Cổ tử cung Chẩn đoán và điều trị pot

Journal of the American Academy of Orthopaedic Surgeons
376
Cervical spondylosis results from
the nearly universal process of de-
generation of the disks and joints of
the cervical spine. These changes in
the spinal motion segments have
doubtless existed since the evolu-
tion of man, but our understanding
of the pathoanatomy and clinical
conditions associated with cervical
spondylosis is relatively recent.
Classic anatomic studies by Brain et
al
1
and Payne and Spillane
2
in the
1950s began to clarify the disease
process and its effect on the neural
elements. Surgical procedures
through a posterior approach for
decompression of the cervical spine
were available in the 1940s; how-
ever, decompression from an ante-
rior approach did not begin to be
used until the late 1950s. As cross-
sectional imaging evolved—with
computed tomographic (CT) scans
in the 1970s and later with magnetic
resonance (MR) imaging—a better

appreciation of the pathoanatomy
emerged.
A thorough understanding of the
pathology of cervical spondylosis,
as well as the principles of clinical
examination, radiologic evaluation,
and surgical indications, is essential
for optimal treatment planning.
Complications as a consequence of
the treatment of cervical spondylotic
myelopathy are intimately related
to the type and extent of surgical
procedure selected.
Natural History
Spinal cord compression resulting
from spondylotic changes in the cer-
vical spine is typically a slowly pro-
gressive process. Many patients
have evidence of significant com-
pression on neuroradiologic imag-
ing but are relatively asymptomatic.
It can be surprising how much
chronic deformation the spinal cord
can tolerate without interfering with
patient function (Fig. 1).
The natural history of cervical
myelopathy has been described in
classic papers by Lees and Turner
3
and Clarke and Robinson.

4
Lees
and Turner described exacerbation
of symptoms followed by often
long periods of static or worsening
function or, in rare instances, im-
provement. Very few patients had
Dr. Emery is Associate Professor, Department
of Orthopaedics, University Hospitals of
Cleveland Spine Institute, Cleveland, Ohio.
Reprint requests: Dr. Emery, University
Hospitals of Cleveland Spine Institute, Case
Western Reserve University, 11100 Euclid
Avenue, Cleveland, OH 44106.
Copyright 2001 by the American Academy of
Orthopaedic Surgeons.
Abstract
The delineation of cervical spondylotic myelopathy as a clinical entity has
improved with the development of high-quality cross-sectional neuroradiologic
imaging. The natural history of this disorder is usually slow deterioration in a
stepwise fashion, with worsening symptoms of gait abnormalities, weakness,
sensory changes, and often pain. The diagnosis can usually be made on the
basis of findings from the history, physical examination, and plain radiographs,
but confirmation by magnetic resonance imaging or computed tomography and
myelography is necessary. Minimal symptoms without hard evidence of gait
disturbance or pathologic reflexes warrant nonoperative treatment, but patients
with demonstrable myelopathy and spinal cord compression are candidates for
operative intervention. Both anterior and posterior approaches have been uti-
lized for surgical treatment of cervical myelopathy. Anterior decompression fre-
quently requires corpectomy at one or more levels and strut grafting with bone

from the ilium or fibula. Multilevel laminectomies were initially used for poste-
rior decompression but now are either combined with fusion or replaced by
laminoplasty. Any operative technique requires proper patient selection and
demands adequate decompression of the canal to effect neurologic improvement.
Perioperative complications can be devastating in this group of high-risk
patients with cervical spondylotic myelopathy, but careful attention to detail,
meticulous technique, and experience can result in excellent outcomes.
J Am Acad Orthop Surg 2001;9:376-388
Cervical Spondylotic Myelopathy:
Diagnosis and Treatment
Sanford E. Emery, MD
Sanford E. Emery, MD
Vol 9, No 6, November/December 2001
377
steady progressive deterioration.
Clarke and Robinson described a
similar stepwise pattern of decreas-
ing function. Long periods of sta-
ble neurologic function, sometimes
lasting for years, were noted in
about 75% of their patients. In the
majority, however, the condition
deteriorated between quiescent
streaks. About 20% of patients had
a slow, steady progression of symp-
toms and signs without a stable
period, and 5% had rapid deterio-
ration of neurologic function.
Generally, once moderate signs
and symptoms of myelopathy de-

velop, the ultimate prognosis is
poor. As cervical myelopathy has
become better understood, most
authors have recommended surgi-
cal intervention for patients with
moderate to severe myelopathy,
taking into account both the clinical
status and the neuroradiologic
findings, to alter this unfavorable
natural history.
Pathology
The pathoanatomy of cervical spon-
dylosis with myelopathy results
from the sequelae of the aging
process in the spine (i.e., disk de-
generation with hypertrophic os-
seous and ligamentous changes).
Disk desiccation is accompanied by
biochemical changes, with a relative
increase in the ratio of keratan sul-
fate to chondroitin sulfate. The loss
of elasticity and total disk substance
results in a decrease in disk height
with annular bulging. This altered
biomechanical environment stimu-
lates formation of chondro-osseous
spurs at the annular insertion near
the end-plates. The uncovertebral
joints hypertrophy, which may lead
Figure 1 Images of a 40-year-old man with severe cervical myelopathy who was able to ambulate with a walker and live independently

despite motor weakness in his arms and legs. He underwent an anterior corpectomy with strut graft and halo vest placement. Just prior
to discharge 1 week postoperatively, he died of an autopsy-proven acute coronary artery thrombosis. A, Sagittal MR image demonstrates
fixed subluxation of C3 on C4 with severe cord compression (arrowhead). B (top), Normal histologic cross section of the spinal cord at the
C2 level (above the compression). B (bottom), Histologic cross section of the spinal cord at the level of maximal compression. Note the
loss of central gray matter and disorganized architecture. Arrowheads identify the dura. (Reprinted with permission from Emery SE:
Cervical spondylotic radiculopathy and myelopathy: Anterior approach and pathology, in White AH, Schofferman JA [eds]: Spine Care.
St Louis: Mosby-Year Book, 1995, p 1370.)
A B
Cervical Spondylotic Myelopathy
Journal of the American Academy of Orthopaedic Surgeons
378
to foraminal stenosis. The posterior
zygoapophyseal joints can also be-
come arthritic, causing dorsal foram-
inal narrowing. Thickening of the
ligamentum flavum occurs, as well
as buckling of the flavum due to loss
of disk height. These degenerative
changes can result in cervical steno-
sis with spinal cord compression
(Fig. 2, A), often in concert with disk
protrusions or frank herniations.
Loss of cervical lordosis or even ky-
phosis may accentuate the problem.
Instability can be another cause of
cord impingement (Fig. 1). Cervical
spondylosis will typically result in
stiffening of the spinal motion seg-
ments. It is not uncommon for the
motion segments one or two levels

