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C H A P T E R 2 4 Cervical Stenosis: Radiculopathy – Review of Concepts, Surgical Techniques, and Outcomes
135
toward central posterior disc protrusions. The endplates are cartilaginous
structures situated between the nucleus pulposus and the trabecular bone of
the vertebral bodies. Perforating fibers anchor the endplates to the nucleus
and serve as a conduit for nutrients to enter the disc.
Ligaments and Joints
The cervical spine allows for greater mobility than the thoracic or lumbar
regions. Various ligaments reinforce the cervical spine during flexion, extension, and rotational movement. The anterior and posterior longitudinal
ligaments extend the entire length of the spine and provide stability to the
intervertebral joints. The anterior longitudinal ligament attaches to the ventral aspect of the vertebral column and is apposed to the intervertebral discs,
while the posterior longitudinal ligament courses along the dorsal aspect
of the vertebral column and merges fibers with the annulus as well as the
adjacent endplates (see Figure 24-1C). The ligamentum flavum attaches to
the anterior surface of each vertebral arch and to the superior edge of each
lamina, and covers each facet joint. Its function is to stabilize the neck during flexion (see Figure 24-1D). Due to its considerable elastic capacity, the
ligamentum flavum can normally stretch during flexion without compromising the integrity of the spinal canal. Additional ligaments such as the
supraspinous and interspinous ligaments serve see further stabilize the spinal column (see Figure 24-1B).
The superior and inferior facets comprise the articular pillars (see Figure
24-1A). In the cervix, these joints are angled obliquely and inferiorly and are
oriented perpendicular to the vertebral bodies. Each superior facet articulates anteriorly to its inferior process, forming synovial joints, each with a
fibrous capsule.
Vascular Supply
The cervical cord’s vascularity is provided primarily by the paired vertebral
arteries, which arise from the subclavian arteries in the thorax and course
superiorly to form the basilar artery at the base of the pons. Branches from
the vertebral arteries form the anterior spinal artery, which courses along the
ventral median fissure of the spinal cord, and is responsible for supplying
the anterior two thirds of the cord. The vertebral arteries also give rise to the
paired, posterior spinal arteries, which travel along the dorsal aspect of the
cord (see Figure 24-1D).8 Cervical medullary arteries branching from the
vertebral arteries create variable anastomoses within the canal and contribute additional vascular supplies.
PATHOPHYSIOLOGY OF CERVICAL SPONDYLOSIS
Cervical spondylosis is a multifaceted degenerative process that can affect
all components of the spine including the intervertebral discs, facet joints,
ligaments, spinal soft tissues, and bony elements. The initial pathological
changes in spondylosis originate in the disc space. The proposed mechanism
of disc degeneration occurs secondary to an alteration in the protein composition of the disc matrix. With aging, the molecular weight of the glycoproteins in the disc decreases along with the chondroitin sulfate content. The
net effect is a change in the osmotic properties of the disc, with decreased
inflow of fluid. Dehydration of the disc leads to loss of height, as well as
loss of expansion capability under axial loading. As the disc progressively
loses the ability to distribute normal loads of pressure, the nucleus pulposus becomes predisposed to fragmentation. Fragmentation of the nucleus
combined with increasing weakness in the annulus with aging can result in
herniation of disc material into the spinal canal (Figure 24-2A).
Loss of disc height not only contributes to disc herniation, but also
results in osteophyte formation. As the annulus bulges under the impaired
function of the damaged disc, the periosteum of the adjacent vertebral bodies undergoes reactive processes. Hyperostosis of the subperiosteal bone
generates a spondylotic ridge or osteophyte, which can impinge on the ventral canal to cause cord compression. Spondylosis also leads to hyperostosis
of the posterior elements. In the dorsolateral spinal column, decreased disc
height causes pathological changes in the facets with destruction of the joints
and resultant hypertrophy. Abnormal mobility of the spine contributes to
osteophyte formation in the neural foramina, leading to peripheral nerve
compression and radiculopathy. As spondylosis progresses, the ligamentum
flavum becomes hypertrophic and loses elasticity. During hyperextension
especially, the ligament tends to buckle inward, contributing additionally to
canal compromise.
10
The mechanism by which spondylosis leads to cord injury is not entirely
understood; the pathophysiology is complicated by the common absence of
symptoms in patients with radiographic evidence of significant disease.11
Spondylosis with disc herniation, osteophyte formation, and ligament
hypertrophy clearly reduces the anterior-posterior diameter of the spinal
canal. As expected, patients with congenitally narrow canals are therefore
more prone to be symptomatic. Studies have suggested that the normal
canal diameter is 17 to 18 mm (C3 -C7) and that a reduction in axial diameter to 11 to 13 mm is more likely to lead to myelopathy.10 Abnormal cervical motion and instability following degenerative changes may exacerbate
cord injury. With neck flexion, the cord may move against the ventral spondylotic ridges causing cord damage. E xtension may lead to cord strangulation between the folded ligamentum flavum posteriorly and osteophytes or
herniated disc material anteriorly (Figure 24-2B).
