off primary periosteal and equatorial branches to
the body, and then a major dorsal branch. The latter gives off a spinal Veins
branch that enters the intervertebral foramen, before itself supplying Veins of the vertebral column form intricate plexuses along the entire
the facet joints, the posterior surfaces of the laminae and the overlying column, external and internal to the vertebral canal (Fig. 43.21) (Groen


34
RETPAHC
Back
IA PCB IA ACB
T6
L2
PCB
DB
NB
SB
DB IB
ALB
Fig .43 .14 A vertical radiograph of a section through T6 of a specimen
from a 6-year-old child injected with barium sulphate . The intercostal PLB
arteries (IA) give rise to dorsal branches (DB) that provide spinal branches
to the vertebral canal and posterior branches to the arch and dorsal
musculature . The posterior central branches (PCB) are well shown as they
send vessels into the vertebral body . Fine anterior central and anterior Fig .43 .16 A vertical radiograph of a section through a lumbar vertebra of
laminar and posterior laminar vessels can be seen . Note the neurocentral a 6-year-old child injected with barium sulphate . The vascularity of the
synchondrosis . (With permission from Parke WW, Bono CM, Garfin SR lumbar vertebra may be regarded as the archetypal pattern from which
2011 Applied anatomy of the spine . In: Herkowitz HN, Garfin SR, Eismont other regions evolved variations . The segmental lumbar artery gives rise
FJ, et al (eds) Rothman-Simeone The Spine, 6th edition . Saunders, to numerous anterior central branches (ACB) that penetrate the cortical
Elsevier .) bone of the body . The spinal branch (SB) sends prominent posterior
central branches (PCB) to the dorsum of the body, whereas the dorsal
branch (DB) supplies the anterior (ALB) and posterior (PLB) laminar
branches . Neural branches (NB) follow the nerve roots to the cord . In this
section, the arteria radicularis magna is seen as a neural branch on the
right side . Other abbreviations: IA, intercostal arteries; IB, intercostal
branches . (With permission from Parke WW, Bono CM, Garfin SR 2011
T 10 Applied anatomy of the spine . In: Herkowitz HN, Garfin SR, Eismont FJ,
et al (eds) Rothman-Simeone The Spine, 6th edition . Saunders, Elsevier .)
PCB
Arm
L2
Fig .43 .15 An anteroposterior arteriogram of the lower thoracic and upper


lumbar vertebrae in a 6-year-old child injected with barium sulphate . The
interlocking anastomotic pattern formed by the posterior central branches
(PCB) and the manner in which four branches converge over the centre of
the dorsum of the body of each vertebra are well shown . The arteria
radicularis magna (Arm), which forms a major contribution to the anterior
spinal artery of the cord, can be seen arising at L2 . (With permission from
Parke WW, Bono CM, Garfin SR 2011 Applied anatomy of the spine . In:
Herkowitz HN, Garfin SR, Eismont FJ, et al (eds) Rothman-Simeone The
Spine, 6th edition . Saunders, Elsevier .)
717.e1


5
NOITCES
BACk
1 ACB
2
10
VA
3
C4
4
C1
SB
5
C2 6 PCB
PLB
DC
C3
7 Fig .43 .18 A vertical radiograph of a section through the fourth cervical
vertebra of a 6-year-old child injected with barium sulphate . The deep
cervical artery (DC) provides the posterior laminar branches (PLB) .
Vertebral arteries show numerous anastomoses with other cervical
arteries and send spinal branches (SB) that form posterior central
8
11 branches (PCB) of the body and anterior laminar branches of the arch .
Anterior central branches (ACB) may arise independently from the
vertebral arteries (VA) . (With permission from Parke WW, Bono CM,
9
Garfin SR 2011 Applied anatomy of the spine . In: Herkowitz HN, Garfin
A
SR, Eismont FJ, et al (eds) Rothman-Simeone The Spine, 6th edition .
Saunders, Elsevier .)
1
10
3
6 5
VA
11
B
DC
Fig .43 .17 A, The arterial supply to the bodies of the upper cervical
vertebrae and the odontoid process . Numerical designations apply to the
same structures in B . Key: 1, meningeal artery in hypoglossal canal;
2, occipital artery; 3, apical arcade of odontoid process; 4, ascending
pharyngeal artery giving collateral branch beneath anterior arch of atlas;
CC
5, posterior ascending artery; 6, anterior ascending artery; 7, precentral
and postcentral arteries to typical cervical vertebral body; 8, anterior T1
spinal plexus; 9, medullary branch of vertebral artery: radicular,
prelaminar, and meningeal branches are also found at each level; 10,
collateral to ascending pharyngeal artery passing rostral to anterior arch
of atlas; 11, left vertebral artery . (With permission from Parke WW, Bono
CM, Garfin SR 2011 Applied anatomy of the spine . In: Herkowitz HN, IC


Garfin SR, Eismont FJ, et al (eds) Rothman-Simeone The Spine, 6th
edition . Saunders, Elsevier .) Fig .43 .19 An arteriogram of the cervical and upper thoracic regions of
the 6-year-old spine seen in Figures 42 .16 and 42 .18 . The vertebral artery
(VA) and deep cervical branch (DC) of the costocervical trunk (CC) supply
segmental branches to each vertebra . The costocervical artery also
typically supplies T1 and T2, but in this case T2 receives a high
intercostal (IC) branch on the left side . (With permission from Parke WW,
Bono CM, Garfin SR 2011 Applied anatomy of the spine . In: Herkowitz
HN, Garfin SR, Eismont FJ, et al (eds) Rothman-Simeone The Spine, 6th
edition . Saunders, Elsevier .)
717.e2


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5
NOITCES
Anterior internal vertebral Basivertebral Posterior longitudinal Anterior external with vertebral veins, occipital and sigmoid sinuses, the basilar plexus,
venous plexus vein ligament vertebral venous plexus the venous plexus of the hypoglossal canal and the condylar emissary
veins.
Basivertebral veins
The basivertebral veins are paired valveless veins that drain the pars
spongiosa of the vertebral bodies into the internal and external verte-
bral venous plexuses. In each segment, they emerge horizontally from
foramina in the vertebral bodies. Posteriorly, they drain into the trans-
verse branches of the anterior internal vertebral plexuses. Anteriorly,
they drain directly into the anterior external vertebral venous plexus.
The basivertebral veins enlarge in advanced age.
Intervertebral veins
Branches of the anterior internal plexuses drain into retrocorporal veins
that join the posterior internal venous plexuses to form intervertebral
veins. As their name suggests, these veins accompany the spinal nerves
through intervertebral foramina; they drain in craniocaudal sequence
into the vertebral, posterior intercostal, lumbar and lateral sacral veins.
Upper posterior intercostal veins may drain into the caval system via
brachiocephalic veins, whereas the lower intercostals drain into the
azygos system. Lumbar veins are joined longitudinally in front of the
transverse processes by the ascending lumbar veins, in which they may
terminate. Alternatively, they may proceed around the vertebral bodies
to drain into the inferior vena cava. Whether the basivertebral or
intervertebral veins contain effective valves is uncertain but experimen-
Posterior external Posterior internal Intervertebral Ascending tal evidence strongly suggests that their blood flow can be reversed
vertebral venous plexus vertebral venous plexus vein lumbar vein (Batson 1957). This may explain how pelvic neoplasms, e.g. carcinoma
Fig .43 .21 The venous drainage of the vertebral column . Note that the of the prostate, may metastasize in vertebral bodies: the cells spread
basivertebral vein is shown beneath (i .e . anterior to) the posterior into the internal vertebral plexuses via their connections with the pelvic


longitudinal ligament . (With permission from Waschke J, Paulsen F (eds), veins when blood flow is temporarily reversed by raised intra-abdominal
Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer . pressure or postural alterations (Pearce 2006).
Copyright 2013 .)
Lymphatic drainage
Little is known in detail about the lymphatic drainage of the vertebral
et al 2004). Both groups are devoid of valves, anastomose freely with
column and its associated soft tissues. In general, deep lymphatic
each other, and join the intervertebral veins. Interconnections are
vessels tend to follow the arteries. The cervical vertebral column drains
widely established between these plexuses and longitudinal veins early
to deep cervical nodes, the thoracic to (posterior) intercostal nodes, and
in fetal life. When development is complete, the plexuses drain into the
the lumbar column to lateral aortic and retro-aortic nodes. The pelvic
caval and azygos/ascending lumbar systems via named veins that
part of the column drains to lateral sacral and internal iliac nodes.
accompany the arteries described above.
The veins also communicate with cranial dural venous sinuses and
Innervation
with the deep veins of the neck and pelvis. The venous complexes
associated with the vertebral column can dilate considerably, and can
form alternative routes of venous return in patients with major venous The innervation of the vertebral column and its associated soft tissues
obstruction in the neck, chest or abdomen. The absence of valves allows has been studied in greatest detail in the lumbar region (see Fig. 43.61).
pathways for the wide and sometimes paradoxical spread of malignant The account given here relies particularly on the work of Bogduk
disease and sepsis. Pressure changes in the body cavities are transmitted (2005), to whose textbook on the lumbosacral spine the interested
through these venous plexuses and thus to the cerebrospinal fluid, reader is referred. See also the work of Groen et al (1990).
though the cord itself may be protected from such congestion by valves Innervation is derived from the spinal nerves where they branch, in
in the small veins that drain from the cord into the internal vertebral and just beyond the intervertebral foramina. There is an input from the