above the stiff segments to become
hypermobile. This is termed “com-
pensatory subluxation” (Fig. 2, B).
Identification of this feature is im-
portant and often requires flexion-
extension lateral radiographs. The
presence or absence of instability
will enter into the decision-making
process with regard to whether an
anterior or a posterior approach is
used, as well as the number of levels
requiring operative intervention.
Cervical kyphosis is not uncom-
mon in patients with significant
spondylotic changes. This deformity
will aggravate the degree of com-
pression in patients with cervical
stenosis or disk herniations because
the spinal cord will be stretched
over the posterior aspect of the disks
and vertebral bodies (Fig. 2, C). The
presence of kyphosis will typically
dictate an anterior operative ap-
proach to adequately decompress
the canal as well as to achieve an
improvement in the deformity,
which augments the direct decom-
pression.
Ossification of the posterior lon-
gitudinal ligament (OPLL) has also

been described as a cause of cervi-
cal myelopathy, with or without the
presence of spondylotic changes.
5
The etiology of this condition is
unknown. Genetic influences prob-
ably predominate, with certain
Asian populations, such as the
Japanese, having a higher incidence
of OPLL than others. The ossifica-
tion can be at one level, can involve
skip-type lesions at multiple levels,
or can be a continuous strip of bone
(Fig. 2, D). The ossified ligament is
often not a thin strip, but rather a
bulbous mass that may be centrally
or eccentrically located (Fig. 3). It
can occur in conjunction with cervi-
cal spondylosis and often produces
severe anterior compression of the
spinal cord. Long-standing OPLL
can ossify the adherent dura, which
may create the problem of spinal
fluid fistulae.
6
Another important anatomic fac-
tor underlying all of these patho-
logic conditions is the initial size of
the spinal canal.
7,8

There is a cer-
tain degree of variation in the size
of the space available for the spinal
cord, which is probably genetically
determined. In the midcervical
spine, the average midsagittal canal
diameter is 17 to 18 mm (range, 13
to 20 mm in the normal spine). Be-
cause spondylosis, disk herniations,
and OPLL take up space, a patient
with a congenitally narrow canal
will have a higher risk of cord com-
pression and myelopathy. Neck
extension decreases the spinal canal
diameter even further, and patients
can dynamically compress their
cords with neck motion. This phe-
nomenon is exemplified by a pa-
Figure 2 Causes of spinal cord compression in cervical spondylotic myelopathy. A, Cervical spondylosis with stenosis. B, Compensatory
subluxation. C, Cervical kyphosis. D, Ossification of the posterior longitudinal ligament (segmental and continuous types).
A B C D
Sanford E. Emery, MD
Vol 9, No 6, November/December 2001
379
tient with asymptomatic cervical
stenosis who sustains a hyperexten-
sion injury that results in acute pin-
cering of the spinal cord and central
cord syndrome.
In patients with spondylosis, a

canal measurement on a lateral plain
radiograph of 12 mm or less often
indicates cord compression, which
may or may not be symptomatic, as
the average diameter of the spinal
cord in the midcervical spine is 10
mm. However, plain radiographs
do not take into account soft-tissue
changes, such as disk herniations
and hypertrophied ligamentum
flavum, which can decrease the
space available for the cord. Fuji-
wara et al
9
correlated the transverse
area of the spinal cord as measured
on CT-myelography with the severity
of pathologic changes in cadaveric
spinal cords. Fujiwara et al
10
and
Koyanagi et al
11
have also found a
correlation between the preoperative
cross-sectional area of the cord and
the degree of postoperative recov-
ery; 30 mm
2
was found to be a

watershed mark, with patients hav-
ing poorer neurologic recovery if the
preoperative cross-sectional area
was below this value.
Pathophysiology of Spinal
Cord Compression
The pathoanatomic changes that
have been described have a direct
compressive effect on the neural
tissue with resultant spinal cord
ischemia. Ogino et al
12
examined
pathologic specimens and corre-
lated their findings with the degree
of cord compression. Mild to mod-
erate compression was associated
with degeneration of the lateral
white-matter tracts. More severe
compression led to necrosis of the
central gray matter. This occurred
when the ratio of the midsagittal
diameter of the deformed cord to
its width (the anterior-to-posterior
compression ratio) was less than
1:5. The authors noted that the
anterior white columns were rela-
tively resistant to infarction, even
in cases of severe compression.
Histologic changes associated

with myelopathy include axonal
demyelinization followed by cell
necrosis and gliosis or scarring
(Fig. 1, B). Cystic cavitation can
occur within the gray matter. This
more central destruction of the
cord tissue is probably related to
ischemic changes caused by defor-
mation of the cord. Breig et al
13
demonstrated that the vascular
supply of the gray matter was from
the transverse arterioles branching
out from the anterior spinal artery
system. With flattening of the cord
in an anterior-to-posterior direc-
tion, these transverse arterioles are
subject to mechanical distortion,
leading to relative ischemia of the
gray matter and medial white mat-
ter. The pathophysiologic effects of
cord compression are believed to
be a combination of ischemia and
direct mechanical effects on the
neural tissue.
The complex biochemical and cel-
lular mechanisms of acute spinal
cord injury are an area of active cur-
rent research. Chemical and cellular
mediators are being studied in both

acute spinal cord injury and amyo-
trophic lateral sclerosis to determine
the role of glutamate toxicity, free-
radical toxicity, cation-mediated cell
injury, and programmed apoptosis
(cell death) in both acute and pro-
gressive deterioration of neural tis-
sue. Further research may allow
investigators to relate these mecha-
nisms to the chronic changes that
occur with cervical myelopathy.
14
Clinical Presentation
Patients with cervical spondylosis,
either alone or in combination with
root or cord compression, can pre-
sent with a wide spectrum of clinical
signs and symptoms. Even patients
with cord compression may be com-
pletely asymptomatic with respect
to both pain and neurologic func-
tion. Others may have mild symp-
toms with only neck pain or some
component of radicular arm pain.
Paresthesias are common, typically
occurring in a global, nonderma-
tomal pattern in the upper extrem-
ities. Many patients with mye-
lopathy will not appreciate their
weakness; however, they may com-