There is considerable debate as to whether cord injury is due to direct
compression of neural structures or secondary to extrinsic compromise of
vascular supply. The vascular ischemia theory was first proposed in 1954
by Brain.2 Breig noted later that in cervical flexion, mechanical flattening of
the spinal cord occurred, with consequent decreased patency of the anterior
sulcal and transverse arteries.12 Other authors have noted that anterior-posterior compression of the spinal cord in both pathologic and experimental
studies resulted in stretching of the transverse vessels and terminations of
the anterior spinal artery with ischemia of the anterior two thirds of the
8,13,14,15
cord.
during flexion in patients with spondylosis.
Clinically, Allen noted that the cervical spinal cord blanched
16
Human pathologic studies of cervical spondylosis demonstrate that
canal compromise with cord compression results in characteristic histological changes. Ono et al. found that compression of the cord is associated
with extensive destruction of both g ray and white matter, with consequent
demyelinization.17 Interestingly, the areas of the cord most encroached upon
tend to display histopathological evidence of severe infarction. Ogino et al.
demonstrated an association between localized infarction of the gray matter and a d ecrease in the anterior-posterior canal ratio to below 20%.18 As
cord injury secondary to spondylosis progresses, tissue destruction leads to
gliosis, scarring, cystic degeneration, and neuronal cell loss.
In conclusion, the pathophysiology of spondylosis appears to be the result
of several degenerative processes that occur in conjunction. The decrease in
disc height leads to herniation, reactive hyperostosis with osteophyte formation, and hypertrophy of the ligaments. These events, along with abnormal
cervical motion, compromise the cord within the canal. The mechanism of
cord injury is still not well understood but appears to be related to impaired
vascular supply leading to neuronal ischemia. As spondylosis becomes more
severe, pathological changes of the cord become evident: demyelination,
gliosis, cystic degeneration, and neuronal cell loss.
CLINICAL PRESENTATION OF CERVICAL SPONDYLOSIS
Cervical spondylosis can present with a variety of clinical syndromes. Pain
may be localized to the neck or display a radicular pattern. Weakness can
occur as a mixture of upper and lower motor neuron findings. Lower motor
signs generally predominate at the level of the lesion, while upper motor
findings are present at segments below. Atrophy and diminished reflexes
are common in the involved upper extremity. Lower segmental involvement
presents as hyperactive reflexes, increased tone, clonus, or (most commonly)
abnormal gait. Sensory impairment is highly variable, with patchy sensory
loss in both the upper and lower extremities occurring along three neural
pathways. Pain and temperature sense are often affected contralateral to the
lesion, due to spinothalamic tract fibers crossing at levels near their entrance
into the canal. The posterior columns, which convey position and vibration
sense, decussate in the brain stem and therefore are often affected ipsilateral
to the lesion. Spondylosis can also affect the dorsal root as it enters the canal,
resulting in impaired dermatomal sensation.
Myelopathy is a common and severe manifestation of cervical spondy-
5
losis.
Symptoms may be slowly progressive and associated with intermit-
tent periods of remission and exacerbation.20 Clinical presentation generally
136
P A R T I V Surgical Treatment Modalities: Cervical Spine
A
C
FI G U RE 2 4- 2 A, A posterolateral disc herniation is shown in this spondylytic cervical spine segment, causing
compression of the nerve root at the level of the foramen without compromise of the cord itself. When symptomatic, such
lesions are typically associated primarily with radicular complaints. B, Multilevel spondylytic osteophytes combined with
chronic disc herniations contribute to a severely narrowed central canal that can be associated with central hemorrhage
and myelomalacia. Clinical syndromes include central cord syndrome and cervical myelopathy. C, A T2-weighted axial MR
image of a cervical posterolateral disc herniation provides an example of root compression in cervical spondylosis. The cord,
although displaced, is not significantly compressed. D, A T2-weighted sagittal MR image demonstrates multilevel spondylytic changes with disc herniations, ultimately causing significant canal stenosis and spinal cord compression. T2-signal
changes within the parenchyma of the spinal cord demonstrate injury to the substance of the neural elements.
