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Chapter 17 Discography 313
psychological factors, chronic pain behavior, regional or central
pain syndromes, and compensation issues.
3.
Provocative discography has not been proven to improve
outcomes of treatment for low back pain syndromes. In patients
with emotional distress issues or compensation issues, there is
some evidence that using discography may result in poorer
outcomes and inappropriate invasive procedures.
4.
Risks of provocative discography include false and misleading
diagnoses in patients with high pain-sensitive risk factors, increased
axial pain for weeks or months after injection, pyogenic discitis,
and accelerated disc degeneration after long-term follow-up.
KEY REFERENCES
1. Sackett D, Haynes R. Evidence base of clinical diagnosis: the
architecture of diagnostic research. BMJ. 2002;324:539-541.
This article denes the necessary conditions to establish validity and
clinical usefulness of a diagnostic test. The gold standard necessary
to compare diagnostic test results is of prime importance, as is a
careful assessment of the study population. These conditions are
problematic in the evaluation of provocative discography.
2.
Carragee EJ, Tanner CM, Yang B, et al. False-positive ndings on
lumbar discography: reliability of subjective concordance
assessment during provocative disc injection. Spine.
1999;24:2542-2547.
This study looks at the reliability of the concordance response during
discography. The authors found that volunteer subjects with known
pelvic area pain cannot reliably distinguish the sensation coming
from a pelvic pain generator from the sensation caused by the
injection of an asymptomatic disc. The implications for validity of
provocative injections are discussed.
3.
Ohtori S, Kinoshita T, Yamashita M, et al. Results of surgery for
discogenic low back pain: a randomized study using discography
versus discoblock for diagnosis. Spine. 2009;34:1345-1348.
The authors performed a randomized clinical trial comparing
outcomes of subjects having single-level fusion based on an
evaluation using provocative discography with subjects having
an anesthetic disc injection. These were in some respects best-case
scenario subjects (no psychological distress, no depression, no
worker’s compensation cases, and no trac accident litigants).
The discography was performed using low-pressure injections.
The outcomes in the discography group (reported pain, function,
pain medications) were uniformly worse than the group using an
anesthetic block to determine fusion.
4.
Carragee EJ, Don AS, Hurwitz EJ, et al. Does discography cause
accelerated progression of degeneration changes in the lumbar
disc: a ten-year matched cohort study. Spine. 2009;34:2338-2345.
Matched asymptomatic cohorts with and without baseline
pressure-limited provocative discography were followed with a
detailed MRI protocol compared against baseline MRI ndings. The
discography group had greater progression of disc degeneration
scores, more new disc herniations, greater loss of disc height, and
greater loss of disc signal compared with the control group. In the
discography cohort, new disc herniations were disproportionately
found near the puncture site.
5.
Chou R, Loesser JD, Owens DK. Interventional therapies, surgery,
and interdisciplinary rehabilitation for low back pain: an
evidence-based clinical practice guideline from the American
Pain Society. Spine. 2009;34:1066-1077.
In a comprehensive multidisciplinary review, the authors
concluded: “In patients with chronic nonradicular low back pain,
provocative discography is not recommended as a procedure for
diagnosing discogenic low back pain (strong recommendation,
moderate-quality evidence).”
REFERENCES
1. Lindblom L. Diagnostic puncture of intervertebral disks in
sciatica. Acta Orthop Scand. 1948;17:231-239.
2. Derby R, Guyer R, Lee S-H, et al. e rational use and
limitations of provocative discography. International Spine
Intervention Society 13th annual meeting, New York. ISIS
Newsletter. 2004;5:6-20.
3. Walsh T, Weinstein J, Spratt K, et al. Lumbar discography in
normal subjects: a controlled prospective study. J Bone Joint
Surg Am. 1990;72:1081-1088.
4. Allan DB, Waddell G. An historical perspective on low back
pain and disability. Acta Orthop Scand Suppl. 1989;234:1-23.
5. Burton A. Spine update: back injury and work loss: biomechanical
and psychosocial inuences. Spine. 1997;22:2575-2580.
6. Burton A, Tillotson K, Main C, et al. Psychosocial predictors
of outcome in acute and subacute low back trouble. Spine.
1995;20:722-728.
7. Aprill C, Bogduk N. High-intensity zone: a diagnostic sign
of painful lumbar disc on magnetic resonance imaging. Br J
Radiol. 1992;65:361-369.
8. Crock H. Internal disc disruption. Med J Aust. 1970;1:983-990.
9. Derby R, Howard MW, Grant JM, et al. e ability of
pressure-controlled discography to predict surgical and
nonsurgical outcomes. Spine. 1999;24:364-371.
10. O’Neill C, Derby R, Kanderes L. Precision injection techniques
for diagnosis and treatment of lumbar disc disease. Semin Spine
Surg. 1999;11:104-118.
11. Schwarzer A, Aprill C, Derby R, et al. e prevalence and
clinical features of internal disc disruption in patients with
chronic LBP. Spine. 1995;20:1878-1883.