Figure 3 Ossification of the posterior longitudinal ligament. A, Sagittal section from CT-
myelographic study shows an osseous bar behind two vertebrae spanning the C5-C6 disk
space. B, Cross-sectional view at C5 shows severe canal compromise from the asymmetri-
cal mass of OPLL extending from the posterior aspect of the vertebral body.
A B
Cervical Spondylotic Myelopathy
Journal of the American Academy of Orthopaedic Surgeons
380
plain of subtle changes in gait and
balance. This is often the first clue to
the presence of early myelopathy.
If the cord compression and
myelopathy are either moderate or
severe, patients complain of gait
and balance abnormalities involving
the lower extremities. They also
have numbness or paresthesias in
their upper extremities. Fine motor
control is usually affected as well,
and they will note changes in their
handwriting or ability to manipu-
late buttons or zippers. Arm weak-
ness is common in this group of
patients, either unilaterally or bilat-
erally. Leg weakness can occur, and
patients may notice problems mov-
ing their body weight, such as is
necessary when rising out of a chair
or going up stairs. In patients with
cervical myelopathy, the proximal

motor groups of the legs are more
involved than the distal groups
(which is the opposite of the pattern
with lumbar stenosis); thus, presen-
tation with foot-drop complaints is
rare. Changes in bowel or bladder
function can occur in extremely se-
vere cases of myelopathy, but this is
quite rare. Although most patients
with cervical spondylotic myelopa-
thy have neck pain, approximately
15% with moderate to severe mye-
lopathy do not. This may cause con-
fusion or a delay in diagnosis.
15
Spondylotic cord compression
can predispose a patient to spinal
cord injury (acute myelopathy) with
minor trauma. This typically occurs
in elderly patients who sustain a
fall that results in a hyperextension
neck injury. A central cord syn-
drome (motor weakness greater in
the arms than in the legs) often
ensues, with variable degrees of
paralysis. The patient may demon-
strate obvious weakness, prompt-
ing immediate evaluation and hos-
pitalization. At times, however, the
changes in the patient’s function

are minimal, and only with in-depth
history taking can one relate the de-
terioration to minor trauma.
Physical Examination
The clinical evaluation should be-
gin with an accurate description of
the onset of symptoms and the
time course over which they devel-
oped. Areas of neck tenderness
and range of motion should then
be evaluated. Neck extension is
generally restricted and may be
painful for patients with cervical
stenosis or root compression. This
is an important clinical feature and
may indicate a narrowed canal and
frank cord compression, which
may be extremely important for
patients undergoing procedures re-
quiring general anesthesia. Recog-
nition of the decreased extension
and stenosis may prevent iatro-
genic injury during intubation and
operative positioning.
A full neurologic examination is
critical to detect motor weakness
or sensory changes. Wasting of the
intrinsic muscles of the hand and
spasticity result in “myelopathy
hand.”

16
The “finger escape sign”
may be evident (Fig. 4, A). The pa-
tient is asked to hold his or her fin-
gers extended and adducted; if the
two ulnar digits drift into abduc-
tion and flexion in 30 to 60 sec-
onds, cervical myelopathy is con-
sidered to be present. Similarly,
the patient should be able to rapidly
make a fist and release it in a re-
petitive motion 20 times in 10 sec-
B
A
C D
Figure 4 A, Finger-escape sign. The patient holds his fingers extended and adducted. In
patients with cervical myelopathy, the two ulnar digits will flex and abduct, usually in less
than 1 minute. B, Grip-and-release test. Normally, one can make a fist and rapidly release
it 20 times in 10 seconds; patients with myelopathy may be unable to do this that quickly.
C, Hoffmann reflex. Snapping the distal phalanx of the patient’s middle finger downward
will result in spontaneous flexion of the other fingers in a positive test. D, Inverted radial
reflex. Tapping the distal brachioradialis tendon produces hyperactive finger flexion.
Sanford E. Emery, MD
Vol 9, No 6, November/December 2001
381
onds (Fig. 4, B); slow or clumsy
performance on this grip-and-
release test is consistent with cervi-
cal cord compression.
Wasting of the shoulder girdle

may be evident in patients with
stenosis at C4-5 and C5-6 due to loss
of anterior-horn cell function. This
dropout of motor neurons may also
manifest as fasciculation in the
upper-extremity muscles. This is a
nonspecific finding, however, and
can be present in degenerative
upper motor neuron diseases, such
as amyotrophic lateral sclerosis.
Pinprick examination should be
done in the upper and lower extrem-
ities, looking for a global decrease in
sensation, dermatomal changes, and
dysesthesias. Vibratory testing is
performed to test the function of the
posterior columns. This finding, if
present, is typically found in severe
cases of long-standing myelopathy.
Vibratory testing is also utilized to
help detect concomitant changes
due to peripheral neuropathy, such
as may be noted in patients with
diabetes, thyroid disease, or heavy
alcohol use.
Reflex examination should show
hyperreflexia in both the upper and
the lower extremities, although
severe concomitant cervical root
compression may result in an absent

reflex in one or more muscle groups.
Clonus and positive Babinski and
Hoffmann reflexes (Fig. 4, C) are
abnormal long-tract signs consistent
with cord compression. These are
found in varying degrees in patients
with moderate to severe myelopa-
thy. The inverted radial reflex is an-
other pathologic change sometimes
evident in patients with cervical
stenosis and myelopathy. If tapping
the brachioradialis tendon in the dis-
tal forearm elicits a hypoactive bra-
chioradialis reflex plus hyperactive
finger flexion, this is a positive radial
reflex. This correlates with cord and
C5 root lesions that produce spastic-
ity distal to the compression and a
hypoactive response at the level of
root or anterior horn cells (Fig. 4, D).
Cranial nerve abnormalities or a
hyperactive jaw jerk can suggest a
cranial or brainstem lesion, which
should be evaluated with brain
imaging and neurologic consul-
tation.
Patients with cervical complaints
should have their gait examined for
ability to toe-walk, heel-walk, and
perform a toe-to-heel tightrope gait.

Subtle myelopathy may be evident
on this provocative testing. The
Romberg test, in which the patient
stands with the arms held forward
and the eyes closed, is a test for
position sense; loss of balance is
a positive result consistent with
posterior-column dysfunction.
Radiologic Evaluation
Radiographic changes of cervical
spondylosis are age-related and
occur in most people over the age
of 50. Typical radiographic mani-
festations include disk-space nar-
rowing, end-plate sclerosis, and
osteophytic changes at the end-
plates, uncovertebral joints, and
facet joints. Plain radiographs re-
main an important part of the
diagnostic workup, and anteropos-
terior (AP), lateral, and flexion-
extension views of the cervical
spine should be obtained in essen-
tially all patients in this age group.
Oblique views are useful for visual-
izing foraminal narrowing, which is
typically due to uncovertebral joint
spurs; however, the true utility of
oblique views in evaluation of de-
generative conditions is question-

