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The second edition of Synopsis of Spine Surgery reflects the rapid advances in
the field since the first edition, advances that have changed our approach to
patient care. These advances, in diagnostic imaging, spinal instrumentation,
and osteobiologics, have emerged at a staggering pace inundating the prac-
ticing spine surgeon, orthopedic/neurosurgery resident, and nonoperative
spine physician with an enormous amount of new information to digest and
comprehend. The premise behind this book is to succinctly summarize such
information in an outline format. The reader is able to peruse broad topics in
an expeditious manner while being directed to key references that may
provide greater detail on the topics of particular interest.
Synopsis of Spine Surgery takes account of current developments in spine
surgery and reflects the many years of clinical and surgical experience of the
senior author. This book is written primarily for orthopedic surgeons and neuro-
surgeons-in-training. The easy-to-read format, however, makes this an excellent
resource for practicing spine surgeons as well as nonoperative spine physicians.
We hope that this book will provide our readers with a thorough understanding
of the modern field of spine surgery in the most efficacious manner possible,
increasing the quality of care given to spine patients.
Preface
I
Patient Evaluation
and Spine Overview
1 Anatomy and Surgical Approaches
2 History and Physical Examination
3 Spinal Imaging and Diagnostic Tests
4 Biomechanics of the Spine and Spinal Instrumentation
5 Physiology of Bone Grafts and Bone
Graft Substitutes
1
Anatomy and Surgical
Approaches
Basic Anatomy of the Spine
I. Vertebral Column
A. The spinal column has specifically adapted anatomic features to main-
tain stability, protect neural elements, and allow range of motion.
B. Stability is augmented by the intervertebral disks, ligaments, and muscles.
C. There are 33 vertebrae in the spinal column (seven cervical, 12 thoracic,
five lumbar, five sacral, and four coccygeal).
D. There are four sagittal curves in the vertebral column.
1. Cervical lordosis
2. Thoracic kyphosis
3. Lumbar lordosis
4. Sacral kyphosis
E. The kyphotic curves are called primary because they form during the fetal
period.
1. Caused by the wedge-shaped nature of vertebrae
F. The lordotic curves are called secondary because they begin to form dur-
ing the late fetal period and continue to form after birth. Head and body
weight contributes to their formation.
1. Caused by differences in the anteroposterior (AP) dimensions of the
intervertebral disks.
G. Each vertebra consists of a posterior bony arch and an anterior body, both
of which surround the vertebral canal. Posterior bony arches between two
adjacent vertebrae form a foramen for the spinal nerve roots. Anterior bod-
ies of the lumbar spine support 80% of the axial load on the spinal column.
H. Posterior bony arch components
1. Pedicles and laminae
a. Form the borders of vertebral canal with the posterior border of the
vertebral body
3
◆
4 I Patient Evaluation and Spine Overview
2. Spinous and transverse processes
a. Attachment sites for supporting ligaments and muscles
3. Articular processes
a. Pars interarticularis is the bony region between superior and infe-
rior articular process an individual vertebra.
b. Facet joints between articular processes of adjacent vertebrae
support 20% of axial load on the spinal column.
II. Intervertebral disks
A. Located between vertebral end plates, which are covered by hyaline
cartilage and supported by subchondral bone
B. The inside of the disk contains the nucleus pulposus, which cushions the
axial load. This nucleus is made of mucoid type II collagen.
C. The disk is a relatively avascular structure with the outer layers receiving
nutrients from the end arterioles and the central portions receiving
nutrients by diffusion from vertebral end plates
D. Anulus fibrosus
1. Outer portion of the disk
2. Made of type I collagen
3. Lattice made of sheets running in opposite direction that give the disk
greater rotational strength
4. Thickest portion is anterior. Thinnest is posterolateral.
5. Outer portions of anulus are continuous with the anterior and
posterior longitudinal ligaments.
E. Vertebral disks make up one quarter of the spinal column height. The disks
expand when the column is horizontal because water and nutrients enter
the disk, but they collapse under the stress of prolonged standing.
Neuroanatomy
I. Spinal cord
A. Gross structure
1. Spinal cord ends at L1–L2 (conus medullaris)
a. It may be as high as T12 or as low as L2–L3
b. In newborn infants, the cord ends at L2–L3
2. Length: 45-cm cord and 25-cm filium terminale (10% increase in
length with flexion, mostly at C1, T1, and L1, least at C6 and T6)
3. Mean diameter (10 mm, frontal larger than sagittal)
4. Relationship between cord and vertebral segments (Fig. 1–1)
(Table 1–1)
B. Internal structures (Fig. 1–2)
1. The peripheral white matter and central gray matter
a. Gray matter: cell bodies of efferent neurons
(1) Posterior horns: somatosensory
(2) Anterior horns: somatomotory
(3) Intermediolateral horns: visceral
(4) Reflex somatic centers
◆
Chapter 1 Anatomy and Surgical Approaches 5
Figure 1–1 Diagram of the spinal cord and nerve roots.