plexus. sympathetic system either via grey rami communicantes or directly from
thoracic sympathetic ganglia. The branches of the spinal nerve con-
External vertebral venous plexuses cerned are the dorsal ramus and the recurrent meningeal or sinuverte-
The external vertebral venous plexuses are anterior and posterior. They bral nerves (usually more than one at each level) (see Fig. 45.7). The
anastomose freely, and are most developed in the cervical region. Ante- dorsal ramus branches to supply the facet joints, periosteum of the
rior external plexuses are anterior to the vertebral bodies, communicate posterior bony elements, overlying muscles and skin. The exact origin
with basivertebral and intervertebral veins, and receive tributaries from and branching pattern of the sinuvertebral nerves is controversial, but
vertebral bodies. Posterior external plexuses lie posterior to the vertebral they may be best considered as recurrent branches of the ventral rami.
laminae and around spines and transverse and articular processes. They They receive the sympathetic input described above, then re-enter the
anastomose with the internal plexuses and join the vertebral, posterior intervertebral foramina to supply the structures that form the walls of
intercostal and lumbar veins. the vertebral canal, the dura and epidural soft tissues. Their subsequent
course is described on page 767.
Internal vertebral venous plexuses
The internal vertebral venous plexuses are embedded in epidural fat,
supported by a network of collagenous fibres (Chaynes et al 1998). VERTEBRAE: GENERAL FEATURES
These thin-walled channels receive tributaries from the bones, red bone
marrow and spinal cord. (For the venous drainage of the spinal cord, A typical vertebra has a ventral body; a dorsal vertebral (neural) arch,
see p. 770 and Fig. 45.14.) They form a denser network than the external extended by lever-like processes; and a vertebral foramen, which
plexuses and are arranged vertically as four interconnecting longitudi- is occupied in life by the spinal cord, meninges and their vessels
nal vessels: two anterior and two posterior. (Fig. 43.22).


The anterior internal plexuses are large plexiform veins on the pos- Opposed surfaces of adjacent bodies are bound together by interver-
terior surfaces of the vertebral bodies and intervertebral discs. They tebral discs of fibrocartilage. The complete column of bodies and discs
flank the posterior longitudinal ligament, beneath which they are con- forms the strong but flexible central axis of the body and supports the
nected by transverse vessels into which the large basivertebral veins full weight of the head and trunk. It also transmits even greater forces
open. The posterior internal plexuses, on each side in front of the ver- generated by muscles attached to it directly or indirectly. The foramina
tebral arches and ligamenta flava, anastomose with the posterior exter- form a vertebral canal for the spinal cord, and between adjoining neural
nal plexuses via veins that pass through and between the ligaments. The arches, near their junctions with vertebral bodies, intervertebral
internal plexuses interconnect by venous rings near each vertebra. foramina transmit mixed spinal nerves, smaller recurrent nerves, and
Around the foramen magnum, they form a dense network connecting blood and lymphatic vessels.


Bones
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RETPAHC
shallower than the inferior one (see Fig. 43.23). When vertebrae articu-
late by the intervertebral disc and facet joints, these adjacent vertebral
notches contribute to an intervertebral foramen. The complete peri-
meter of an intervertebral foramen consists of the notches, the dorso-
1
lateral aspects of parts of adjacent vertebral bodies and the intervening
2 disc, and the capsule of the synovial facet joint (see Fig. 43.25). The
laminae are directly continuous with the pedicles. They are vertically
7 flattened and curve dorsomedially.
Lateral to the spinous processes, vertebral grooves contain the deep
3 dorsal muscles. At cervical and lumbar levels, these grooves are shallow
and mainly formed by laminae. In the thoracic region, they are deeper,
8
broader and formed by the laminae and transverse processes. The
4 laminae are broad for the first thoracic vertebra and narrow for the
second to seventh, then broaden again from the eighth to eleventh, but
5 9 become narrow thereafter down to the third lumbar vertebra.
The spinous process (vertebral spine) projects dorsally and often
caudally from the junction of the laminae. Spines vary considerably in
size, shape and direction. They lie approximately in the median plane
and project posteriorly, although in some individuals a minor deflec-
6
10 tion of the processes to one side may be seen. The spines act as levers
for muscles that control posture and active movements (flexion/
Fig .43 .22 The fourth thoracic vertebra, superior aspect . Key: 1, bone
extension, lateral flexion and rotation) of the vertebral column.
derived from anular epiphysis; 2, vertebral body – bone derived from
The paired superior and inferior articular processes (zygapophyses)
centrum; 3, pedicle; 4, superior articular facet; 5, transverse process;
arise from the vertebral arch at the pediculolaminar junctions. The
6, spinous process; 7, vertebral body – bone derived from neural arch;


8, vertebral foramen; 9, costal facet; 10, lamina . superior processes project cranially, bearing dorsal facets that may also
have a lateral or medial inclination, depending on level. Inferior pro-
cesses run caudally with articular facets directed ventrally, again with a
Superior vertebral notch Superior articular facet medial or lateral inclination that depends on vertebral level. Articular
processes of adjoining vertebrae thus contribute to the synovial zygapo-
Body Pedicle Lamina
physial or facet joints, and form part of the posterior boundaries of the
intervertebral foramina. These joints permit limited movement between
Cortical bone
vertebrae; mobility varies considerably with vertebral level.
Transverse processes project laterally from the pediculolaminar junc-
Cancellous tions as levers for muscles and ligaments, particularly those concerned
bone in rotation and lateral flexion. In the cervical region, the transverse
processes are anterior to the articular processes, lateral to the pedicles
Spinous
and between the intervertebral foramina. In the thoracic region, they
process
are posterior to the pedicles, considerably behind those of the cervical
Basivertebral foramen
and lumbar processes. In the lumbar region, the transverse processes
are anterior to the articular processes, but posterior to the intervertebral
Inferior vertebral notch
foramina. There is considerable regional variation in the structure and
Inferior articular facet length of the transverse processes. In the cervical region, the transverse
process of the atlas is long and broad, which allows the rotator muscles
Unossified cartilaginous area maximum mechanical advantage. Breadth varies little from the second
Fig .43 .23 A median sagittal section through a lumbar vertebra . (With to the sixth cervical vertebra, but increases in the seventh. In thoracic
permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human vertebrae, the first is widest, and breadth decreases to the twelfth, where
Anatomy, 15th ed, Elsevier, Urban & Fischer . Copyright 2013 .) the transverse elements are usually vestigial. The transverse processes
become broader in the upper three lumbar vertebrae, and diminish in
the fourth and fifth. The transverse process of the fifth lumbar vertebra


The cylindroid vertebral body varies in size, shape and proportions is the most robust. It arises directly from the body and pedicle to allow
in different regions of the vertebral column. Its superior and inferior for force transmission to the pelvis through the iliolumbar ligament.
(discal) surfaces vary in shape from approximately flat (but not parallel) The thoracic transverse processes articulate with ribs, but at other
to sellar, with a raised peripheral smooth zone, formed from an ‘anular’ levels the mature transverse process is a composite of a ‘true’ transverse
epiphysial disc, within which the surface is rough. These differences in process and an incorporated costal element. Costal elements develop
texture reflect variations in the early structure of intervertebral discs. In as basic parts of neural arches in mammalian embryos, but become
the horizontal plane, the profiles of most bodies are convex anteriorly, independent only as thoracic ribs. Elsewhere, they remain less devel-
but concave posteriorly where they complete the vertebral foramen. oped and fuse with the ‘transverse process’ of descriptive anatomy (see
Most sagittal profiles are concave anteriorly but flat posteriorly. Small Fig. 44.11).
vascular foramina appear on the front and sides, and posteriorly there Vertebrae are internally trabecular and have an external shell of
are small arterial foramina and a large irregular orifice (sometimes compact bone perforated by vascular foramina (see Fig. 43.23). The
double) for the exit of basivertebral veins (Fig. 43.23). The adult verte- shell is thin on the superior and inferior body surfaces but thicker in
bral body is not coextensive with the developmental centrum but the arch and its processes. The trabecular interior contains red bone
includes parts of the neural arch posterolaterally. marrow and one or two large ventrodorsal canals that contain the
Viewed anteriorly, there is a cephalocaudal increase in vertebral body basivertebral veins. Pubertal adolescents have higher trabecular bone
width from the second cervical to the third lumbar vertebra, which density than prepubertal children.
is associated with an increased load-bearing function. The increase is Sexual dimorphism in vertebrae has received little attention, but