12. Schwarzer A, Aprill C, Fortin J, et al. e relative contribution
of the zygapophyseal joint in chronic low back pain. Spine.
1994;19:801-806.
13. Schwarzer A, Bogduk N. e prevalence and clinical features of
internal disk disruption in patients with low back pain [letter].
Spine. 1996;21:776.
14. Siddle P, Cousins M. Spinal pain mechanisms. Spine. 1997;22:
98-104.
15. Carragee EJ, Tanner CM, Yang B, et al. False-positive ndings
on lumbar discography: reliability of subjective concordance
assessment during provocative disc injection. Spine.
1999;24:2542-2547.
16. Carragee EJ, Tanner CM, Khurana S, et al. e rates of
false-positive lumbar discography in select patients without low
back symptoms. Spine. 2000;25:1373-1380.
17. Gracely R, Dubner R, McGrath P. Narcotic analgesia: fentanyl
reduces the intensity but not the unpleasantness of painful
tooth pulp stimulation. Science. 1979;203:1261-1263.
18. Lenz F, Gracely R, Romanoski A, et al. Stimulation in the
somatosensory thalamus can reproduce both the aective and
sensory dimensions of previously experienced pain. Nat Med.
1995;1:910-913.
19. Lenz FA, Gracely RH, Hope EJ, et al. e sensation of angina
can be evoked by stimulation of the human thalamus. Pain.
1994;59:119-125.
20. Saal JSM. General principles of diagnostic testing as related to
painful lumbar spine disorders—a critical appraisal of current
diagnostic techniques. Spine. 2002;27:2538-2545.
21. Carragee EJ. Psychological screening in the surgical treatment
of lumbar disc herniation. Clin J Pain. 2001;17:215-219.
22. North R, Kidd D, Zahurak M, et al. Specicity of diagnostic
nerve blocks: a prospective, randomized study of sciatica due
to lumbosacral spine disease. Pain. 1996;65:77-85.
SECTION
II
314 DIAGNOSIS
23. O’Neill C, Kurgansky M. Subgroups of positive discs on
discography. Spine. 2004;29:2134-2139.
24. Handwerker HO, Kobal G. Psychophysiology of experimentally
induced pain. Physiol Rev. 1993;73:639-671.
25. Rhudy JL, Meagher MW. Fear and anxiety: divergent eects on
human pain thresholds. Pain. 2000;84:65-75.
26. Carragee E, Tanner C, Vittum D, et al. Positive provocative
discography as a misleading nding in the evaluation of low back
pain. Proceedings of the North American Spine Society, 1997,
p 388.
27. Sackett D, Haynes R. Evidence base of clinical diagnosis: the
architecture of diagnostic research. BMJ. 2002;324:539-541.
28. Schwarzer A, Wang S, Bogduk N, et al. Prevalence and clinical
features of lumbar zygapophysial joint pain: a study in an
Australian population with chronic low back pain. Ann Rheum
Dis. 1995;54:100-106.
29. Schwarzer AC, Aprill CN, Derby R, et al. e false-positive rate
of uncontrolled diagnostic blocks of the lumbar zygapophysial
joints. Pain. 1994;58:195-200.
30. Block A, Vanharanta H, Ohnmeiss D, et al. Discographic pain
report: inuence of psychological factors. Spine. 1996;21:
334-338.
31. Ohnmeiss DD, Vanharanta H, Guyer RD. e association
between pain drawings and computed tomographic/
discographic pain responses. Spine. 1995;20:729-733.
32. Schellhas KP, Pollei SR, Dorwart RH. oracic discography: a
safe and reliable technique. Spine. 1994;19:2103-2109.
33. Nordin M, Carragee EJ, Hogg-Johnson S, et al. Assessment
of neck pain and its associated disorders. Results of the Bone
and Joint Decade 2000-2010 Task Force on Neck Pain and Its
Associated Disorders. Spine. 2008;33:S101-S122.
34. Heggeness MH, Watters WC III, Gray PM Jr. Discography of
lumbar discs aer surgical treatment for disc herniation. Spine.
1997;22:1606-1609.
35. Carragee EJ, Chen Y, Tanner CM, et al. Provocative
discography in patients aer limited lumbar discectomy: a
controlled, randomized study of pain response in symptomatic
and asymptomatic subjects. Spine. 2000;25:3065-3071.
36. Derby R, Kim B-J, Lee S-H, et al. Comparison of discographic
ndings in asymptomatic subject discs and the negative
discs of chronic LBP patients: can discography distinguish
asymptomatic discs among morphologically abnormal discs?
Spine J. 2005;5:389-394.
37. Carragee EJ, Alamin TF, Miller J, et al. Provocative discography
in volunteer subjects with mild persistent low back pain. Spine
J. 2002;2:25-34.
38. Carragee EJ, Alamin TF, Parmar V, et al. Low pressure positive
discography in subjects asymptomatic of signicant LBP
illness. Spine. 2006;31:505-509.