able. The AP view allows identifi-
cation of cervical ribs and scoliotic
deformity. The lateral view is most
important, as it demonstrates the
degree of disk narrowing, the size
of end-plate osteophytes, the size of
the spinal canal, and sagittal align-
ment. In some cases, OPLL is visu-
alized as a bar of bone running
along the posterior aspect of the
vertebral bodies. Overall sagittal
alignment (lordosis versus kypho-
sis) is also important in that it may
influence the choice of surgical pro-
cedure. Flexion-extension views
are critical to diagnose instability,
which may not be evident on a
neutral lateral view. Patients with
stiffening of the midcervical spine
from spondylotic changes often
have a compensatory subluxation
one or two levels above the stiffer
levels.
Magnetic resonance imaging is
the next step in the evaluation of
the patient with a presumed diag-
nosis of spondylosis with myelopa-
thy. However, this modality is cer-
tainly not indicated for everyone
who presents with neck pain. Per-

sistent neck or arm pain (present
for more than 2 or 3 months), neuro-
logic findings, or a worsening symp-
tomatic picture warrants neuroradio-
logic investigation. If evidence of
myelopathy is present on physical
examination, MR imaging is indi-
cated to assess the extent of patho-
logic changes to the soft tissues
(e.g., disk herniation, hypertrophy,
and buckling of the ligamentum
flavum) and the degree of cord
compression. One of the strengths
of MR imaging is the ability to visu-
alize the spinal cord. The size and
shape of the cord are evident on
both sagittal and transverse images.
Flattening of the cord over anterior
compressive lesions, such as osteo-
phytic ridging, OPLL, disk hernia-
tions, and kyphotic deformities, can
be seen. In long-standing cases of
compression, cord atrophy is evi-
dent. It is important to identify pa-
renchymal changes, such as syrinx
formation, or high-intensity signal
within the cord resulting from mye-
lomalacia. Although high-intensity
signal change does not necessarily
correlate with preoperative deficits

or postoperative recovery, it certainly
identifies pathologic changes within
the cord that should alert the treat-
ing physician.
Cervical Spondylotic Myelopathy
Journal of the American Academy of Orthopaedic Surgeons
382
Although MR imaging provides
optimal visualization of soft tissues,
CT-myelography offers better defi-
nition of bone spurs and OPLL. The
exact degree of cord deformation in
the transverse plane is more sharply
visualized with CT-myelography
as well. This modality is useful in
evaluating whether marginal levels
need to be included in an operative
procedure.
Other forms of clinical evalua-
tion include electrodiagnostic tech-
niques. For patients with cervical
radiculopathy, electromyographic–
nerve conduction studies may be
useful in considering the differen-
tial diagnosis of carpal tunnel syn-
drome, ulnar cubital tunnel syn-
drome, or thoracic outlet syndrome.
Electrodiagnostic modalities may
also help elucidate the confusing
clinical presentations of amyotrophic

lateral sclerosis, multiple sclerosis,
and severe peripheral neuropathy.
Somatosensory-evoked poten-
tials and motor-evoked potentials
are of limited utility during the
diagnostic evaluation but are used
intraoperatively. A preoperative
baseline study can be very helpful,
especially in patients with severe
changes in latency and amplitude.
Some authors advocate the use of
intraoperative spinal-cord evoked
potentials to identify the level of
greatest conduction delay and then
limit surgery to that level
17
; how-
ever, this approach risks leaving
clinically significant pathologic
changes in untreated areas.
Nonoperative Treatment
Patients with neuroradiologic evi-
dence of spinal cord compression
but no symptoms or signs of mye-
lopathy should generally be ob-
served. One exception would be a
patient with such severe compres-
sion that even low-energy trauma,
such as might occur with a rear-end
motor vehicle impact or a fall, could

predictably result in spinal cord
injury. It is extremely rare for a pa-
tient with that degree of cord com-
pression on imaging studies to be
truly asymptomatic; nevertheless,
these patients should be counseled to
avoid high-risk situations in which a
hyperextension injury might occur,
as they are at some increased risk for
cord impingement.
Patients with mild myelopathy
may display findings such as slight
gait disturbance and mild hyper-
reflexia but may have no functional
deficits and no weakness. The indi-
vidual clinical course and especially
the pattern of deteriorations should
be well understood by both physi-
cian and patient. If the patient is in
a plateau period without recent ex-
acerbation, nonoperative treatment
may be indicated. Reevaluation
every 6 to 12 months to look for de-
terioration of neurologic function or
a change in symptoms may be ap-
propriate.
Indications for Surgery
The natural history of cervical
myelopathy for most patients is
slow deterioration over time. Typ-

ically, this is in a stepwise fashion
with variable periods of stable neuro-
logic function. If one assumes sig-
nificant deterioration for all pa-
tients with myelopathy, it can be
argued that operative intervention
is indicated for everyone with this
clinical and radiographic diagnosis.
However, the decision making is
much more complex, with the clini-
cal severity of myelopathy being
the most important issue.
The extent of myelopathy is
reflected predominantly by physi-
cal examination findings such as
balance deficits, gait, motor weak-
ness, long-tract signs, and changes
in function (e.g., decreased fine
motor control). All of these clinical
findings provide evidence of the
degree of cord dysfunction. Other
important factors involved in the
decision-making process include
the amount of pain the patient is
experiencing, the degree of change
of function that can be tolerated,
and the evaluation of symptoms.
Patients with rapid neurologic de-
terioration should undergo earlier
operative intervention.

Consideration of the severity of
compression evident on neuroradio-
logic studies is important, as the
severity of cord compression gener-
ally, but not always, correlates with
the level of function. For patients
with equivalent signs and symp-
toms of moderate myelopathy,
operative intervention would be
recommended earlier if there were
more severe radiologic findings,
such as smaller cord area, cord atro-
phy, signal changes indicative of
myelomalacia, or the presence of a
kyphotic deformity. Although not
all neuroradiologic findings have
been correlated with preoperative
symptoms or postoperative out-
come, more severe compression
intuitively suggests more risk for
the spinal cord.
For patients with moderate to se-
vere compression and myelopathy,
surgical intervention is indicated to
alter the natural history. Surgery
can be expected to halt progression
in neurologic function and may
improve motor, sensory, and gait
disturbance. The degree of recovery
depends largely on the severity of

the myelopathy at the time of inter-
vention.
10,15
Other factors of posi-
tive prognostic value include larger
transverse area of the cord, younger
patient age, shorter duration of
symptoms, and single rather than
multiple levels of involvement.
10,11
Many patients with cervical spon-
dylosis and myelopathy are elderly,
but age alone is not a contraindica-
tion to operative intervention.
Patients with chronic cervical
spondylosis who suffer acute minor
trauma, particularly a hyperexten-
sion injury, can sustain acute spinal
Sanford E. Emery, MD
Vol 9, No 6, November/December 2001
383
cord injuries of varying severity
superimposed on the long-standing
myelopathy. Typically, this pre-
sents as a central cord syndrome
with greater weakness in the upper
extremities than in the lower ex-
tremities and proximal rather than
distal muscle involvement in each
extremity. This can occur with or