linear in the neck but not in the thoracic and lumbar regions. There is Taylor and Twomey (1984) have described radiological differences in
some variation in size of the last two lumbar bodies, but thereafter adolescent humans and have reported that female vertebral bodies have
width diminishes rapidly to the coccygeal apex. In the two lowest a lower ratio of width to depth. Vertebral body diameter has also been
lumbar vertebrae, there is an inverse relation between the areas of the used as a basis for sex prediction in the analysis of skeletal material
upper and lower surfaces of the bodies and the size of the pedicles and (MacLaughlin and Oldale 1992).
transverse processes.
On each side, the vertebral arch has a vertically narrower ventral part
Vertebralcanal
– the pedicle – and a broader lamina dorsally. Paired transverse, supe-
rior and inferior articular processes project from their junctions. There
is a median dorsal spinous process. The vertebral canal (Fig. 43.24) extends from the foramen magnum to
Pedicles are short, thick, rounded dorsal projections from the supe- the sacral hiatus, and follows the vertebral curves. In the cervical and
rior part of the body at the junction of its lateral and dorsal surfaces; lumbar regions, which exhibit free mobility, it is large and triangular,
the concavity formed by the curved superior border of the pedicle is but in the thoracic region, where movement is less, it is small and


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NOITCES
circular. These differences are matched by variations in the diameter of pedicles, face anterolaterally. External to them, and oriented in the same
the spinal cord and its enlargements. In the lumbar region, the vertebral direction, is a transverse process. The thoracic and lumbar intervertebral
canal decreases gradually in size between L1 and L5, with a greater rela- foramina face laterally and their transverse processes are posterior. In
tive width in the female. addition, the anteroinferior boundaries of the first to tenth thoracic
For clinical purposes, it is useful to consider the vertebral canal as foramina are formed by the articulations of the head of a rib and the
having three zones. These are a central zone, between the medial capsules of double synovial joints (with the demifacets on adjacent
margins of the facet joints, and two lateral zones, beneath the facet vertebrae and the intra-articular ligament between the costocapitular
joints and entering the intervertebral foramina. Each lateral zone, which ridge and the intervertebral symphysis). Lumbar foramina lie between
passes into and just beyond the intervertebral foramen, can be further the two principal lines of vertebral attachment of psoas major. The walls
subdivided into subarticular (lateral recess), foraminal and extraforami- of each foramen are covered throughout by fibrous tissue, which is in
nal regions (MacNab and McCulloch 1990). The lateral zone thus turn periosteal (though the presence of a true periosteum lining the
described forms the canal of the spinal nerve (the radicular or ‘root’ vertebral canal is controversial: Newell (1999)), perichondrial, anular
canal). The central zone of the canal is a little narrower than the radio- and capsular. The more lateral parts of the foramina may be crossed at
logical interpedicular distance if the lateral recess is considered to be a variable level by narrow fibrous bands, the transforaminal ligaments
part of the radicular canal rather than part of the central zone. (for detail of these ligaments, see Bogduk (2005)). The true foramen is


the foraminal region of the canal of the spinal nerve (the radicular or
Spinal stenosis
‘root’ canal). A foramen contains a segmental mixed spinal nerve and
Narrowing (stenosis) of the vertebral canal may occur at single or mul- its sheaths, from two to four recurrent meningeal (sinuvertebral) nerves,
tiple spinal levels, and mainly affects the lumbar and cervical regions. variable numbers of spinal arteries, and plexiform venous connections
Stenosis may affect the central canal and the ‘root canals’ either together between the internal and external vertebral venous plexuses. These
or separately. There is a developmental form of the condition that structures, particularly the nerves, may be affected by trauma or one of
mainly affects the central canal but more commonly the stenosis is the many disorders that may affect tissues bordering the foramen. In
degenerative, and results from intervertebral disc narrowing and osteo- particular, nerve compression and irritation may be caused by interver-
arthritic changes in the facet joints. This latter combination is more tebral disc prolapse, or by bony entrapment as the size of the foramen
likely to narrow the intervertebral foramen and the ‘root canal’, even decreases (Fig. 43.26). This decrease may result from facet joint osteo-
though the sectional profile of the vertebral canal in affected lumbar arthritis, osteophyte formation, disc degeneration and degenerative
vertebrae typically changes from the shape of a bell to that of a trefoil. spondylolisthesis, all of which may lead to lateral or foraminal spinal
The lumbosacral intervertebral foramen, which is normally the smallest stenosis.
in the region, is particularly liable to such stenosis. Severe spinal steno-
sis may compress the spinal cord and compromise its arterial supply.
More localized ‘root canal’ stenosis will present with the clinical fea- CERVICAL VERTEBRAE
tures of spinal nerve compression, but without the tension signs that
characterize the stretching of nerve roots over a prolapsed disc. Ischae- The cervical vertebrae (Figs 43.27–43.28) are the smallest of the move-
mia of the nerves and roots may provoke more damage than the actual able vertebrae, and are characterized by a foramen in each transverse


physical compression of the neural tissue. process. The first, second and seventh have special features and will be
considered separately. The third, fourth and fifth cervical are almost
Intervertebralforamina identical, and the sixth, while typical in its general features, has minor
distinguishing features.
Intervertebral foramina are the principal routes of entry to and exit from
the vertebral canal, and are closely related to the main intervertebral Typicalcervicalvertebra
articulations. (Minor routes occur between the median, often partly
fused, margins of the ligamenta flava.) The same general arrangement A typical cervical vertebra (Figs 43.29–43.30) has a small, relatively
applies throughout the vertebral column, between the axis and sacrum, broad vertebral body. The pedicles project posterolaterally and the
although there are some quantitative and structural regional variations. longer laminae posteromedially, enclosing a large, roughly triangular
Because of their construction, contents and susceptibilities to multiple vertebral foramen; the vertebral canal here accommodates the cervical
disorders, the intervertebral foramina are loci of great biomechanical,
functional and clinical significance. The specializations cranial to the
axis and at sacral levels are described with the individual bones and
articulations. Anterior tubercle
The boundaries of a generalized intervertebral foramen (Fig. 43.25)
Atlas
are, anteriorly, from above downwards, the posterolateral aspect of the
superior vertebral body, the posterolateral aspect of the intervertebral
symphysis (including the disc), and a small (variable) posterolateral
part of the body of the inferior vertebra; superiorly, the compact bone
of the deep arched inferior vertebral notch of the vertebra above; infe-
Dens (root)
riorly, the compact bone of the shallow superior vertebral notch of the
vertebra below; and posteriorly, a part of the ventral aspect of the Axis
fibrous capsule of the facet synovial joint. Cervical intervertebral Intervertebral
foramina are distinct in having superior and inferior vertebral notches foramen
of almost equal depth, which, in accord with the direction of the
Down-turned
ventral lip
Pedicle Raised lateral
lip of body
Intervertebral Uncinate process


disc
Third to
seventh
Posterolateral aspect of Capsule of cervical Carotid tubercle
vertebral body vertebrae
facet joint
Transverse
Ligamentum process
flavum
Costal element
Fig .43 .25 The boundaries of an intervertebral foramen . Fig .43 .27 The cervical vertebrae (anterior aspect) .


34
RETPAHC
Back
FM
C1
C2
C4
C6
T1
T6
Fig .43 .26 Markedly reduced L3–4 foraminal volume secondary to
advanced disc degeneration resulting in bony neural entrapment of the L3
nerve (arrow) .
L1
L3
L5
S1
S4
A B C
Fig .43 .24 The vertebral canal in section . A, Sagittal view . B, Transverse
(axial) view . C, Coronal view . Abbreviation: FM, foramen magnum .
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RETPAHC
enlargement of the spinal cord. The pedicles attach midway between
the discal surfaces of the vertebral body, so the superior and inferior
vertebral notches are of similar depth. The laminae are thin and slightly
curved, with a thin superior and slightly thicker inferior border. The
spinous process (‘spine’) is short and bifid, with two tubercles that are
often unequal in size. The junction between lamina and pedicle bulges
laterally between the superior and inferior articular processes to form
an articular pillar (‘lateral mass’) on each side. The transverse process
1 is morphologically composite around the foramen transversarium. Its
dorsal and ventral bars terminate laterally as corresponding tubercles.
2 The tubercles are connected, lateral to the foramen, by the costal (or
intertubercular) lamella; these three elements represent morphologi-
3
cally the capitellum, tubercle and neck of a cervical costal element (see
4 Fig. 44.11). The attachment of the dorsal bar to the pediculolaminar
junction represents the morphological transverse process, and the
5
attachment of the ventral bar to the ventral body represents the capitel-
6 lar process. In all but the seventh cervical vertebra, the foramen trans-
versarium normally transmits the vertebral artery and vein and a branch
from the cervicothoracic ganglion (vertebral nerve).
The vertebral body has a convex anterior surface. The discal margin
gives attachment to the anterior longitudinal ligament. The posterior
surface is flat or minimally concave, and its discal margins give attach-
ment to the posterior longitudinal ligament. The central area displays
several vascular foramina, of which two are commonly relatively larger.
Fig .43 .28 A lateral radiograph of the cervical spine . Key: 1, C1 posterior These are the basivertebral foramina, which transmit basivertebral veins
tubercle; 2, C2 spinous process; 3, C3 inferior articular process; 4, C4 to the anterior internal vertebral plexus. The superior discal surface is