39. Cohen SP, Hurley RW. e ability of diagnostic spinal injections
to predict surgical outcomes. Anesth Analg. 2007;105:1756-1775.
40. Colhoun E, McCall IW, Williams L, et al. Provocation
discography as a guide to planning operations on the spine.
J Bone Joint Surg Br. 1988;70:267-271.
41. Madan S, Gundanna M, Harley JM, et al. Does provocative
discography screening of discogenic back pain improve surgical
outcome? J Spinal Disord Tech. 2002;15:245-251.
42. Ohtori S, Kinoshita T, Yamashita M, et al. Results of surgery
for discogenic low back pain: a randomized study using
discography versus discoblock for diagnosis. Spine. 2009;34:
1345-1348.
43. Carragee EJ, Lincoln T, Parmar VS, et al. A gold standard
evaluation of the “discogenic pain” diagnosis as determined by
provocative discography. Spine. 2006;31:2115-2123.
44. Freeman BJ, Fraser RD, Cain CM, et al. A randomized,
double-blind, controlled trial: intradiscal electrothermal
therapy versus placebo for the treatment of chronic discogenic
low back pain. Spine. 2005;30:2369-2377.
45. Pauza KJ, Howell S, Dreyfuss P, et al. A randomized, placebo-
controlled trial of intradiscal electrothermal therapy for the
treatment of discogenic low back pain. Spine. 2004;4:27-35.
46. Derby R, Lettice JJ, Kula TA, et al. Single-level lumbar fusion in
chronic discogenic low-back pain: psychological and emotional
status as a predictor of outcome measured using the 36-item
Short Form. J Neurosurg Spine. 2005;3:255-261.
47. Carragee EJ, Chen Y, Tanner CM, et al. Can discography
cause long-term back symptoms in previously asymptomatic
subjects? Spine. 2000;25:1803-1808.
48. Korecki CL, Costi JJ, Iatridis JC. Needle puncture injury aects
intervertebral disc mechanics and biology in an organ culture
model. Spine. 2008;33:235-241.
49. Nassr A, Lee JY, Bashir RS, et al. Does incorrect level needle
localization during anterior cervical discectomy and fusion
lead to accelerated disc degeneration? Spine. 2009;34:189-192.
50. Carragee EJ, Don AS, Hurwitz EL, et al. Does discography
cause accelerated progression of degeneration changes in the
lumbar disc: a ten-year matched cohort study. Spine. 2009;34:
2338-2345.
51. Cuellar JM, Stau MP, Herzog RJ, et al. Does provocative
discography cause clinically important injury to the lumbar
intervertebral disc? A 10-year matched cohort study. Spine J.
2016;16(3):273-280.
III
SECTION
SURGICAL ANATOMY AND APPROACHES
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SECTION
18
Cervical Spine: Surgical Approaches
CHAPTER
e cervical spine is a complex structure with many sensitive
anatomic elements. Successful surgical manipulation of the
cervical spine requires an in-depth understanding of how
vascular, neural, and musculoskeletal elements interweave in
order to prevent dire complications. is chapter rst exam-
ines the anatomy of the cervical spine, focusing on surface
anatomy, osseous anatomy, bony articulations, ligaments,
intervertebral discs, neurovascular structures, musculature,
and triangles of the cervical spine. In the second section, the
applied surgical anatomy is explored, with descriptions of
both anterior and posterior approaches to the cervical spine.
Surgical Anatomy
Surface Anatomy and Skin
Surface landmarks are the key to successful localization of
specic vertebral levels. For example, prominent musculoskeletal structures—namely, the hyoid bone, thyroid cartilage, and
cricoid cartilage—delineate C3, C4, and C6, respectively.1 e
transverse processes can generally be palpated, with the transverse process of the atlas prominently featured anterior and
inferior to the mastoid process. e Chassaignac tubercle, the
anterior prominence of the transverse process of C6, is another
important landmark that can be palpated. When palpating in
a cranial-to-caudal direction along the posterior midline, the
spinous process of the second vertebra is the rst bony promi-
nence that can be felt. Due to the natural lordosis of the cervical spine, the next palpable spinous process is typically of the
sixth or seventh vertebra, with the seventh vertebra being
particularly prominent.
When considering anterior approaches, surgical incisions
should fall in line with skin creases to facilitate healing and
prevent more noticeable scarring. In the lower neck, skin
creases are transverse. Moving cranially, skin creases become
more oblique in orientation. Skin on the front of the neck is
generally soer, more mobile, and well vascularized, in con-
trast to skin on the back of the neck. As such, the typical
longitudinal midline skin incision used on the posterior neck
results in increased scar formation because of trapezius muscle
tension.