The spinal cord emerges from the foramen magnum as a
continuation of the medulla oblongata and ends in a cone-
shaped structure known as the conus medullaris. The
location of the conus medullaris is usually the L1–L2 inter-
vertebral disk in adults. The cervical cord enlarges maxi-
mally at C6 vertebra to provide C3–T2 innervation to the
upper limbs, and the lumbosacral enlargement is present
at T11 to L1 vertebral segments to provide L1 to S3 cord
segments to the lower extremities. (From An HS. Principles
and Techniques of Spine Surgery. Baltimore: Williams and
Wilkins; 1998. Reprinted with permission.)
Table 1–1 Relationship between Cord
and Vertebral Segments
Cord Segment Vertebral Segment
C1 C1
C8 C7
T6 T5
T12 T8
L2 T10
L5 T11
S3 T12
6 I Patient Evaluation and Spine Overview
Figure 1–2 Cross section of the spinal cord with the outer white matter and the inner gray matter.
The white matter of the spinal cord contains nerve fibers and glia and is divided into three columns:
posterior, lateral, and anterior. The posterior column includes the fasciculus cuneatus laterally and fas-
ciculus gracilis medially. The lateral column contains the descending motor lateral corticospinal and
lateral spinothalamic fasciculi, and the anterior funiculus contains the ascending anterior spinothala-
mic tract and other descending tracts. The lateral spinothalamic tracts cross through the ventral com-
missure to the contralateral side of the cord. The gray matter of the spinal cord contains cell bodies of
efferent and internuncial neurons.
b. White matter: nerve fibers and glia
(1) Posterior funiculus: posterior columns (fasciculus cuneatus
laterally and gracilis medially)
(2) Lateral funiculus: lateral corticospinal and lateral spinothalamic
fasciculus
(3) Anterior funiculus: anterior spinothalamic tract
2. Central ependymal canal: passage of cerebrospinal fluid
Chapter 1 Anatomy and Surgical Approaches 7
C. Spinal cord function
1. Motor function: cerebral cortex, internal capsule, corticospinal tract,
pyramidal tract (90% decussate at the medulla to the contralateral
lateral corticospinal fasciculus), anterior horn cells
a. Lateral corticospinal fasciculus: tracts for the upper extremities are
medial to the lower extremities
b. Central cord syndrome: spares the most lateral tracts in the lateral
corticospinal fasciculus (upper extremity motor function) and
retains the medial tracts (lower extremity motor function)
2. Sensory function
a. Posterior columns: tactile discrimination, proprioception, and vibration
sense (stereognosis, two-point discrimination)
(1) Fasciculus gracilis: lower limbs and above midthorax
(2) Fasciculus cuneatus: upper limbs and below midthorax
(3) Sensory tracts cross to the opposite side in the medulla
oblongata and to the sensory cortex
(4) Anterior cord syndrome: only posterior column functions are
spared.
b. Lateral spinothalamic fasciculus: pain, temperature, and light touch
(1) Most fibers cross through the ventral commissure to the opposite
side and ascend through the lateral spinothalamic tract.
(2) Brown-Sequard syndrome: pain and temperature loss is
contralateral, whereas motor and proprioception loss are
ipsilateral.
c. Anterior spinothalamic fasciculus
(1) Crude touch
(2) Posterior cord syndrome: only crude touch is spared
D. Vascularity of the spinal cord
1. Cervical spine
a. The anterior spinal artery: the major vessel for anterior and central
aspects of the cord
(1) Two medullary feeders at the brain stem by the vertebral
arteries
(2) Other medullary feeders from the vertebral arteries and
ascending cervical arteries, particularly C2 and C6 from the left
and C2, C5, C6 from the right
b. Two posterior spinal arteries from the posterior inferior cerebellar
arteries have minimal contribution to the central gray matter.
2. Thoracolumbar spine
a. The anterior spinal artery, two posterior spinal arteries
b. Feeders
(1) Superior intercostal artery: branch of deep cervical artery,
which is a branch of the right subclavian artery, feeds the cord
at the cervical-thoracic junction.
(2) One to five segmental vessels: tenuous blood supply for
the upper thoracic cord (watershed critical zone from T4
to T10)