lamina; 5, C6 superior articular facet; 6, C6/7 facet (zygapophyseal) joint . saddle-shaped, formed by flange-like lips, uncinate processes, which
arise from most of the lateral circumference of the upper margin of the
vertebral body. Uncinate processes are rudimentary at birth and are
usually found on the third to seventh cervical vertebra in the adult. The
uncinate processes on the vertebra below articulate with the corre-
sponding bevelled surfaces on the inferior aspect of the vertebra above.
1 Whether uncovertebral joints are synovial joints has proved controver-
6
sial since their description by von Luschka in 1858; the demonstration
of synoviocytes in the lateral joint capsule tissue of elderly uncoverte-
2 7 bral joints suggests that they should be regarded as synovial joints
(Hartman 2014) (see Fig. 43.59). The inferior discal surface is also
concave; the concavity is produced mainly by a broad projection from
the anterior margin, which partly overlaps the anterior surface of the
3
intervertebral disc. The discal surfaces of cervical vertebrae are so shaped
8
in order to restrict both lateral and anteroposterior gliding movements
during articulation. The paired ligamenta flava extend from the superior
9 border of each lamina below to the roughened inferior half of the
4 anterior surfaces of the lamina above. The superior part of the anterior
surface of each lamina is smooth, like the immediately adjacent surfaces
of the pedicles, which are usually in direct contact with the dura mater
and cervical root sheaths to which they may become loosely attached.
The spinous process of the sixth cervical vertebra is larger and is often
5 not bifid.
The superior articular facets, flat and ovoid, are directed superopos-
teriorly, whereas the corresponding inferior facets are directed mainly
anteriorly, and lie nearer the coronal plane than the superior facets. In
children, facet joint angle decreases until 10 years of age and remains
Fig .43 .29 The fourth cervical vertebra, superior aspect . Key: 1, body;
unchanged thereafter (Kasai et al 1996). The dorsal rami of the cervical


2, posterior tubercle of transverse process; 3, pedicle; 4, lamina; 5, bifid
spinal nerves curve posteriorly, close to the anterolateral aspects of the
spinous process; 6, anterior tubercle of transverse process; 7, foramen
lateral masses, and may actually lie in shallow grooves, especially on
transversarium; 8, superior articular facet; 9, vertebral foramen .
the third and fourth pairs. The dorsal root ganglion of each cervical
spinal nerve lies between the superior and inferior vertebral notches of
adjacent vertebrae. The large anterior ramus passes posterior to the
vertebral artery, which lies on the concave upper surface of the costal
lamella; the concavity of the lamellae increases from the fourth to the
sixth vertebra. The fourth to sixth anterior tubercles are elongated and
rough for muscle attachment. The sixth, the carotid tubercle of Chas-
1 saignac, is the longest (Fig. 43.31). The carotid artery can be forcibly
5 compressed in the groove formed by the vertebral bodies and the larger
anterior tubercles, especially the sixth. The posterior tubercles are
6
rounded and more laterally placed than the anterior, and all but the
7 sixth are also more caudal; the sixth is at about the same level as the
anterior.
8
2
MuscleattachmentsThe ligamentum nuchae and numerous deep
3 extensors, including semispinalis thoracis and cervicis, multifidus, spi-
4 nales and interspinales, are all attached to the spinous processes. Tendi-
9
nous slips of scalenus anterior, longus capitis and longus colli are
attached to the fourth to sixth anterior tubercles. Splenius, longissimus
Fig .43 .30 The fourth cervical vertebra, lateral aspect . Key: 1, uncinate and iliocostalis cervicis, levator scapulae and scalenus posterior and
process; 2, body; 3, anterior tubercle of transverse process; 4, posterior medius are all attached to the posterior tubercles. Shallow anterolateral


tubercle of transverse process; 5, superior articular process; 6, lateral depressions on the anterior surface of the body lodge the vertical parts
mass; 7, lamina; 8, spinous process; 9, inferior articular process . of the longus colli.


34
RETPAHC
Back
Fig .43 .31 An axial CT showing the carotid tubercle of Chassaignac
(arrow) . This bony landmark is useful for identification of the C6 vertebra
by palpation . Also note the bifid spinous process of C6 .
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5
NOITCES
A
1 Anterior arch (end of first year)
2
Each lateral mass (seventh week)
8
3
4
9
B
Apex of dens (fifth–eighth year)
5
6 Bilateral centres for dens
10
(sixth month, intrauterine) Each half neural arch
11
(seventh or eighth week)
7 Under surface of body Body (fourth month, intrauterine)
(at puberty)
Fig .43 .32 The first cervical vertebra (atlas), superior aspect . Key:
1, anterior tubercle; 2, anterior arch; 3, outline of dens; 4, superior
articular facet, on lateral mass (bipartite facet in this specimen); 5, outline C
of transverse ligament; 6, groove for vertebral artery and C1 (beneath
bony overhang from lateral mass here); 7, posterior arch; 8, transverse
process; 9, foramen transversarium; 10, vertebral foramen; 11, posterior
tubercle .
(All at puberty)
Transverse process
OssificationCervical vertebrae ossify according to the standard ver-
tebral pattern described on page 756. Incomplete segmentation (‘block
vertebra’) is common in the cervical spine and most commonly involves Spinous process Mammillary process
the axis and third cervical vertebra. There is a general caudal to cranial Fig .43 .34 Ossification in the vertebral column . A, The atlas . B, The axis .
gradient in the growth of ossification centres and closure of synchon- C, Lumbar vertebra .
droses in the atlas and axis (Karwacki and Schneider 2012).
Atlas,C1 vertebrae; the remaining part of the transverse process consists of the
costal lamella. A small anterior tubercle is sometimes visible on the
The atlas, the first cervical vertebra (Fig. 43.32), supports the head. It anterior aspect of the lateral mass. The costal lamella is sometimes
is unique in that it fails to incorporate a centrum, whose expected posi- deficient, which leaves the foramen transversarium open anteriorly.
tion is occupied by the dens, a cranial protuberance from the axis. The


atlas consists of two lateral masses connected by a short anterior and a MuscleattachmentsThe superior oblique parts of longus colli are
longer posterior arch. The transverse ligament retains the dens against attached on each side of the anterior tubercle. The anterior surface of
the anterior arch. the lateral mass gives attachment to rectus capitis anterior. Rectus capitis
The transverse ligament divides the vertebral canal into two compart- posterior minor is attached just lateral to the posterior tubercle. Rectus
ments (Fig. 43.33). The anterior third (approximately) of the canal is capitis lateralis is attached to the transverse process superiorly, and
occupied by the dens. The posterior compartment is occupied by the obliquus capitis superior is located more posteriorly. Obliquus capitis
spinal cord and its coverings, and the cord itself takes up about half of inferior is attached laterally on the apex, below which are slips of levator
this space (i.e. the cord, like the dens, occupies one-third of the canal). scapulae, splenius cervicis and scalenus medius.
The anterior arch is slightly convex anteriorly, and carries a rough-
ened anterior tubercle to which is attached the anterior longitudinal OssificationThe atlas is commonly ossified from three centres (Fig.
ligament (which is cylindrical at this level). Its upper and lower borders 43.34). One appears in each lateral mass at about the seventh week,
provide attachment for the anterior atlanto-occipital membrane and gradually extending into the posterior arch where they unite between
diverging lateral parts of the anterior longitudinal ligament. The poste- the third and fourth years, usually directly but occasionally through a
rior surface of the anterior arch carries a concave, almost circular, facet separate centre. At birth, the anterior arch is fibrocartilaginous, and a
for the dens. separate centre appears about the end of the first year. This unites with
The lateral masses are ovoid, their long axes converging anteriorly. the lateral masses between the sixth and eighth years, the lines of union
Each bears a kidney-shaped superior articular facet for the respective extending across anterior parts of the superior articular facets. Occasion-
occipital condyle, which is sometimes completely divided into a larger ally, the anterior arch is formed by the extension and ultimate union