Hamid Hassanzadeh
Varun Puvanesarajah
Howard S. An
Osseous Anatomy and Bony Articulation
e cervical spine comprises the rst seven vertebrae in the
spinal column. e bony anatomy and articulations of the
upper cervical spine (occiput–C1–C2) are unique and distinct
from the remaining lower ve cervical vertebrae (C3–C7).
e atlas, or C1, is a ringlike structure lacking a body
and a spinous process. It consists of two thick lateral masses
plus an anterior and posterior arch. e longus colli muscle
and anterior longitudinal ligament attach to the anterior
tubercle of the atlas, whereas the posterior tubercle serves as
the bony attachments for the rectus minor muscle and suboccipital membrane. e superior and inferior oblique muscles
attach to the large transverse processes. e vertebral artery
passes through the foramen transversarium located within
the transverse process and courses posteriorly within a sulcus
on the superior aspect of the posterior arch of the atlas. In
15% of the population, the sulcus for the vertebral artery can
be completely covered by an anomalous ossication, which
has been called the ponticulus posticus and may have surgical
implications when identifying anatomic landmarks for bony
xation of C1.
e axis, or C2, is characterized by an odontoid process,
or dens, that projects upward anteriorly, articulating with the
posterior aspect of the anterior arch of the atlas as a synovial
joint. At its narrowest portion, at the base of the dens, the
coronal and sagittal plane diameters are 8 to 10 mm and 10
to 11 mm.
bid spinous process, which serve as attachments for the
rectus major and inferior oblique muscles. e zone between
the lamina and the lateral mass of the axis is indistinct, and
posteriorly the neural arch connects to the body by large
pedicles that are 8 mm wide and 10 mm long.5 Lying directly
anterolateral to the pedicle is the vertebral artery, which runs
through the foramen transversarium. e pedicle of the axis
projects 30 degrees medially and 20 degrees superiorly from
a posterior-to-anterior direction.
e bony articulations of the upper cervical spine (occiput–
C1–C2) are unique and warrant special attention (Fig. 18.1).
e atlanto-occipital articulation is a shallow ball-and-socket
joint allowing for considerable motion mostly in exion,
extension, and lateral bending. e greatest degree of exion
2
3,4
Posteriorly, the axis has a large lamina and a
4
III
317
318 SURGICAL ANATOMY AND APPROACHES
O
A
FIG. 18.1 Coronal cryomicrotome section of the upper cervical spine. Note
articulation between occiput (O) and atlas (A). The atlantoaxial joint is
identied by the arrow.
and extension of any cervical articulation occurs at this level
(25 degrees).6 Lateral displacement is minimized because the
lateral wall of the cup-shaped articulation of the atlas is higher
than the medial wall. e superior articular surface of the atlas
projects cephalad and medially, articulating with the occipital
condyle, which projects caudad and laterally. Conversely, the
inferior articular surface of the atlas projects caudad and
medially and articulates with the laterally projecting superior
facet of the axis. As a result of this bony conguration, axial
loads on the atlas tend to result in horizontal displacement of
the lateral masses.
7
e atlantoaxial articulation provides about 50% of rota-
tory motion of the cervical spine.
6,8
e transverse ligament,
which spans across the arch of the atlas, holds the odontoid
process against the anterior arch of the atlas, creating a pivot
joint with a synovial membrane and capsular ligaments anteriorly and posteriorly to the dens. is transverse ligament is
the principal stabilizing structure for the atlantoaxial articulation and averages 21.9 mm in length.9 e transverse ligament
has superior and inferior extensions, which form the cruciform
ligament of the atlas, connecting it to the anterior edge of the
foramen magnum and posterior aspect of the C2 body. To
allow more rotatory motion, the inferior facets of the atlas are
atter and more circular than the superior facets, and face
inferiorly to articulate with the axis.
e lower cervical vertebrae are morphologically similar
and increase in dimension as they proceed inferiorly from
C3 to C6, with C7 as the transitional vertebra into the thoracic spine. e vertebral bodies are small and oval, with
the mediolateral diameter greater than the anteroposterior
diameter.
e inferior surface of the vertebral body is convex in
the coronal plane and concave in the sagittal plane, with the
anterior lip occasionally overlapping the inferior vertebra.9
Conversely, the superior surface of the vertebral body is convex
or straight in the sagittal plane and concave in the coronal
plane, creating projections on either side of the lateral superior
surface, called the uncus, or hook. ese processes project
upward and conform to small grooves in the inferolateral
border of the cephalad vertebra, forming the uncovertebral
joints, or joints of Luschka. e width and depth of the vertebral surfaces average 17 mm and 15 mm from C2 to C6 and
increase to about 20 mm and 17 mm at C7. Vertebral heights
on the posterior wall in the mid-sagittal plane range from 11
to 13 mm.
10
e pedicles project posterolaterally from the vertebral
body and join the lamina to form the vertebral arch. From C3
to C7, the angulation of the pedicles varies from 8 degrees
below to 11 degrees above the transverse plane, and decreases
from 45 degrees to 30 degrees in relation to the sagittal plane.10
e width and height of the pedicles increase slightly in size
from C3 to C7, and average diameters are 5 to 6 mm and
7 mm. e lateral wall of the pedicle is thinner than the medial
wall and should be taken into consideration if attempts at
pedicle xation are considered in this region.