without a prior history of myelo-
pathic symptoms. Initial treatment
involves collar immobilization,
high-dose methylprednisolone, and
a neuroradiologic investigation. If
neurologic function improves after
the injury, the plateau functional
level should be determined. If re-
covery is complete or near com-
plete, surgery is not necessary.
Residual deficits, as evidenced by
the appearance of cord compression
on imaging studies, warrant opera-
tive intervention to promote neuro-
logic recovery. One recent long-
term study of patients with central
cord syndrome treated nonopera-
tively documented much poorer
recovery in patients over 50 years of
age compared with younger pa-
tients.
18
There are no data docu-
menting a substantial difference in
recovery if diagnosis was early
rather than late.
Surgical Approaches
The preferred approach for surgical
treatment of cervical myelopathy
continues to be controversial, as

both anterior and posterior tech-
niques have been used successfully.
Posterior options include multilevel
laminectomy,
19
laminoplasty, and
laminectomy plus fusion proce-
dures. Anterior options include
multiple anterior diskectomies
with fusion and corpectomy plus
strut fusion techniques with or
without the use of anterior instru-
mentation. The choice of approach
is determined on the basis of the
existing lesion and surgeon experi-
ence. Factors to be considered in-
clude the number of involved lev-
els, overall sagittal alignment, the
direction of compression, the pres-
ence of instability, and clinical
symptoms.
Posterior Approach
For patients with diffuse canal
stenosis or dorsal cord compres-
sion due to buckling of the liga-
mentum flavum posteriorly, a pos-
terior decompression technique may
be ideal to achieve adequate decom-
pression (Fig. 5). However, most
patients with cervical spondylosis

and certainly those with OPLL
have predominantly anterior com-
pression of the cervical cord. Any
posterior decompressive procedure
is an indirect technique that re-
quires posterior shifting of the cord
in the thecal sac to diminish the
effect of the anterior compression.
For this to occur, the preoperative
sagittal alignment of the cervical
spine must be at least straight or
preferably lordotic. A kyphotic spine
is less likely to allow sufficient pos-
terior translation of the spinal cord
to diminish symptoms. This is a
key point in choosing between pos-
terior and anterior approaches for
surgical treatment of myelopathy,
as is the presence of instability.
Laminectomy alone will only wors-
en preexisting instability. Fusion
must be added if the posterior ap-
proach is the preferred route of de-
compression.
Multilevel laminectomy was ini-
tially the only procedure available
to treat cervical stenosis and may
still have a place for selected pa-
tients. The results after that proce-
dure deteriorate due to the devel-

opment of late instability, such as
kyphosis or subluxation, although
A B C
Figure 5 Images of a 61-year-old man with moderate cervical spondylotic myelopathy, gait changes, upper-extremity neurologic signs
and symptoms, and minimal neck pain. A, Sagittal MR image shows normal lordosis and suggests diffuse narrowing of the spinal canal
over multiple levels. B, Axial CT-myelographic image at C5 shows severe stenosis that is causing circumferential, rather than focal anteri-
or, cord impingement. C, The patient underwent a laminoplasty from C3 to C7 performed with use of the Chiba method. A postoperative
CT image demonstrates expansion of the spinal canal at C4. The clinical outcome at 3-year follow-up was rated as successful.
Cervical Spondylotic Myelopathy
Journal of the American Academy of Orthopaedic Surgeons
384
the exact incidence of this problem
is difficult to determine. The addi-
tion of a multilevel fusion at the
time of laminectomy eliminates the
potential for development of late
postoperative kyphosis or instabil-
ity. Although originally done with
bone graft wired to the facets, it is
now more easily achieved by lateral
mass plating and fusion.
Laminoplasty evolved as a method
to eliminate postoperative develop-
ment of instability and kyphosis by
expanding the canal while retaining
the posterior elements.
20,21
Several
techniques for performing lamino-
plasty have been devised, but all

adhere to the concept of canal ex-
pansion by opening the posterior
elements in a trapdoor fashion but
not completely removing the osse-
ous posterior arch. By expanding
the size of the canal, the cord com-
pression can be alleviated or less-
ened, and the chance of postopera-
tive instability is minimized because
the posterior musculature can heal
to the residual posterior osseous ele-
ments. Most methods are based on
either a unilateral hinge with a one-
way trapdoor opening to expand
the canal
20
or a midline spinous
process–splitting procedure with
bilateral hinges to expand the canal
in a symmetrical fashion.
22,23
A
small amount of bone graft or spacer
is often placed in the opening de-
fects, but arthrodesis of the motion
segments is not desirable. Lamino-
plasty results in a 30% to 50% loss
of motion in the cervical spine,
23,24
which is less than occurs with mul-

tilevel arthrodesis.
Anterior Approach
Because the pathoanatomy of
cord compression in degenerative
conditions is typically anterior to
the spinal cord, an anterior ap-
proach allows direct decompres-
sion of the dura (Fig. 6). Two dif-
ferent techniques can be utilized,
with selection dependent on align-
ment and the pathologic features.
If the cord compression is present
only at the disks at one, two, or
three levels, an anterior cervical
diskectomy with graft at each level
is appropriate. In most patients
with spondylotic myelopathy or
OPLL, there is compression at the
disk as well as above and below the
disk space. Usually, this is caused
by large osteophytes or ridging at
the vertebral end-plates. Ossifica-
tion of the posterior longitudinal
ligament occurs behind the verte-
bral body and may be focal or mul-
tifocal or may appear as a continu-
ous long osseous bar. Because the
surgeon cannot safely reach poste-
rior to the vertebral bodies through
the disk space, it is necessary to

remove part or all of the midpor-
tion of the vertebral body to ade-
quately decompress the canal.
A
C
B
D
Figure 6 A, Sagittal T2-weighted MR image demonstrates spondylotic changes with
severe spinal cord compression predominantly at two levels. B, Postoperative CT scan
demonstrates decompression of the spinal canal and the fibular graft. C, Lateral radio-
graph obtained immediately after two-level anterior cervical corpectomies and fibular
strut grafting (arrowheads). D, Lateral radiograph obtained 2 years later shows smooth
bone remodeling, indicating a solid arthrodesis.
Sanford E. Emery, MD
Vol 9, No 6, November/December 2001
385
Hemicorpectomies may be per-
formed for end-plate osteophytes
located near the disk spaces; how-
ever, full corpectomies are more
commonly performed to totally
decompress the canal at several
disk levels as needed. The lateral
walls of the vertebral body are left
intact because they provide protec-
tion against vertebral artery injury.
The typical midline channel for a
corpectomy is 16 to 18 mm, which
provides adequate decompression
for the entire canal if it is appropri-