anterior and a smaller posterior part (Lang 1986). The inferior articular of centres in the lateral masses and sometimes from two lateral centres
facet of the lateral mass is almost circular and is flat or slightly concave. in the arch itself.
It is orientated more obliquely to the transverse plane than the superior The central part of the posterior arch may be absent and replaced by
facet, and faces more medially and very slightly backwards. On the fibrous tissue. Frequently, bony spurs arise from the anterior and pos-
medial surface of each lateral mass is a roughened area that bears vas- terior margins of the groove for the vertebral artery. These are sometimes
cular foramina and a tubercle for attachment of the transverse ligament. referred to as ponticles; they occasionally convert the groove into a
In adults, the distance between these tubercles is shorter than the trans- foramen, the arcuate foramen or posticus ponticus (Fig. 43.35), which
verse ligament itself, with a mean value of approximately 16 mm. may increase the risk of injury to the vertebral artery in surgical proce-
The posterior arch forms three-fifths of the circumference of the dures involving the C1 arch (Klimo et al 2007). More often, the foramen
atlantal ring. The superior surface bears a wide groove for the vertebral is incomplete superiorly. Rarely, the atlas may be wholly or partially
artery and venous plexus immediately behind, and is variably overhung assimilated into (fused with) the occiput.
by the lateral mass; the first cervical nerve intervenes. The flange-like
Axis,C2
superior border gives attachment to the posterior atlanto-occipital
membrane, and the flatter inferior border to the highest pair of liga-
menta flava. The posterior tubercle is a rudimentary spinous process, The axis, the second cervical vertebra (Figs 43.36–43.37), acts as an axle
roughened for attachment of the ligamentum nuchae. for rotation of the atlas and head around the strong dens (odontoid
The transverse processes are longer than those of all cervical verte- process), which projects cranially from the superior surface of the body.


brae except the seventh (see Fig. 43.27). They act as strong levers for The dens is conical in shape with a mean length of 15 mm in adults.
the muscles that make fine adjustments to keep the head balanced. It may be tilted a little, up to 14°, posteriorly or, less often, anteriorly
Maximum atlantal width varies from 74 to 95 mm in males and 65 to on the body of the axis; it may also tilt laterally up to 10°. The posterior
76 mm in females, and this affords a useful criterion for assessing sex surface bears a broad groove for the transverse ligament, which is
in human remains. The apex of the transverse process, which is usually covered in cartilage. The apex is pointed, and from this point arises
broad, flat and palpable between the mastoid process and ramus of the the apical ligament. The alar ligaments are attached to the somewhat
mandible, is homologous with the posterior tubercle of typical cervical flattened posterolateral surfaces above the groove for the transverse


34
RETPAHC
Back
Fig .43 .33 An axial MR image showing an intact transverse ligament
(arrow) .
Fig .43 .35 A lateral cervical radiograph demonstrating a posterior ponticle
that forms the roof of a tunnel over the vertebral artery (arrow) .
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RETPAHC
tebral notch, in which the large root sheath of the third cervical nerve
7
1 lies. The interarticular part of the pedicle is short and lies between the
relatively small inferior posterior articular process (which is located at
2 the pediculolaminar junction and bears a small anteriorly facing facet)
and the superior articular surface.
3 The transverse process is pointed, projects inferiorly and laterally,
4 and arises from the pediculolaminar junction and the lateral aspect of
8 the interarticular area of the pedicle. The rounded tip is homologous
with the posterior tubercle of a typical cervical vertebrae. The foramen
5 transversarium is directed laterally as the vertebral artery turns abruptly
9 laterally under the superior articular facet. Small anterior tubercles may
be present near the junction of the costal lamella with the body.
10
The laminae are thick and give attachment to the ligamenta flava.
11 The spinous process is large, with a bifid tip and a broad base, which
is concave inferiorly. The ligamentum nuchae is attached to the apical
notch.
MuscleattachmentsThe anterior surface of the body carries a deep
depression on each side for the attachment of the vertical part of longus
colli. Levator scapulae, scalenus medius and splenius cervicis are all
6 attached to the tips of the transverse processes, and the intertransverse
muscles are attached to their upper and lower surfaces. The lateral sur-
faces of the spinous process give origin to obliquus capitis inferior, and
Fig .43 .36 The second cervical vertebra (axis), superior aspect . Key: rectus posterior major is attached a little more posteriorly. The inferior
1, dens – attachment of apical ligament; 2, superior articular facet on concavity of the process receives semispinalis and spinalis cervicis, mul-
lateral mass; 3, dens – attachments of alar ligaments; 4, foramen tifidus more deeply, and the interspinales near the apex.
transversarium; 5, pedicle; 6, spinous process; 7, body; 8, transverse


process; 9, vertebral foramen; 10, inferior articular process; 11, lamina . ArterialsupplySmall branches arise mainly from the vertebral artery
at the level of the intervertebral foramen for the third cervical nerve and
form paired anterior and posterior longitudinal channels, branches of
which enter the dens near the base and near the apex. The anterior
channel also receives numerous twigs from nearby branches of the
1
external carotid artery via branches to longus colli and the ligaments of
the apex; hence avascular necrosis does not occur after fracture of the
2 base of the dens.
3 OssificationThe axis is ossified from five primary and two secondary
centres (see Fig. 43.34). The vertebral arch has two primary centres and
the centrum one, as in a typical vertebra. The former appear at about
the seventh or eighth week, and that for the centrum at about the fourth
4 9 or fifth month. The dens is largely ossified from bilateral centres,
appearing at about the sixth month and joining before birth to form a
10 conical mass, deeply cleft above by cartilage. This cuneiform cartilage
5
forms the apex of the odontoid process. A centre appears in it which
6
shows considerable individual variation in both time of appearance and
7 time of fusion to the rest of the dens; it most often appears between
11 five and eight years, but sometimes even later, fusing with the main
mass in about the twelfth year. The cartilage was thought to be part of
8 12 the cranial sclerotomal half of the first cervical segment or pro-atlas. It
has also been suggested that the apical centre for the dens is itself
Fig .43 .37 The second cervical vertebra (axis), lateral aspect . Key:
derived from the pro-atlas, which may also contribute to lateral atlantal
1, dens – attachment of alar ligament; 2, facet for anterior arch of atlas;
masses. The dens is separated from the body by a cartilaginous disc, the
3, groove for transverse ligament of atlas; 4, superior articular facet;
circumference of which ossifies while its centre remains cartilaginous
5, lateral mass; 6, divergent foramen transversarium; 7, body; 8, ventral


until old age; possible rudiments of adjacent epiphyses of atlas and axis
lip of body; 9, lamina; 10, spinous process; 11, inferior articular facet;
12, transverse process . may occur in the disc. A thin epiphysial plate is formed inferior to the
body around puberty.
Ossification may sometimes be incomplete. Thus the apical cunei-
form centre may fail to fuse with the dens, or the dens itself may fail
ligament. The anterior surface bears an ovoid articular facet for the
to fuse with the body, instead forming an os odontoideum (Fig. 43.38).
anterior arch of the atlas, and the surface is pitted by many vascular
This is likely to result from minor trauma in early childhood causing
foramina, which are most numerous near the apex.
disruption of the developing dens rather than being a congenital failure
The body consists of less compact bone than the dens. It is compos-
(Klimo et al 2007). Interposition of the transverse ligament may prevent
ite, and consists of the partly fused centra of the atlas and axis, and a
union of fractures through the base of the dens (Fig. 43.39). Hypoplasia
rudimentary disc (synchondrosis) between them, which usually remains
of the dens is usually accompanied by atlanto-occipital assimilation
detectable deep within the body of the axis throughout life. Large ovoid
and basilar invagination. Abnormalities of the dens are common, and
articular facets are present on either side of the dens at the junction of
can result in atlanto-axial subluxation. In some skeletal dysplasias there
the body and neural arch; they are flat or slightly convex for articulation
is abnormal ossification in which the dens ossifies separately and much
with the masses of the atlas. The facets lie in a plane anterior to the
later than the atlantal centrum. This is probably a result of abnormal
plane of the intercentral (Luschka) articulations, with which they are,
mobility in the cartilaginous anlage, and normal ossification may be
in part, homologous. The somewhat triangular, downward-projecting
restored if motion is prevented by surgical fusion.
anterior border gives attachment to the anterior longitudinal ligament.
Posteriorly, the lower border receives the posterior longitudinal liga-


Seventhcervicalvertebra,vertebra
ment and the membrana tectoria.
prominens,C7
The pedicles are stout, and the superior surface carries part of the
superior articular facet, which also projects laterally and downwards on
to the transverse process. The anterolateral surface is deeply grooved by The seventh cervical vertebra, the vertebra prominens (Fig. 43.40), has
the vertebral artery, running beneath the thin lateral part of the inferior a long spinous process that is visible at the lower end of the nuchal
surface of the superior articular facet, which can become quite thin. The furrow. It ends in a prominent tubercle for the attachment of the
inferior surface of each pedicle bears a deep, smooth inferior interver- ligamentum nuchae and the muscles detailed below. The thick and


34
RETPAHC
Back
Fig .43 .39 A sagittal CT scan reconstructed image of a type II odontoid
fracture (arrow) . These fractures involve the base of the dens and have a
high non-union rate .
Fig .43 .38 A sagittal CT scan reconstructed image demonstrating an os
odontoideum (arrow) .
723.e1