11–13
At the junction of the pedicle and lamina, the anterior
tubercle of the transverse process projects laterally and is connected to the posterior tubercle by the costotransverse lamella
(bar), creating the foramen transversarium. Passing through
the foramen transversarium is the vertebral artery and venous
system.
In the lower cervical spine, the neural foramina are bounded
anteriorly by the uncinate process, the posterolateral aspect of
the intervertebral disc, and the inferior portion of the vertebral
body; posteriorly by the facet joint and superior articular
process of the vertebral body below; and superiorly and
inferiorly by adjacent pedicles. Vertebral notches located on
the superior and inferior aspect of each pedicle contribute to
the size of the neural foramina, which are 9 to 12 mm in
height, 4 to 6 mm in width, and 4 to 6 mm in length, and are
aligned 45 degrees to the sagittal plane.
14,15
ey can be visual-
ized radiographically with oblique views, with the right neural
foramina outlined on the le posterior oblique view and the
le neural foramina outlined on the right posterior oblique
view.
e spinal canal is triangular and at all levels in the cervical
spine is signicantly greater in the medial-to-lateral dimen-
sion than in the anterior-to-posterior dimension. e crosssectional area of the spinal canal is largest at C2 and smallest
at C7, with a sagittal diameter of about 23 mm at C1 and
20 mm at C2, decreasing to 17 to 18 mm at C3–C6 and to
15 mm at C7.8 is is one reason that the passage of sublaminar wires is safer in the upper cervical spine than in the lower
cervical spine.
e lateral mass, an important structure for posterior
cervical plate-screw systems, forms at the junction of the
lamina and the pedicle and gives rise to the superior and
inferior articular processes. ese processes project upward
and downward and are angled approximately 45 degrees
cephalad from the transverse plane, gradually assuming a
more vertical position as they descend into the thoracic region
(Fig. 18.2). e articular process of the superior facet faces
posteriorly, whereas the inferior facet of the upper vertebra
faces anteriorly; the facets oppose one another to form a
zygapophyseal joint. e facet joints are true diarthrodial
Chapter 18 Cervical Spine: Surgical Approaches 319
O
T
SECTION
C5
C6
C7
FIG. 18.2 Parasagittal cryomicrotome section of facet joints. The lateral
mass of C7 is more elongated from superior to inferior and thinner from
anterior to posterior. The facet joint angle is roughly 45 degrees from the
transverse plane and assumes a more vertical position distally.
joints, with articular cartilage and menisci surrounded by a
brous capsule lined by a synovial membrane. e interfacet
distances are relatively constant between levels, with individual
variations ranging from 9 to 16 mm (average, 13 mm).
5,16
Posteriorly, the spinous processes project inferiorly and are
bid from C3 to C6; the C7 spinous process is large and not
bid, and is oen called the vertebra prominens. e junction
between the spinous process and lamina, the spinolaminar
line, is an important anatomic landmark during spinous
process wiring. Inadvertent penetration of the wire anterior to
this line may result in spinal cord impingement.
e cervicothoracic junction is a transition region, with C7
having similar anatomic characteristics as T1 and T2. e
dimensions of the vertebral body and the sizes of the transverse processes and spinous processes are larger at C6 and C7.
Additionally, dimensions of the spinal canal decrease at C6
and C7, representing a distinct transition to the thoracic
region. e articulating facet joint between C7 and T1
resembles the thoracic facet joint, and the lateral mass of C7
is thinner than that of upper levels. Morphologic characteristics of pedicles of C7, T1, and T2 were obtained with respect
to diameters, depths, and medial angulations. Inner diameters
of the pedicles at C7, T1, and T2 from medial to lateral plane
averaged 5.2, 6.3, and 5.5 mm. Medial angulations were 34, 30,
and 26 degrees at C7, T1, and T2, respectively.
10,17
ese
morphologic characteristics should be remembered when
performing transpedicular procedures in the cervicothoracic
region.
S
FIG. 18.3 Midsagittal microtome section at the upper cervical spine. The
transverse ligament (T ) acts as a stabilizer of the atlantoaxial joint by
helping to restrain the odontoid (O) from posterior translation. The spinal
cord (S), ligamentum avum (L), and posterior arch of atlas (A) are also
identied.
A
L
Ligaments
In addition to the bony anatomy, the ligamentous attachments
provide support to the cervical spine and associated articulations. In the atlanto-occipital complex, two membranous
attachments, the anterior and posterior atlanto-occipital
membranes, connect the anterior and posterior arch of C1 to
the margins of the foramen magnum. e anterior atlanto-
occipital membrane is the superior continuation of the anterior
longitudinal ligament, whereas the posterior membrane is the
superior continuation of the ligamentum avum.