ately centered in the midline.
It is not uncommon for a patient
with cervical spondylotic myelopa-
thy to require a two- or three-level
corpectomy and then a strut graft
for fusion or to correct kyphosis.
The degree of difficulty of the proce-
dure, the risk of postoperative graft
complications, and the potential for
soft-tissue complications increase
with the number of corpectomy lev-
els. This limitation should enter into
the decision-making process regard-
ing choice of approach.
Autograft, allograft, and even
metal cages with cancellous grafts
have been used as struts to main-
tain alignment and promote ar-
throdesis. Autografts provide the
highest union rate. Harvesting
large iliac-crest grafts may be asso-
ciated with local pain, fracture of
the ilium, and injury to the lateral
femoral cutaneous nerve. Autol-
ogous fibular grafts have been asso-
ciated with less morbidity than long
iliac grafts, although tibial stress
fractures,
25
pain, and muscle weak-

ness
26
have been described. Allo-
graft iliac-crest or fibular grafts are
used for single-level diskectomy
and fusion, with good success rates
reported in most studies
27
but less
optimal results in others.
28
Fibular
strut allografts have also been used
successfully
29
for reconstruction
after multilevel corpectomy but are
slower to heal and have a higher
rate of pseudarthrosis. Some sur-
geons use cancellous chips from the
vertebrectomy to augment the allo-
graft; others prefer supplemental
posterior fixation combined with
anterior allograft struts to promote
union. Many surgeons utilize iliac-
crest strut grafts for one- or two-
level vertebrectomy procedures and
fibular strut grafts for constructs to
be used at two or more levels.
Theoretically, the use of anterior

cervical plates provides additional
stability, maintains correction of
deformity, and promotes arthrode-
sis, especially in longer or multilevel
constructs. There is considerable
controversy concerning the use of
plates for one-level anterior cervical
diskectomy and fusion, unless there
are certain coexisting circumstances,
such as a history of smoking or the
presence of adjacent segment fu-
sions. Anterior plate fixation after
one-level corpectomy (two-level
fusion) with iliac-strut fusion pro-
vides increased stability and may
allow less restrictive immobilization
postoperatively.
The use of anterior plates for
multilevel corpectomy and strut-
graft procedures is more controver-
sial. Because of the long lever arm
with only two screws above and
two screws below, a high rate of
loosening and displacement has
been described for these long-plate
constructs.
30
Three-level corpectomy
procedures seem to be at higher
risk for this complication than two-

level procedures. Also, plate fixa-
tion does not allow settling of the
graft into the vertebral-body dock-
ing sites, which may actually inhibit
arthrodesis. Other authors have
utilized a small buttress-type plate
at the inferior end of the strut-graft
construct to help prevent graft dis-
lodgment. Failures with this tech-
nique have also been reported.
31
Meticulous preparation of the ver-
tebral bodies, including centralizing
the graft in the end-plate with
sculpted mortices, will help mini-
mize complications due to graft dis-
lodgment.
Choice of Approach
For each patient, the surgeon
should weigh the relative advan-
tages and disadvantages of the
anterior and posterior approaches.
Neither is optimal for every patient
with cervical spondylotic myelopa-
thy, although either may be appro-
priate for some patients. The rela-
tive pros and cons of laminoplasty
versus anterior corpectomy and
strut grafting are summarized in
Table 1.

Anterior decompression and
arthrodesis is a more direct decom-
pression method that allows cor-
rection of deformity and stabiliza-
tion with fusion. It is technically
demanding, especially in multi-
level cases, and one must be pre-
pared to deal with graft-related
complications. Rigid postoperative
bracing is necessary with an ortho-
sis or a halo vest.
The posterior approach is an in-
direct method of decompression in
most cases and relies on the spinal
cord being able to shift posteriorly
in an expanded canal. For this rea-
son, patients with preoperative
kyphosis are not good candidates
for a posterior unroofing-type pro-
cedure because the anterior im-
pingement on the cord will remain.
Compensatory subluxation or other
instability may also worsen with a
posterior approach if fusion is not
performed.
Laminoplasty techniques are not
as technically demanding as multi-
level anterior corpectomy and strut-
grafting procedures. There is less
bracing required, as a soft collar will

generally suffice for comfort after
laminoplasty. Although some loss
of motion is typical after lamino-
plasty procedures, this would be
expected to be less than occurs with
long arthrodesis methods. More re-
cent data have suggested that lami-
noplasty techniques may not provide
consistent relief of axial neck pain,
32
whereas anterior fusion procedures
provide good axial pain relief.
15
Cervical Spondylotic Myelopathy
Journal of the American Academy of Orthopaedic Surgeons
386
The preoperative symptoms play
a role in the decision-making pro-
cess as well. Patients with diffuse
canal stenosis and a congenitally nar-
row canal may require decompres-
sion of virtually the entire cervical
spine. This is more readily achieved
with laminoplasty techniques. Some
authors prefer the anterior approach
for patients with pathologic changes
at one or two levels and posterior
surgery for those with involvement
at three or more levels.
33

With prop-
er patient selection, both anterior
and posterior techniques will pro-
vide comparable rates of neurologic
recovery and improvement of func-
tion.
34,35
There are cases in which anterior
multilevel decompression and strut
grafting followed by posterior stabi-
lization is indicated. Postlaminec-
tomy kyphosis is perhaps the best
example of this. Anterior decom-
pression will typically be needed
because of the degree of deformity
and anterior-cord compression.
Prior removal of the posterior ele-
ments predisposes them to graft
complications if only an anterior
approach is performed
36
; immediate
posterolateral mass plating will help
protect the graft, maintain alignment,
and promote successful arthrodesis.
The circumferential approach is also
preferable for patients with severe
osteoporosis, because it avoids frac-
ture of the inferior end-plate due to
loading by the graft. In multilevel

cases requiring corpectomies at
three or more levels, supplemental
posterior fixation may increase
fusion rates and decrease compli-
cations.
Complications
Complications can generally be cat-
egorized as: (1) approach-related,
(2) decompression-related, (3) graft-
related, and (4) long-term. Risks
incurred with the anterior approach
to the cervical spine include stretch
injuries to the recurrent laryngeal
nerve, which produce hoarseness.
The incidence of this injury is be-
lieved to be approximately 1% to
2%.
37
Dysphagia is experienced
transiently by most patients after an
anterior surgical approach, but can
be a persistent problem for some.
Upper airway compromise from
edema or hematoma formation is
more likely after multilevel corpec-
tomy procedures.
38
Drains should
be utilized, and patients frequently
are monitored for 24 to 48 hours