BACk
724
5
NOITCES
Costal facets
1 5
Complete circular facet above
6
7
Small semilunar facet below
8
2
9
3 10 Large semicircular facet above
Small semilunar facet below
4 Space for intervertebral disc
Large semicircular facet above
Fig .43 .40 The seventh cervical vertebra, superior aspect . Key: 1, body; Intervertebral foramen
2, superior articular facet; 3, inferior articular process; 4, spinous process;
5, uncinate process; 6, foramen transversarium (foramina are
asymmetrical in this specimen); 7, transverse process; 8, pedicle; Complete circular facet on body
No facet on transverse process
9, vertebral foramen; 10, lamina .
Facet joint
prominent transverse processes lie behind and lateral to the foramina
transversaria. The latter transmit vertebral veins but not the vertebral
artery, and each is often divided by a bony spicule. The costal lamella
is relatively thin and may be partly deficient. It is grooved superiorly Complete circular facet
for the anterior ramus of the seventh cervical nerve and usually carries on body, encroaching on pedicle
No facet on transverse process
a small and inconspicuous anterior tubercle. The posterior tubercle is Inferior articular processes
prominent. The suprapleural membrane is attached to the anterior of lumbar type
border of the transverse process.
The costal lamella of the transverse process may be separate as a
cervical rib. The foramina transversaria may be asymmetrical; some-
Fig .43 .41 The first, ninth, tenth, eleventh and twelfth thoracic vertebrae,
times one is absent if the costal lamella is undeveloped. lateral aspect .
MuscleattachmentsTrapezius, spinalis capitis, semispinalis tho-
racis, multifidus and interspinales all attach to the tubercle of the
spinous process. The anterior border of the transverse process receives 3
the attachment of scalenus minimus (pleuralis), when present. The first
pair of levatores costarum is attached to the transverse processes.
4


OssificationOssific centres for the costal processes appear about the 5
sixth month and join the body and transverse processes between the
fifth and sixth years; they may remain separate and grow anterolaterally 2
6
as cervical ribs. Separate ossific centres may, on occasion, also occur in
1
the costal processes of the fourth to sixth cervical vertebrae.
7
THORACIC VERTEBRAE
Thoracicvertebraeingeneral
8
All thoracic vertebral bodies display lateral costal facets and all but the
lowest two or three transverse processes also have facets (Fig. 43.41).
The facets articulate with the head of the rib (costocapitular facet) and
its tubercle (costotubercular facet), respectively.
The body is typically a waisted cylinder (Fig. 43.42) except where
Fig .43 .42 The fourth thoracic vertebra, lateral aspect . Key: 1, body;
the vertebral foramen encroaches, and transverse and anteroposterior
2, costocapitular demifacets; 3, superior articular facet; 4, transverse
dimensions are almost equal. On each side there are two costal facets
process; 5, costotubercular facet; 6, pedicle; 7, inferior articular process;
(which are really demifacets): the superior and usually larger pair at the 8, spinous process .
upper border are anterior to the pedicles, while the inferior pair at the
lower border are anterior to the vertebral notches. The vertebral foramen
(see Fig. 43.22) is small and circular, so the pedicles do not diverge as The bodies of upper thoracic vertebrae gradually change from cervi-
they do in cervical vertebrae; the thoracic spinal cord is smaller and cal to thoracic in type, and the lower change from thoracic to lumbar.
more circular than the cervical cord. The laminae are short, thick and The body of the first is typically cervical, its transverse diameter being
broad, and overlap from above downwards. The spinous process slants almost twice the anteroposterior; the second retains a cervical shape but


downwards. The thin and almost flat superior articular processes project its two diameters differ less. The third body is the smallest, and has a
from the pediculolaminar junctions and face posteriorly and a little convex anterior aspect unlike the flattened first and second thoracic
superolaterally. The inferior processes project down from the laminae vertebrae. The remaining bodies increase in size and, because of its
and their facets are directed forwards and a little superomedially. increased anteroposterior diameter, the fourth is typically ‘heart-shaped’.
The large, club-like transverse processes also project from the pedicu- The fifth to eighth increase their anteroposterior dimension but change
lolaminar junctions. Each passes posterolaterally and bears, near its tip, little transversely. These four, in transverse section, are asymmetrical,
anterior oval facets for articulation with the tubercle of the correspond- their left sides being flattened by pressure of the thoracic aorta. The rest
ing rib. increase more rapidly in all measurements, so that the body of the


Bones
725
34
RETPAHC
twelfth resembles that of a typical lumbar vertebra. These modifications
may contribute to the greater range of flexion–extension seen at the
cervical and lumbar ends of the thoracic vertebral column.
The anterior and posterior longitudinal ligaments are attached to the
borders of the bodies. The capsular and radiate ligaments of the cos-
tovertebral joints are attached around the margins of the costal facets. 1
The dimensions and angles of thoracic pedicles change progressively
from the upper thoracic spine distally: there is a successive caudal
increase in thickness. These changing relationships have a significant
bearing on the placement of pedicle screws in spinal surgery (Wood
2013). The superior vertebral notch is recognizable only in the first
thoracic vertebra, whereas the inferior notch is deep in all. Ligamenta
flava are attached at the upper borders and lower anterior surfaces of 2
the laminae. 7
Thoracic transverse processes shorten in caudal succession. In the
upper five or six vertebrae, the costal facets are concave and face antero-
8
laterally, and at lower levels the facets are flatter and face superolaterally
and slightly forwards. The costotransverse ligament is attached to the
3
anterior surface medial to the facet; the lateral costotransverse ligament
is attached to its tuberculated apex and the superior costotransverse
4 9
ligament is attached to its lower border.
Thoracic spines overlap from the fifth to the eighth vertebra, whose 5 10
spine is the longest and most oblique. Supraspinous and interspinous
ligaments are attached to the spines.
The first and ninth to twelfth 6
thoracic vertebrae
The first and ninth to twelfth thoracic vertebrae display additional atypi- Fig .43 .43 The first lumbar vertebra, superior aspect . Key: 1, body;
cal features. The first thoracic vertebra (see Fig. 43.41) resembles a cervi- 2, pedicle; 3, transverse process; 4, accessory process; 5, mammillary


cal vertebra in its body, both in shape and in the distinctive posterolateral process; 6, spinous process; 7, vertebral foramen; 8, superior articular
facet; 9, lamina; 10, inferior articular facet .
‘lipping’ that forms the anterior border of the superior vertebral notch.
There are circular superior costal facets for articulation with the whole
facet on the head of the first rib. The smaller, semilunar inferior facets
articulate with a demifacet on the head of the second rib. The upper
costal facet is often incomplete, in which case the first rib articulates OssificationThoracic vertebrae all ossify according to the standard
with the seventh cervical vertebra and the intervening disc. A small, vertebral pattern described on page 756.
deep depression often occurs below the facet. The long, thick spine is
horizontal and commonly as prominent as that of the seventh cervical
LUMBAR VERTEBRAE
vertebra. The ninth vertebra (see Fig. 43.41) often fails to articulate with
the tenth ribs, in which case the inferior demifacets are absent. The
Lumbarvertebraeingeneral
tenth thoracic vertebra (see Fig. 43.41) only articulates with the tenth
pair of ribs, so that superior facets only appear on the body. These are
usually large and semilunar, but are oval when the tenth ribs fail to The five lumbar vertebrae are distinguished by their large size and the
articulate with the ninth vertebra and intervening disc. The transverse absence of costal facets and transverse foramina. The body is wider
process may or may not bear a facet for the tubercle of the tenth rib. transversely (Fig. 43.43; see Fig. 43.47B). The vertebral foramen is tri-
The eleventh thoracic vertebra (see Fig. 43.41) articulates only with the angular, larger than at thoracic levels but smaller than at cervical levels.
heads of the eleventh ribs. The circular costal facets are close to the The pedicles are short. The spinous process is almost horizontal, quad-
upper border of the body and extend on to the pedicles. The small rangular and thickened along its posterior and inferior borders. The