e transverse ligament is the major stabilizer of the atlantoaxial complex (Fig. 18.3). It attaches laterally to tubercles
located on the posterior aspect of the anterior arch of C1,
where it blends with the lateral mass. Secondary stabilizers
include the thick alar ligament, which arises from the sides of
the dens to the medial aspects of the condyles of the occipital
bone, and the apical ligament, which arises from the apex of
the dens to the anterior edge of the foramen magnum. In some
individuals, an anterior atlantodental ligament exists connecting the base of the dens to the anterior arch of the atlas.18 e
tectorial membrane, the superior continuation of the posterior
longitudinal ligament, covers the dens and all the occipitoaxial
ligaments and extends from the posterior body of C2 to the
basilar portion of the occipital bone and the anterior aspect of
the foramen magnum.
e bodies of the lower cervical vertebrae (C3–C7) are
connected by two longitudinal ligaments and the intervertebral discs. e anterior longitudinal ligament is a strong band
that attaches from the skull, as the anterior atlanto-occipital
membrane, and continues caudad over the entire length of the
spine down to the sacrum. e anterior longitudinal ligament
is thinner and more closely attached at the intervertebral disc
margins than at the anterior vertebral surfaces.19 e anterior
longitudinal ligament also sweeps around and envelops the
lateral aspect of the vertebral bodies under the longus colli
III
320 SURGICAL ANATOMY AND APPROACHES
muscle, and the lateral extension is continuous with the deep
layer of the posterior longitudinal ligament in the region of
the intervertebral foramina.
e posterior longitudinal ligament, lying within the vertebral canal on the posterior aspect of the vertebral body and
intervertebral disc, is wider in the upper cervical spine than
the lower cervical spine.19 Superiorly, it is continuous with the
tectorial membrane; as it descends, it widens over the intervertebral discs and narrows behind each vertebral body. e
posterior longitudinal ligament supplies additional strength
and stability to the posteromedial bers of the anulus. ere
is an area of relative weakness in the posterolateral corners of
the disc, however, at the junction of the posterior longitudinal
ligament and uncinate process. As a result, it is the site of most
cervical disc herniations.20 According to Hayashi and colleagues,21 the posterior longitudinal ligament is double-layered,
and the deep layer sends bers to the anulus brosus and
continues laterally to the region of the intervertebral foramina.
e supercial or more dorsal layer of the posterior longitudinal ligament is adjacent to the dura mater and continues as
a connective tissue membrane, which envelops the dura mater,
nerve roots, and vertebral artery, suggesting that this membrane may serve as a protective barrier.
e ligamentum avum of the cervical spine attaches to the
anterior surface of the lamina above and to the superior
margin of the lamina below and extends laterally to the articular processes, contributing to the boundary of the intervertebral foramen. e ligamentum avum consists primarily of
elastic bers, whose numbers lessen with aging, resulting in
anterior buckling that can contribute to symptoms of spinal
cord compression. A gap in the midline of the ligamentum
avum allows for the exit of veins.
e interspinous ligament of the cervical spine is thin and
less well developed than in the lumbar region. It attaches in
an oblique orientation from the posterosuperior aspect to
the anteroinferior aspect of the spinous process. ere is no
separate supraspinous ligament in the cervical region. e
ligamentum nuchae, a broelastic septum, is the superior continuation of the supraspinous ligament of the thoracolumbar
spine and extends from the external occipital protuberance
to C7.
and posterior longitudinal ligaments and are rmly attached
to the adjacent vertebral endplates. e bers of the lamella
run perpendicular to the bers of the adjacent lamella. e
collagen bers in the posterior portion of the disc run more
vertical than oblique; this may account for the relative frequency of radial tears seen clinically. e discs are shaped to
conform to the surface of the bodies; the superior surface of
the disc is concave, and the inferior surface of the disc is
correspondingly convex in the coronal plane. e discs are
also slightly thicker anteriorly than posteriorly, which contributes to the lordotic posture of the cervical spine. e cervical
intervertebral discs allow some translational movement in the
sagittal plane, but the uncinate processes resist lateral movement. e uncinate process, located in the posterolateral
aspect of the disc, also helps prevent disc herniations in this
area. Degeneration of the anulus brosus (Fig. 18.4) in the
cervical region is similar to the lumbar region in that concentric, transverse, and radial tears of the anulus occur, and the
radial tear in the posterior aspect of the disc may be more
clinically signicant.
e cartilaginous endplate is a layer of hyaline cartilage
resting on the subchondral bone and serves as a barrier
between the pressure of the nucleus pulposus and the adjacent
vertebral bodies. is cartilage is a growth plate and responsible for endochondral ossication during growth (Fig. 18.5).
e cartilaginous endplates also allow the insertion of the
inner bers of the anulus brosus and the diusion of nutri-
ents from the subchondral bone to the disc.
Intervertebral Discs
Intervertebral discs are present between all vertebrae except at
the atlantoaxial level. Each intervertebral disc is an avascular
structure that consists of the nucleus pulposus at the interior
of the disc, the outer anulus brosus, and the cartilaginous
endplates adjacent to the vertebral surfaces. e nucleus pulposus functions as a shock absorber, and the anulus brosus
maintains the stability of the motion segment. With increasing
age, the margin between the nucleus pulposus and anulus
brosus becomes less distinct. Oen, by age 50 years, the
nucleus pulposus has become a brocartilaginous mass similar
to the inner zone of the anulus brosus.
e anulus has an outer collagenous layer, in which the
bers are arranged in oblique layers of lamellae. e outermost
bers of the anulus brosus are contiguous with the anterior
22
FIG. 18.4 Midsagittal cryomicrotome section of a degenerative cervical
spine showing degeneration of anulus brosus and herniation of nucleus
pulposus posteriorly with impingement of the spinal cord.
