CHAPTER 37 ANATOMIC APPROACHES TO THE SPINE
1643
Trigeminal V1
nerve V2
V3
Musculocutan.
Medial cutan.
Post. cutan.
Dorsal cutan.
Lateral
Medial
Posterior
Superior clavicular
Occipitals
Anterior
cutan.
Saphenous
Lat. cutan.
Sup. peroneal
Deep peroneal
med.
lat.
T4 Axillary
Radial
Median
Ilio- Ulnar
Sural
Plantars
inguinal
Lat. cutan.
nerve of
thigh
Posterior
cutan.
C3
C2
C4
T3
T6
T8
T10
T12
C5
T2
T1
C6
C8
C7
L1
L2
L3
L4
L5
S1
S4
C7
C8
C6
T1
T2
C5
C4
C3
C2
T3
T4
T6
T8
T10
T12
S5
S3
S1
L4
L4
L3
L5
Tibial S1
Sciatic
Common peroneal
Femoral
Radial
Intercostals
Anterior Posterior
Dermatomes Dermatomes
Cutaneous
nerves
FIGURE 37.2 Dermatomal and sensory distribution. (Redrawn
from Patton HD, Sundsten JW, Crill WE, et al, editors: Introduction to
basic neurology , Philadelphia, 1976, WB Saunders.)
FIGURE 37.1 Vertebral column: upper cervical vertebrae
(occiput to C2), lower cervical vertebrae (C3-7), thoracic vertebrae
(T1-12), lumbar vertebrae (L1-5), sacrum, and coccyx.
cord are tracts of ascending (sensory) and descending (motor)
nerve £bers. ¢ese pathways typically are arranged with cervi-
cal tracts located centrally and thoracic, lumbar, and sacral tracts
located progressively peripheral. ¢is accounts for the clinical
£ndings of central cord syndrome and syrinx. Understanding
the location of these tracts aids in understanding di¦erent spinal
Spinal nerves exit the canal at each level. Spinal nerves
C2-7 exit above the pedicle for which they are named (the C6
nerve root exits the foramen between the C5 and C6 pedicles).
¢e C8 nerve root exits the foramen between the C7 and T1
pedicles. All spinal nerves caudal to C8 exit the foramen below
the pedicle for which they are named (the L4 nerve root exits
the foramen between the L4 and L5 pedicles). ¢e £nal der-
matomal and sensory nerve distributions are shown in Figure
37.2 . Because the spinal cord is shorter than the vertebral col-
umn, the spinal nerves course more vertically as one moves
caudally. Each level gives o¦ a dorsal (sensory) root and a ven-
tral (mostly motor) root, which combine to form the mixed
spinal nerve. ¢e dorsal root of each spinal nerve has a gan-
glion located near the exit zone of each foramen. ¢is dorsal
root ganglion is the synapse point for the ascending sensory
cell bodies. ¢is structure is sensitive to pressure and heat and
can cause a dysesthetic pain response if manipulated.
ANATOMY OF CERVICAL,
THORACIC, AND LUMBAR PEDICLES
Numerous studies have documented the anatomic morphol-
ogy of the cervical, thoracic, and lumbar vertebrae. Advanced
internal £xation techniques, including pedicle screws, have
been developed and used extensively in spine surgery, not
only for traumatic injuries but also for degenerative condi-
tions. As the role for anterior and posterior spinal instrumen-
tation continues to evolve, understanding the morphologic
characteristics of the human vertebrae is crucial in avoiding
complications during £xation.
Placement of screws in the cervical pedicles is controversial
and carries more risk than anterior plate or lateral mass £xa-
tion. Although cervical pedicles can be suitable for screw £xa-
tion, uniformly sized cervical pedicle screws cannot be used at
Motor Bidirectional
(descending paths
paths)
Sensory
(ascending
paths)
2
Anterior spinal
artery
Anterior motor
nerve root
Dentate
ligament
9
8
6
7
1
3
4 5
2.5-4 cm
Intermediolateral
grey nucleus
(sympathetic)
S = sacral
T = thoracic
C = cervical
S T C
S
T C
C TS
FIGURE 37.3 Schematic cross section of cervical spinal cord.
(Redrawn from Patton HD, Sundsten JW, Crill WE, et al, editors: Introduc-
tion to basic neurology , Philadelphia, 1976, WB Saunders.)
Occipital – C2
C3 – C7
T1–T12
L1– L5
Sacrum
and
coccyx