transverse processes lack articular facets. The eleventh and twelfth tho- superior articular processes bear vertical concave articular facets facing
racic spinous processes are triangular, with blunt apices and a horizon- posteromedially, with a rough mammillary process on their posterior
tal lower and an oblique upper border. The twelfth thoracic vertebra borders (Fig. 43.44A). The inferior articular processes have vertical
(see Fig. 43.41) articulates with the heads of the twelfth ribs by circular convex articular facets that face anterolaterally. The transverse processes
facets somewhat below the upper border, spreading on to the pedicles. are thin and long, except on the more substantial fifth pair. A small
The body is large and the vertebra has some lumbar features. The trans- accessory process marks the posteroinferior aspect of the root of each
verse process is replaced by three small tubercles: the superior is largest, transverse process. The accessory and mammillary processes are linked
projects upwards and corresponds to a lumbar mammillary process, by a fine ligament, the mammillo-accessory ligament, which is some-
though it does not lie as close to the superior articular process; the times ossified, and beneath which runs the medial branch of the dorsal
lateral tubercle is the homologue of a transverse process; and the infe- primary ramus of the spinal nerve (Bogduk 2005).
rior is the homologue of a lumbar accessory process. The superior and Strong paired pedicles arise posterolaterally from each body near its
inferior processes are surprisingly long in some specimens. upper border. Superior vertebral notches are shallow and the inferior
A change in orientation of articular processes from thoracic to ones are deep. The laminae are broad and short, but do not overlap as
lumbar type usually occurs at the eleventh thoracic vertebra, but some- much as those of the thoracic vertebrae. The fifth spine is the smallest,
times at the twelfth or tenth. In the transitional vertebra the superior and its apex is often rounded and down-turned. Upper lumbar superior
articular processes are thoracic, and face posterolaterally, while the articular processes are further apart than inferior ones, but the differ-


inferior are transversely convex and face anterolaterally. The transitional ence is slight in the fourth and negligible in the fifth. The articular facets
vertebra marks the site of a sudden change of mobility from predomi- are reciprocally concave (superior) and convex (inferior), which allows
nantly rotational to predominantly flexion–extension. flexion, extension, lateral bending and some degree of rotation. There
are sex differences in the angle of inclination and depth of curvature of
MuscleattachmentsLongus colli arises from the upper three tho- the articular facets. The facets are sometimes asymmetrical.
racic vertebral bodies, lateral to the anterior longitudinal ligament, and Transverse processes, except the fifth, are anteroposteriorly com-
psoas major and minor arise from the sides of the twelfth near its lower pressed and project posterolaterally. The lower border of the fifth trans-
border. Upper and lower borders of the transverse processes provide verse process is angulated, and passes laterally and then superolaterally
attachment for the intertransverse muscles or their fibrous vestiges. The to a blunt tip; the whole process presents a greater upward inclination
posterior surfaces of the transverse processes provide attachment for than the fourth. The angle on the inferior border may represent the tip
the deep dorsal muscles, and levator costae is attached posteriorly on of the costal element and the lateral end the tip of the true transverse
the apex. Trapezius, rhomboid major and minor, latissimus dorsi, ser- process. The lumbar transverse processes increase in length from first
ratus posterior superior and inferior, and many deep dorsal muscles are to third and then shorten (Fig. 43.45). The fifth pair incline both
attached to the spines. Rotatores attach to the posterior aspects of the upwards and posterolaterally. The costal element is incorporated in the
laminae. mature transverse process.


BACk
726
5
NOITCES
A
Superior articular process
Body
5
Mammillary process
Transverse process
Pedicle
Spinous process
6
Inferior articular process
1 7
2
8
9
3
3
4 10
4
Fig .43 .45 An anteroposterior radiograph of the lumbosacral spine in a
5 22-year-old male . Key: 1, L3 inferior articular process; 2, L4 superior
articular process; 3, right sacroiliac joint; 4, ilium; 5, psoas lateral border;
6, L3 transverse process; 7, facet joint; 8, L4 pedicle; 9, L4 spinous
1
process; 10, anterior sacral foramen .
6
MuscleandfascialattachmentsUpper and lower borders of
lumbar bodies give attachment to the anterior and posterior longitudi-
2
nal ligaments. The upper bodies (three on the right, two on the left)
give attachments to the crura of the diaphragm lateral to the anterior
longitudinal ligament. Posterolaterally, psoas major is attached to the
upper and lower margins of all the lumbar bodies, and between them,
tendinous arches carry its attachments across their concave sides (see
Fig. 62.5). The posterior lamella of the thoracolumbar fascia, erectores
spinae, spinales thoracis, multifidi, interspinal muscles and ligaments,
and supraspinous ligaments are all attached to spinous processes. All
lumbar transverse processes present a vertical ridge on the anterior
surface, nearer the tip, which marks the attachment of the anterior layer
of the thoracolumbar fascia, and separates the surface into medial and
B
lateral areas for psoas major and quadratus lumborum respectively. The
middle layer of the fascia is attached to the apices of the transverse
Fig .43 .44 The lumbar spine . A, A typical lumbar vertebra, lateral aspect .
processes; the medial and lateral arcuate ligaments attach to the vertical
B, A lateral radiograph, 24-year-old male . Key: 1, L4 transverse process;


ridge on the anterior aspect of the first pair, and the iliolumbar ligament
2, L4 pedicle; 3, twelfth rib; 4, L2 superior articular facet; 5, L3 spinous
process; 6, L3/4 intervertebral foramen . attaches to the apices of the fifth pair. Posteriorly, the transverse pro-
cesses are covered by deep dorsal muscles, and fibres of longissimus
thoracis are attached to them and to their accessory processes. The
ventral lateral intertransverse muscles are attached to their upper and
lower borders, while the dorsal attach cranially to the accessory process
and caudally to the upper border of the transverse process. The mam-
On average, the adult spinal cord ends at the level of the middle
millary process, homologous with the superior tubercle of the twelfth
third of the body of the first lumbar vertebra, which means that the first
thoracic vertebra, gives attachment to multifidus and the medial inter-
lumbar vertebral foramen usually contains the conus medullaris. The
transverse muscle. The latter also attaches to the accessory process,
cord may terminate above or below this level (Saifuddin et al 1998)
which is sometimes difficult to identify.
(see Fig. 43.78 and Ch. 45); lower lumbar vertebral foramina contain
the cauda equina and spinal meninges (Fig. 43.46; see Fig. 43.10B). OssificationLumbar vertebrae ossify according to the standard ver-
Variation occurs in the sagittal and coronal dimensions of the lumbar
tebral pattern described on page 756 but also have two additional
vertebral canal, both within and between normal populations.
centres for the mammillary processes. A pair of scale-like epiphyses
The fifth lumbar vertebra (Fig. 43.47) has a massive transverse
usually appear on the tips of the costal elements of the fifth lumbar
process that is continuous with the whole of the pedicle and encroaches
vertebra (see Fig. 43.34C).
on the body. The body is usually the largest and markedly deeper ante-
riorly, so contributing to the lumbosacral angle.
Segmentation anomalies (sacralization) are considered below with SACRUM


the sacrum. The costal element of the first lumbar vertebra may form a
short lumbar rib, which articulates with the transverse process, but not The sacrum is a large, triangular fusion of five vertebrae and forms the
usually with the body, of the vertebra. posterosuperior wall of the pelvic cavity (Ch. 80), wedged between the


Bones
727
34
RETPAHC
Conus medullaris
Anulus fibrosus
Nucleus pulposus
Posterior longitudinal L4 roots converging to
ligament form spinal nerve
A B
Fig .43 .46 The lumbar spine . A, A midsagittal MR image . B, A sagittal MR image .
two hip (innominate) bones. Its blunted, caudal apex articulates with covered almost entirely by psoas major. The smooth area is grooved
the coccyx and its superior, wide base with the fifth lumbar vertebra at obliquely by the lumbosacral trunk. The rough area is for the lower
the lumbosacral angle. It is set obliquely and curved longitudinally, the band of the iliolumbar ligament, which lies lateral to the fifth lumbar
dorsal surface is convex, and the pelvic surface is concave; this ventral spinal nerve and to the anterior sacroiliac ligament.
curvature increases pelvic capacity. Between base and apex are dorsal,
pelvic and lateral surfaces and a sacral canal. In childhood, individual PelvicsurfaceThe anteroinferior pelvic surface (Fig. 43.49) is verti-
sacral vertebrae are connected by cartilage, and the adult bone retains cally and transversely concave, but the second sacral body may produce
many vertebral features. The sacrum consists of trabecular bone envel- a convexity. Four pairs of pelvic sacral foramina communicate with the
oped by a shell of compact bone of varying thickness. sacral canal through intervertebral foramina, and transmit ventral rami
of the upper four sacral spinal nerves. The large area between the right
BaseThe base (Fig. 43.48) is the upper surface of the first sacral ver- and left foramina, which is formed by the flat pelvic aspects of the sacral
tebra, the least modified from the typical vertebral plan. The body is bodies, bears evidence of their fusion at four transverse ridges. The
large and wider transversely, and its anterior projecting edge is the sacral longitudinal bars between the foramina are costal elements, which fuse