Chapter 18 Cervical Spine: Surgical Approaches 321
a
n
FIG. 18.5 Midsagittal microtome section of the cervical spine showing
nucleus pulposus (n) and outer anulus brosus (a) of the intervertebral disc.
Arrows identify a cartilaginous endplate.
Neural Elements
e cervical cord emerges from the foramen magnum as a
continuation of the medulla oblongata. ere is considerable
variation in size of the spinal cord; however, in general, owing
to the increased nerve supply to the upper limbs, the cervical
cord enlarges from C3 and becomes maximal at C6. Maximal
transverse diameters of 13 to 14 mm have been reported,23
with transverse areas ranging from 58.3 ± 6.7 mm3 at C624 to
85.8 ± 7.2 mm3 at C4–C5.
e spinal cord includes the outer white matter and the
inner gray matter. e white matter of the spinal cord contains
nerve bers and glia, and is divided into the posterior, lateral,
and anterior columns. e posterior column includes the
fasciculus cuneatus laterally and fasciculus gracilis medially,
mediating proprioceptive, vibratory, and tactile sensations.
e lateral column contains the descending motor lateral
corticospinal and lateral spinothalamic fasciculi. e anterior
funiculus contains the ascending anterior spinothalamic tract
and other descending tracts. e lateral spinothalamic tracts
cross through the ventral commissure to the contralateral side
of the cord, conveying pain and temperature sensations. e
anterior spinothalamic tract conveys the crude touch sensation.
e gray matter of the spinal cord contains cell bodies
of eerent and internuncial neurons. e somatosensory
neurons are located in the posterior horn, and the somatomotor neurons are found in the anterior horn of the gray
matter. e visceral center of the gray matter is found in the
intermediolateral horn. In the center of the spinal cord is the
central ependymal canal for the passage of cerebrospinal uid.
25
e spinal cord is covered by the pia mater, which is the
outer lining of the cord, and transparent arachnoid membrane
that contains the cerebrospinal uid. e dura mater is the
outer covering of the spinal cord, which becomes the inner
layer of the cranial dura at the level of the foramen magnum.
e cervical cord is anchored to the dura by the dentate ligaments that project laterally from the lateral side of the cord to
the arachnoid and dura at points midway between exiting
spinal nerves. By suspending the spinal cord in the cerebrospinal uid, the dentate ligaments cushion and protect the
cord, while minimizing the movement of the cord during
range of motion (ROM). e epidural space contains fat,
internal vertebral venous plexus, and loose connective tissue.
is venous plexus may be involved in spreading infection or
neoplasm. ere is a potential space between the dura and the
arachnoid, and the subarachnoid space is between the arachnoid and the pia. e subarachnoid space contains the cerebrospinal uid (CSF), spinal blood vessels, and nerve rootlets
from the spinal cord.
e dorsal sensory rootlets enter the cord through the
lateral longitudinal sulcus, and the ventral motor rootlets exit
the cord through the ventral lateral sulcus. e six or eight
rootlets at each level leave the spinal cord laterally to lie in
the lateral subarachnoid space bathed in the CSF. e rootlets
join to form the dorsal and ventral root, which together enter
a narrow sleeve of arachnoid and pass through the dura to
become a nerve root at each level. e cervical nerve roots
that form from the ventral and dorsal nerve rootlet extend
anterolaterally at a 45-degree angle to the coronal plane and
inferiorly at about 10 degrees to the axial plane.15 e nerve
roots enter the intervertebral foramina by passing directly laterally from the spinal canal adjacent to the corresponding disc
and over the top of the corresponding pedicle. e anterior
root lies anteroinferiorly adjacent to the uncovertebral joint;
the posterior root is close to the superior articular process.
e nerve root is positioned at the tip of the superior articular
process in the medial aspect of the neural foramen; it courses
more inferiorly to position over the pedicle in the lateral
aspect of the neural foramen (Fig. 18.6).
e roots occupy about one-third of the foraminal space in
the normal spine but much more in the degenerative spine.
e roots are located in the inferior half of the neural foramen
normally, but the nerve roots occupy a more cranial part of
the foramina, and the size of the foramen is diminished if the
neck is fully extended.26 e upper half of the neural foramen
contains fat and small veins.27 e nerve root is enlarged in
the distal aspect of the intervertebral foramen, and the dorsal
root ganglion is located just distal to the foramen.28 e dorsal
root ganglion is located between the vertebral artery and a
small concavity in the superior articular process. Just distal to
the ganglion and outside the intervertebral foramen, the
anterior and posterior roots join to form the spinal nerve. e
spinal nerve divides into dorsal and ventral primary rami
branches.
