CHAPTER 37
ANATOMIC APPROACHES TO THE SPINE
Raymond J. Gardocki
ANATOMY OF VERTEBRAL
COLUMN 1642
ANATOMY OF SPINAL
JOINTS 1642
ANATOMY OF SPINAL
CORD AND NERVES 1642
ANATOMY OF CERVICAL,
THORACIC, AND
LUMBAR PEDICLES 1643
CIRCULATION OF SPINAL
CORD 1646
SURGICAL APPROACHES 1647
Anterior approaches 1647
Anterior approach, occiput to C3 1648
Extended maxillotomy and
subtotal maxillectomy 1649
Anterior approach, C3 to C7 1653
Anterolateral approach, C2 to C7 1654
Anterior approach to
cervicothoracic junction,
C7 to T1 1655
Anterior approach to the thoracic
spine 1661
Video-assisted thoracic surgery 1661
Anterior approach to the
thoracolumbar junction 1662
Anterior retroperitoneal
approach, L1 to L5 1664
Percutaneous lateral approach
to lumbar spine, L1 to L4-5
(Dlif Or Xlif) 1666
Anterior transperitoneal
approach to the lumbosacral
junction, L5 to S1 1668
Video-assisted lumbar surgery 1672
Posterior approaches 1673
Minimally Invasive Approaches
to the Posterior Spine 1675
1642
ANATOMY OF VERTEBRAL COLUMN
¢e vertebral column comprises 33 vertebrae divided into £ve
sections (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coc-
cygeal) ( Fig. 37.1 ). ¢e sacral and coccygeal vertebrae are fused,
which typically allows for 24 mobile segments. Congenital
anomalies and variations in segmentation are common. ¢e cer-
vical and lumbar segments develop lordosis as an erect posture
is acquired. ¢e thoracic and sacral segments maintain kyphotic
postures, which are found in utero, and serve as attachment
points for the rib cage and pelvic girdle. In general, each mobile
vertebral body increases in size when moving from cranial to
caudal. A typical vertebra comprises an anterior body and a pos-
terior arch that enclose the vertebral canal. ¢e neural arch is
composed of two pedicles laterally and two laminae posteriorly
that are united to form the spinous process. To either side of the
arch of the vertebral body is a transverse process and superior
and inferior articular processes. ¢e articular processes articu-
late with adjacent vertebrae to form synovial joints. ¢e relative
orientation of the articular processes accounts for the degree of
¡exion, extension, or rotation possible in each segment of the
vertebral column. ¢e spinous and transverse processes serve as
levers for the numerous muscles attached to them. ¢e length of
the vertebral column averages 72 cm in men and 7 to 10 cm less
in women. ¢e vertebral canal extends throughout the length of
the column and provides protection for the spinal cord, conus
medullaris, and cauda equina.
ANATOMY OF SPINAL JOINTS
¢e individual vertebrae are connected by joints between the
neural arches and between the bodies. ¢e joints between the
neural arches are the zygapophyseal joints or facet joints. ¢ey
exist between the inferior articular process of one vertebra and
the superior articular process of the vertebra immediately cau-
dal. ¢ese are synovial joints with surfaces covered by artic-
ular cartilage, a synovial membrane bridging the margins of
the articular cartilage, and a joint capsule enclosing them. ¢e
branches of the posterior primary rami innervate these joints.
¢e interbody joints contain specialized structures called
intervertebral discs. ¢ese discs are found throughout the ver-
tebral column except between the £rst and second cervical
vertebrae. ¢e discs are designed to accommodate move-
ment, weight bearing, and shock by being strong but deform-
able. Each disc contains a pair of vertebral endplates with a
central nucleus pulposus and a peripheral ring of annulus
£brosus sandwiched between them. ¢ey form a secondary
cartilaginous joint or symphysis at each vertebral level.
¢e vertebral endplates are 1-mm thick sheets of cartilage-
£brocartilage and hyaline cartilage with an increased ratio of
£brocartilage with increasing age. ¢e nucleus pulposus is a
semi¡uid mass of mucoid material, 70% to 90% water, with
proteoglycan constituting 65% and collagen constituting 15%
to 20% of the dry weight. ¢e annulus £brosus consists of 12
concentric lamellae, with alternating orientation of collagen
£bers in successive lamellae to withstand multidirectional
strain. ¢e annulus is 60% to 70% water, with collagen con-
stituting 50% to 60% and proteoglycan about 20% of the dry
weight. With age, the proportions of proteoglycan and water
decrease. ¢e annulus and nucleus merge in a junctional zone
without a strict demarcation. ¢e discs are the largest avas-
cular structures in the body and depend on di¦usion from a
specialized network of endplate blood vessels for nutrition.
ANATOMY OF SPINAL CORD AND
NERVES
¢e spinal cord is shorter than the vertebral column and termi-
nates as the conus medullaris at the second lumbar vertebra in
adultsandthethirdlumbarvertebrainneonates.Fromtheconus,
a £brous cord called the "lum terminale extends to the dorsum of
the £rst coccygeal segment. ¢e spinal cord is enclosed in three
protective membranes—the pia, arachnoid, and dura mater. ¢e
pia and arachnoid membranes are separated by the subarachnoid
space, which contains the cerebrospinal ¡uid. ¢e spinal cord has
enlargements in the cervical and lumbar regions that correlate
with the brachial plexus and lumbar plexus. Within the spinal