promontory. The vertebral foramen is triangular; its pedicles are short to the vertebrae. Lateral to the foramina, the costal elements unite.
and diverge posterolaterally. The laminae are oblique, inclining down Posteriorly, they unite with the transverse processes to form the lateral
posteromedially to meet at a spinous tubercle. The superior articular part of the sacrum, which expands basally as the ala.
processes project cranially, with concave articular facets directed pos- The first three sacral ventral rami emerge from the pelvic sacral
teromedially to articulate with the inferior articular processes of the fifth foramina and pass anterior to piriformis. The sympathetic trunks
lumbar vertebra. The posterior part of each process projects backwards descend in contact with bone, medial to the foramina, as do the median
and its lateral aspect bears a rough area homologous with a lumbar sacral vessels in the midline. Lateral to the foramina, lateral sacral
mammillary process. vessels are related to bone. Ventral surfaces of the first, second and part
The transverse process is much modified as a broad, sloping mass of the third sacral bodies are covered by parietal peritoneum and
that projects laterally from the body, pedicle and superior articular crossed obliquely, left of the midline, by the attachment of the sigmoid
process. It is formed by the fusion of the transverse process and the mesocolon. The rectum is in contact with the pelvic surfaces of the third
costal element to each other and to the rest of the vertebra, and forms to fifth sacral vertebrae and with the bifurcation of the superior rectal
the upper surface of the sacral lateral mass or ala. artery between the rectum and third sacral vertebra.
Terminal fibres of the anterior and posterior longitudinal ligaments
are attached to the ventral and dorsal surfaces of the first sacral body. DorsalsurfaceThe posterosuperior aspect of the dorsal surface bears
Its upper laminar borders receive the lowest pair of ligamenta flava. The a raised, interrupted, median sacral crest with four (sometimes three)
ala is smooth superiorly, concave medially and rough laterally, and spinous tubercles, which represent fused sacral spines (Fig. 43.50).


BACk
728
5
NOITCES
A 1
2
Pedicle
7
3
Transverse
8
process
9
Vertebral
canal
Inferior
articular
process
4
Superior articular Lamina
process and facet
Spinous process
Psoas major
5
6
Fig .43 .49 The sacrum, anterior (pelvic) surface . Key: 1, upper border
of body of S1 (sacral promontory); 2, superior articular process of S1;
3, attachment of iliacus; 4, attachment of piriformis; 5, attachment of
coccygeus; 6, coccyx; 7, ala; 8, incompletely fused S1–2 intervertebral
joint; 9, first pelvic sacral foramen .
1 10
11
2
3
B
4
Erector Right L4 Thecal sac Left L4/5 12
spinae nerve root facet joint
Fig .43 .47 Lumbar vertebrae . A, The fifth lumbar vertebra, superior 13
aspect . B, A high-resolution axial CT scan through the lumbar spine at 5
the level of the fourth lumbar vertebra .
6
1
7
8
6
2 9
Fig .43 .50 The sacrum, posterior (dorsal) surface . Key: 1, superior
3 articular facet of S1; 2, ala; 3, first dorsal sacral foramen; 4, attachments
of interosseous sacroiliac ligaments; 5, lateral crest and transverse
4
7 tubercles; 6, median crest and spinous processes; 7, attachment of
5
gluteus maximus; 8, sacral hiatus; 9, cornua; 10, intermediate crest and
Fig .43 .48 The sacrum, superior aspect (base) . Key: 1, body of S1; articular tubercle (inferior articular process); 11, posterior surface of body
2, posterosuperior ala (transverse process element); 3, superior articular of S1 forming anterior wall of sacral canal; 12, area of attachment of


process; 4, sacral canal; 5, spinous process of S1; 6, anterosuperior ala multifidus (bounded by thin line); 13, attachment of erector spinae
(costal element); 7, lamina . aponeurosis (thick line) .


Bones
729
34
RETPAHC
Below the fourth (or third) tubercle there is an arched sacral hiatus in half vertebral arch between the second and fifth years, and the con-
the posterior wall of the sacral canal. This hiatus is produced by the joined element so formed unites anteriorly with the centrum and pos-
failure of the laminae of the fifth sacral vertebra to meet in the median teriorly with its opposite fellow at about the eighth year. Thereafter, the
plane, and as a result the posterior surface of the body of that vertebra upper and lower surfaces of each sacral body are covered by an epiphy-
is exposed on the dorsal surface of the sacrum. Flanking the median sial plate of hyaline cartilage, which is separated from its neighbour by
crest, the posterior surface is formed by fused laminae, and lateral to the fibrocartilaginous precursor of an intervertebral disc. Laterally, suc-
this are four pairs of dorsal sacral foramina. Like the pelvic foramina, cessive conjoined vertebral arches and costal elements are separated by
they lead into the sacral canal through intervertebral foramina, and hyaline cartilage; a cartilaginous epiphysis, sometimes divided into
each transmits the dorsal ramus of a sacral spinal nerve. Medial to the upper and lower parts, develops on each auricular and adjacent lateral
foramina, and vertically below each articular process of the first sacral surface. Soon after puberty, the fused vertebral arches and costal ele-
vertebra, is a row of four small tubercles, which collectively constitute ments of adjacent vertebrae begin to coalesce from below upwards. At
the intermediate sacral crest. These are sometimes termed articular the same time, individual epiphysial centres develop for the upper and
tubercles, and represent fused contiguous articular processes. The infe- lower surfaces of bodies, spinous tubercles, transverse tubercles and
rior articular processes of the fifth sacral vertebra are free and project costal elements.
downwards at the sides of the sacral hiatus as sacral cornua, connected The costal epiphysial centres appear at the lateral extremities of the


to coccygeal cornua by intercornual ligaments. The interrupted rough- hyaline cartilages between adjacent costal elements; two anterior and
ened crest to the lateral side of the dorsal sacral foramina is the lateral two posterior centres appear in each of the intervals between the first,
sacral crest, which is formed by fused transverse processes, whose apices second and third sacral vertebrae. Ossification spreads from these into
appear as a row of transverse tubercles. the auricular epiphysial plates. One costal epiphysial centre, placed
The upper three sacral spinal dorsal rami pierce multifidus as they anteriorly, occurs in each remaining interval and from them ossification
emerge via dorsal foramina. spreads to the epiphysial plate covering the lower part of the lateral
surface of the sacrum. Sacral bodies unite at their adjacent margins after
LateralsurfaceThe lateral surface (Fig. 43.51A) is a fusion of trans- the twentieth year, but the central and greater part of each intervertebral
verse processes and costal elements. It is wide above and rapidly narrows disc remains unossified up to or beyond middle life.
in its lower part. The broad upper part bears an auricular surface for
articulation with the ilium, and the area posterior to this is rough and VariantsThe sacrum may contain six vertebrae, by development of an
deeply pitted by the attachment of ligaments. The auricular surface, additional sacral element or by incorporation of the fifth lumbar or first
borne by costal elements, is like an inverted letter L. The shorter, cranial coccygeal vertebra. Inclusion of the fifth lumbar vertebra (sacralization)
limb is restricted to the first sacral vertebra; the caudal limb descends is usually incomplete and limited to one side. In the most minor degree
to the middle of the third. Beyond this, the lateral surface is non- of the abnormality, a fifth lumbar transverse process is large and articu-
articular and reduced in breadth. Caudally, it curves medially to the lates, sometimes by a synovial joint, with the sacrum at the posterola-
body of the fifth sacral vertebra at the inferior lateral angle, beyond teral angle of its base. Reduction of sacral constituents is less common


which the surface becomes a thin lateral border. A variable accessory but lumbarization of the first sacral vertebra does occur; it remains
sacral articular facet sometimes occurs, posterior to the auricular surface. partially or completely separate. The bodies of the first two sacral ver-
The auricular surface is covered by hyaline cartilage, and formed tebrae may remain unfused when the lateral masses are fused. The
entirely by costal elements. It shows cranial and caudal elevations and dorsal wall of the sacral canal may be variably deficient, due to imper-
an intermediate depression, behind which a third elevation is visible in fect development of laminae and spines. Orientation of the superior
the elderly. The surface becomes more corrugated with age. The rough sacral articular facets displays wide variation, as does the sagittal curva-
area behind the auricular surface shows two or three marked depres- ture of the sacrum. Asymmetry (facet tropism) of the superior facets
sions for the attachment of strong interosseous sacroiliac ligaments. alters the relation between the planes of the two lumbosacral facet
Below the auricular surface the sacrotuberous and sacrospinous liga- joints.
ments are attached between gluteus maximus dorsally and coccygeus
ventrally. SexdifferencesinsacraSex differences in sacra are described on
page 1348.
ApexThe apex is the inferior aspect of the fifth sacral vertebral body,
and bears an oval facet for articulation with the coccyx.
COCCYX
SacralcanalThe sacral canal (Fig. 43.51B) is formed by sacral ver-
tebral foramina, and is triangular in section (see Fig. 43.48). Its upper The coccyx (Fig. 43.53) is a small, triangular bone and is often asym-
opening, seen on the basal surface, appears to be set obliquely. The metrical in shape. It usually consists of four fused rudimentary verte-
inclination of the sacrum means that it is directed cranially in the stand- brae, although the number varies from three to five, and the first is
ing position. Each lateral wall presents four intervertebral foramina, sometimes separate. The bone is directed downwards and ventrally