postoperatively. The airway should
be evaluated before extubation
to minimize the risk of airway ob-
struction.
Both nerve root and spinal cord
injury may occur during the decom-
pression. Good visualization, care-
ful technique, and experience are
mandatory to avoid devastating
results. The incidence of neurologic
injury is approximately 1% to 2%.
15
Spinal cord monitoring should be
used for most, if not all, of these
procedures. Corticosteroids may be
given prophylactically in high-risk
cases. During the procedure, any
change in spinal cord monitoring
considered to be significant should
be treated with the same dose of
methylprednisolone used for trau-
matic spinal cord injury (loading
dose of 30 mg per kilogram of body
weight, followed by 5.4 mg/kg per
hour for 23 hours).
Motor palsy of the C5 root in
patients who have undergone lami-
noplasty procedures has been well
described. The etiology of this post-
operative deficit is not clear but is

thought to be related to the short
length of the C5 root and the maxi-
mal lordosis at that level; when the
spinal cord shifts posteriorly after
decompression, the C5 root is be-
lieved to sustain a stretch injury.
The incidence of this complication is
1% to 3%,
24
and slow but progres-
sive recovery has been reported in
most, but not all, patients. C5 root
palsy can also occur following ante-
Table 1
Advantages and Disadvantages of Anterior and Posterior Approaches
Anterior Approach Posterior Approach
Advantages 1. Direct decompression 1. Less loss of motion
2. Stabilization with arthrodesis 2. Not as technically demanding
3. Correction of deformity 3. Less bracing needed
4. Axial lengthening of spinal column 4. Avoids graft complications
5. Good axial pain relief
Disadvantages 1. Technically demanding 1. Indirect decompression
2. Graft complications 2. Preoperative kyphosis and/or instability
3. Need for postoperative bracing limitations
4. Loss of motion 3. Inconsistent axial pain results
5. Adjacent segment degeneration 4. Late instability
Sanford E. Emery, MD
Vol 9, No 6, November/December 2001
387
rior decompression and fusion pro-

cedures but is relatively rare.
Injury to the vertebral artery is
also possible during anterior verte-
bral corpectomies.
39
Strict orienta-
tion to the midline is necessary to
help avoid this complication. Man-
agement includes exposure of the
artery above and below the corpec-
tomy, with ligation or microscopic
repair. Spinal fluid leaks can occur
during both anterior and posterior
procedures. Because patients with
long-standing OPLL may have ero-
sion of the dura,
6
gelatin-foam
sponge and fibrin glue, fascial patch-
ing, or a lumbar cerebrospinal fluid
drain may be needed to prevent a
persistent fistula.
40
Graft-related complications after
an anterior strut-graft procedure may
include dislodgment, fracture, and
severe settling into the cancellous
bone of the vertebral bodies. With
long fibular grafts, the docking site
in the inferior vertebral body can

split due to axial loading, and the
inferior end of the graft can displace
anteriorly. If there is no longer bone
contact, if the esophagus is threat-
ened, or if significant kyphosis en-
sues, operative revision is indicated.
Long-term complications from
anterior decompression and ar-
throdesis procedures include pseud-
arthrosis and adjacent-segment
degeneration. Patients with recur-
rent myelopathy should be evaluated
for pseudarthrosis and for compres-
sion at levels adjacent to the long
fusion that have undergone further
degenerative changes. It appears to
be true that fusions accelerate spon-
dylotic changes at adjacent disk lev-
els; however, a recent study sug-
gests it may not be higher than
would be attributable to the natural
history of spondylosis.
41
Laminectomy procedures are
associated with an increased risk of
postlaminectomy kyphosis, swan-
neck deformity, or instability with
late neurologic deterioration. Lami-
noplasty techniques decrease these
risks, but add the potential compli-

cation of inadvertent closure of the
opened lamina with recurrent ste-
nosis. Incomplete decompression
may necessitate a second-stage ante-
rior procedure.
Summary
Operative intervention for cervical
myelopathy has consistently been
shown to improve the neurologic
function of a high percentage of
patients. Neurologic outcomes ap-
pear to improve to a similar degree,
regardless of whether anterior or
posterior techniques are utilized,
provided the guidelines discussed
earlier are taken into consideration.
As with other types of spine
surgery, careful patient selection
remains the cornerstone of good
surgical results. This, combined
with high-quality imaging studies
and meticulous surgical technique,
will result in gratifying results with
respect to neurologic recovery,
function, and pain relief.
Acknowledgment: The author wishes to
thank Val Schmedlen for her assistance in
the preparation of the manuscript.
References
1. Brain WR, Northfield D, Wilkinson M:

The neurological manifestations of cer-
vical spondylosis. Brain 1952;75:187-225.
2. Payne EE, Spillane JD: The cervical
spine: An anatomico-pathological
study of 70 specimens (using a special
technique) with particular reference to
the problem of cervical spondylosis.
Brain 1957;80:571-596.
3. Lees F, Turner JWA: Natural history
and prognosis of cervical spondylosis.
BMJ 1963;2:1607-1610.
4. Clarke E, Robinson PK: Cervical
myelopathy: A complication of cervi-
cal spondylosis. Brain 1956;79:483-510.
5. Tsuyama N: Ossification of the poste-
rior longitudinal ligament of the spine.
Clin Orthop 1984;184:71-84.
6. Smith MD, Bolesta MJ, Leventhal M,
Bohlman HH: Postoperative cere-
brospinal-fluid fistula associated with
erosion of the dura: Findings after
anterior resection of ossification of the
posterior longitudinal ligament in the
cervical spine. J Bone Joint Surg Am
1992;74:270-277.
7. Wolf BS, Khilnani M, Malis L: The
sagittal diameter of the bony cervical
spinal canal and its significance in cer-
vical spondylosis. J Mt Sinai Hosp
1956;23:283-292.