e gray rami from the sympathetic cervical ganglion join
the ventral primary rami. ere are interconnections between
gray rami, the perivascular plexus around the vertebral artery,
and the sympathetic trunk, all of which give contributions
SECTION
III
322 SURGICAL ANATOMY AND APPROACHES
FIG. 18.6 Parasagittal cryomicrotome section of the lateral aspect of the
neural foramen shows a nerve root coursing more inferiorly lying over a
pedicle as it begins to exit the foramen.
e second cervical nerve lies on the lamina of the axis
posterior to the lateral mass; the posterior primary ramus or
the greater occipital nerve pierces the trapezius about 2 cm
below the external occipital protuberance and 2 to 4 cm
from the midline. Trauma or irritation to any of the three
terminal nerves (the greater and lesser occipital nerve and
the greater auricular nerve) can produce pain, headache, or
hyperesthesia in their dermal distribution over the occiput
and around the ear.
Cutaneous branches of the posterior primary rami of C2–
C5 are consistently present in the skin of the nuchal region;
the largest cutaneous nerve in this region is the greater occipital nerve. e lesser occipital nerve is a branch from the
anterior cervical plexus, running upward and lateral to the
greater occipital nerve. e posterior primary ramus of C3, or
the third occipital nerve, pierces the trapezius more inferiorly
and about 1 cm medial from the midline. e cervical nerve
exits over the pedicle that bears the same number except the
C8 cervical nerve lies between the C7 and T1 vertebrae. e
posterior primary rami of cervical nerves send motor bers to
the deep muscles and sensory bers to the skin, but the rst
cervical nerve has no cutaneous branches. e anterior
primary rami of C1–C4 form the cervical plexus, and the rami
of C5–T1 form the brachial plexus.
Vascular Structures
to the ventral nerve plexus to innervate the anterior longitudinal ligament, outer anulus brosus, and anterior vertebral
29,30
body.
e dorsal nerve plexus receives contributions from
the sinuvertebral nerves, which originate from the gray rami
and perivascular plexus of the vertebral artery. e dorsal
nerve plexus innervates the posterior longitudinal ligament,
and the sinuvertebral nerves give branches to the posterior
part of the anulus and the ventral part of the dura. e
sinuvertebral nerves innervate two or more discs or motion
segments.
e rst cervical nerve or suboccipital nerve exits the
vertebral canal above the posterior arch of the atlas and posteromedial to the lateral mass, and lies between the vertebral
artery and the posterior arch. e posterior primary ramus
of the rst cervical nerve enters the suboccipital triangle
and sends motor bers to the deep muscles. e anterior
primary ramus of the rst cervical nerve forms a loop with
the second anterior primary ramus and sends bers to the
hypoglossal nerve. e cervical plexus receives bers from
anterior primary rami of C1–C4. e cervical plexus is located
opposite C1–C3, ventral and lateral to the levator scapulae and
middle scalene muscles. e cervical plexus has distributions
to the skin and muscles, such as the rectus capitis anterior
and lateralis, longus capitis and cervicis, levator scapulae, and
middle scalene. e cervical plexus forms loops and branches
to supply the sternocleidomastoid and trapezius muscles. It
has communications with the hypoglossal nerve from C1
and C2, and leaves this trunk as the superior root of the
ansa cervicalis, which is a nerve loop that is formed with the
inferior root from C2 and C3.
e major blood supply of the cervical cord and cervical spine
is the vertebral artery. Variations of the course of the vertebral
artery have been reported.31 In most cases, the vertebral artery
originates from the rst part of the subclavian artery and
begins its ascent behind the common carotid artery between
the longus colli and the anterior scalene. In the lower cervical
spine, the vertebral arteries are crossed by the inferior thyroid
artery and on the le by the thoracic duct. e vertebral arter-
ies course anterior to the ventral rami of the seventh and
eighth cervical nerves and the C7 transverse process before
entering the C6 transverse foramen, where they ascend within
the transverse foramen of C6–C2.
e surgeon should remember that the vertebral artery
is located lateral to the uncinate process and in line with
the middle one-third of the vertebral body just anterior to
the nerve root. During anterior exposure of the vertebral
body and intervertebral discs, too far lateral dissection on the
inferior half of the vertebral body and uncovertebral joints
would endanger the vertebral artery and spinal nerve around
the intervertebral foramen. e vertebral artery may also be
involved in patients with severe cervical spondylosis when it
may be impinged by the osteophyte. At the level of the atlas,
the artery winds posteromedially around the lateral mass and
over the posterior arch of the atlas before passing through
the posterior atlanto-occipital membrane into the foramen
magnum, joining the other vertebral artery to form the basilar
ar t er y.
In the foramen magnum region, the vertebral artery gives
branches anteriorly that join to form the single anterior spinal
artery, whereas the paired posterior spinal arteries are branches
from the posterior inferior cerebellar arteries. e anterior