8. Arnold JG Jr: The clinical manifesta-
tions of spondylochondrosis (spondy-
losis) of the cervical spine. Ann Surg
1955;141:872-889.
9. Fujiwara K, Yonenobu K, Hiroshima
K, Ebara S, Yamashita K, Ono K:
Morphometry of the cervical spinal
cord and its relation to pathology in
cases with compression myelopathy.
Spine 1988;13:1212-1216.
10. Fujiwara K, Yonenobu K, Ebara S,
Yamashita K, Ono K: The prognosis of
surgery for cervical compression
myelopathy: An analysis of the factors
involved. J Bone Joint Surg Br 1989;71:
393-398.
11. Koyanagi T, Hirabayashi K, Satomi K,
Toyama Y, Fujimura Y: Predictability
of operative results of cervical com-
pression myelopathy based on preop-
erative computed tomographic myel-
ography. Spine 1993;18:1958-1963.
12. Ogino H, Tada K, Okada K, et al:
Canal diameter, anteroposterior com-
pression ratio, and spondylotic mye-
lopathy of the cervical spine. Spine
1983;8:1-15.
13. Breig A, Turnbull I, Hassler O: Effects
of mechanical stresses on the spinal
cord in cervical spondylosis: A study

on fresh cadaver material. J Neurosurg
1966;25:45-56.
14. Fehlings MG, Skaf G: A review of the
pathophysiology of cervical spondy-
lotic myelopathy with insights for
potential novel mechanisms drawn
from traumatic spinal cord injury.
Spine 1998;23:2730-2737.
15. Emery SE, Bohlman HH, Bolesta MJ,
Jones PK: Anterior cervical decom-
pression and arthrodesis for the treat-
Cervical Spondylotic Myelopathy
Journal of the American Academy of Orthopaedic Surgeons
388
ment of cervical spondylotic myelopa-
thy: Two to seventeen-year follow-up.
J Bone Joint Surg Am 1998;80:941-951.
16. Ono K, Ebara S, Fuji T, Yonenobu K,
Fujiwara K, Yamashita K: Myelopathy
hand: New clinical signs of cervical
cord damage. J Bone Joint Surg Br
1987;69:215-219.
17. Tani T, Ishida K, Ushida T, Yamamato
H: Intraoperative electroneurography
in the assessment of the level of opera-
tion for cervical spondylotic myelopa-
thy in the elderly. J Bone Joint Surg Br
2000;82:269-274.
18. Newey ML, Sen PK, Fraser RD: The
long-term outcome after central cord

syndrome: A study of the natural histo-
ry. J Bone Joint Surg Br 2000;82:851-855.
19. Epstein JA, Janin Y, Carras R, Lavine
LS: A comparative study of the treat-
ment of cervical spondylotic myelo-
radiculopathy: Experience with 50 cases
treated by means of extensive laminec-
tomy, foraminotomy, and excision of
osteophytes during the past 10 years.
Acta Neurochir (Wien) 1982;61:89-104.
20. Hirabayashi K, Satomi K: Operative
procedure and results of expansive
open-door laminoplasty. Spine 1988;
13:870-876.
21. Kimura I, Shingu H, Nasu Y, Shiotani
A, Oh-hama M, Murata M: Long-term
follow-up of cervical spondylotic
myelopathy treated by canal-expan-
sive laminoplasty. J Bone Joint Surg Br
1995;77:956-961.
22. Tomita K, Kawahara N, Toribatake Y,
Heller JG: Expansive midline T-Saw
laminoplasty (modified spinous
process-splitting) for the management
of cervical myelopathy. Spine 1998;23:
32-37.
23. Edwards CC II, Heller JG, Silcox DH
III: T-Saw laminoplasty for the man-
agement of cervical spondylotic
myelopathy: Clinical and radiographic

outcome. Spine 2000;25:1788-1794.
24. Satomi K, Nishu Y, Kohno T, Hirabay-
ashi K: Long-term follow-up studies
of open-door expansive laminoplasty
for cervical stenotic myelopathy. Spine
1994;19:507-510.
25. Emery SE, Heller JG, Petersilge CA,
Bolesta MJ, Whitesides TE Jr: Tibial
stress fracture after a graft has been
obtained from the fibula: A report of
five cases. J Bone Joint Surg Am 1996;
78:1248-1251.
26. Vail TP, Urbaniak JR: Donor-site mor-
bidity with use of vascularized autoge-
nous fibular grafts. J Bone Joint Surg
Am 1996;78:204-211.
27. Martin GJ Jr, Haid RW Jr, MacMillan M,
Rodts GE Jr, Berkman R: Anterior cer-
vical diskectomy with freeze-dried fibu-
la allograft: Overview of 317 cases and
literature review. Spine 1999;24:852-859.
28. Zdeblick TA, Ducker TB: The use of
freeze-dried allograft bone for anterior
cervical fusions. Spine 1991;16:726-729.
29. Macdonald RL, Fehlings MG, Tator
CH, et al: Multilevel anterior cervical
corpectomy and fibular allograft fu-
sion for cervical myelopathy. J Neuro-
surg 1997;86:990-997.
30. Vaccaro AR, Falatyn SP, Scuderi GJ, et

al: Early failure of long segment ante-
rior cervical plate fixation. J Spinal
Disord 1998;11:410-415.
31. Riew KD, Sethi NS, Devney J, Goette
K, Choi K: Complications of buttress
plate stabilization of cervical corpecto-
my. Spine 1999;24:2404-2410.
32. Hosono N, Yonenobu K, Ono K: Neck
and shoulder pain after laminoplasty:
A noticeable complication. Spine
1996;21:1969-1973.
33. Yonenobu K, Fuji T, Ono K, Okada K,
Yamamoto T, Harada N: Choice of
surgical treatment for multisegmental
cervical spondylotic myelopathy.
Spine 1985;10:710-716.
34. Hukuda S, Mochizuki T, Ogata M,
Shichikawa K, Shimomura Y: Opera-
tions for cervical spondylotic mye-
lopathy: A comparison of the results of
anterior and posterior procedures. J
Bone Joint Surg Br 1985;67:609-615.
35. Yonenobu K, Hosono N, Iwasaki M,
Asano M, Ono K: Laminoplasty ver-
sus subtotal corpectomy: A compara-
tive study of results in multisegmental
cervical spondylotic myelopathy.
Spine 1992;17:1281-1284.
36. Riew KD, Hilibrand AS, Palumbo MA,
Bohlman HH: Anterior cervical cor-

pectomy in patients previously man-
aged with a laminectomy: Short-term
complications. J Bone Joint Surg Am
1999;81:950-957.
37. Flynn TB: Neurologic complications
of anterior cervical interbody fusion.
Spine 1982;7:536-539.
38. Emery SE, Smith MD, Bohlman HH:
Upper-airway obstruction after multi-
level cervical corpectomy for myelopa-
thy. J Bone Joint Surg Am 1991;73:544-551.
39. Smith MD, Emery SE, Dudley A,
Murray KJ, Leventhal M: Vertebral
artery injury during anterior decom-
pression of the cervical spine: A retro-
spective review of ten patients. J Bone
Joint Surg Br 1993;75:410-415.
40. Kitchel SH, Eismont FJ, Green BA:
Closed subarachnoid drainage for
management of cerebrospinal fluid
leakage after an operation on the
spine. J Bone Joint Surg Am 1989;71:
984-987.
41. Hilibrand AS, Carlson GD, Palumbo
MA, Jones PK, Bohlman HH: Radicu-
lopathy and myelopathy at segments
adjacent to the site of a previous ante-
rior cervical arthrodesis. J Bone Joint
Surg Am 1999;81:519-528.