B
D
consists of lower motor neuron involvement at the level of the lesion, with
upper motor neuron signs at segments below. Upper extremity involvement is often unilateral, while that of the lower extremity is bilateral. Lower
motor neuron findings include weakness and atrophy with progressive loss
of dexterity, particularly at the level of the lesion. The lower extremities
may demonstrate spasticity, clonus, hyperreflexia, or abnormal gait, with
a positive Babinski sign. Sensory disturbances are poorly localized, generally affecting the lower extremities and trunk, while rarely involving cervical
20
levels.
Bowel and bladder impairment are rare, but indicate poor prognosis.
Due to the complex symptomatology of cervical degenerative disease, Cran-
dall et al. described five clinical syndromes to aid in clustering various findings.
21
1. Transverse myelopathy: involvement of the corticospinal, spinothalamic, and dorsal column tracts, as described earlier.
2. Principally motor symptoms: corticospinal tract involvement with
minimal sensory deficit.
3. B rown-Séquard syndrome: hemi-cord disease affecting ipsilateral
motor strength, ipsilateral proprioception and vibration s ense, and
contralateral pain and temperature sense. Generally reflects an asymmetric narrowing of the canal.
4. Central cord syndrome: motor and sensory deficit predominant in
the upper extremity.
5. Radiculopathy: direct root compression secondary to a herniated disc
or spondylotic change.22 Patients typically present with sensory disturbances in a radicular pattern, specific motor group weakness, and
decreased specific reflex. With chronic disease, profound weakness
and atrophy may be present.
Among other possible findings is the “numb, clumsy hand.”23 This condition involves a glove-like distribution of primary sensory loss combined
with motor loss. Tandem spinal stenosis simultaneously affects the cervical
and lumbar regions, presenting with a trio of symptoms: neurogenic claudication, gait abnormality, and mixed upper and lower motor neuron signs.24
Vertebral artery insufficiency can present with dizziness and unsteadiness
when the head is rotated.25 Rarely, large osteophytes can cause dysphagia
due to direct compression of the esophagus.
5
It is important to consider other neurological conditions that may
exhibit symptoms mimicking cervical spondylosis. Any mass lesion
within the spinal canal that compresses the cord or nerve roots can manifest with such findings. Extradural, intradural, and osseous tumors of
the spine, as well as infectious processes such as epidural abscesses, can
C H A P T E R 2 4 Cervical Stenosis: Radiculopathy – Review of Concepts, Surgical Techniques, and Outcomes
137
compromise canal inte grity. Fortunately, these conditions c an generally be
distinguished from ce rvical spondylosis via effective MRI. Multiple sclerosis is another condition commonly confused with cervical spondylosis,
and a mixed picture of upper and lowe r motor neuron signs is a hallmark
finding in amyotrophic lateral sclerosis. Correctly diagnosing cervical
spondylosis depends on detailed history-taking, complete neurological
examination, and diagnostic measures including imaging, neurophysiology, and laboratory tests.
DIAGNOSTIC MODALITIES
Neuroradiology
Plain film radiographs of the cervical spine are traditional ly performed with
a series of anteroposterior, lateral, and oblique films. Relevant findings on
lateral films in cl ude the height of disc spaces and evidence of osteophytes
protruding into the spinal canal. Also of import is the anteroposterior
diameter of the canal, as it is highly indicative of disease severity in patients
with symptomatic spondylosis.22 The diameter is determined to be the
shortest distance from the dorsal aspe ct of the vertebral body (including
any posteriorly projecting disc s or spurs) to the spino laminar line, with
12 mm in the lower cervical region being the lowest normal value.26 This
calculation, however, is manipulated by the magnification of the film —
an obstacle circumvented by an alternative method described as Pavlov’s
ratio.27 This number represents the ratio of the anteroposterior diameter
of the spinal canal divided by the anteroposterior dia m eter of the corresponding vertebral body. A normal value is approximately 1, with values of
0.8 or less suggesting compression. This method allows quick appraisal of
the integrity of the canal w ithout being influenced by magnification.
Computed tomography allows for better assessment of the spinal canal
than plain radiography.26 CT axial plane images have been shown to provide an accurate estimate of the canal diameter while also differentiating
laterally projecting osteophytes and midline calcifications (i.e., as seen in
OPLL).28 CT scans alone, however, poorly visualize the soft tissue structures within the spinal canal. With the addition of intrathecal contrast, CT
myelography can allow for quantification of cord compression at every level.
CT myelography has been effective in correlating symptomatic disease with
cross-sectional area of the canal.
Magnetic resonance imaging is the most recent advancement in the
radiographic evaluation of cervical spondylosis, offering the advantages
of imaging in multiple planes and improved definition of neural and ligamentous elements. Disc herniations are readily demonstrated and often
have associated signal changes (see Figure 24-2C). MRI also distinguishes
cervical spondylosis from disease processes that mimic it clinically, such as
tumors, epidural masses, demyelination, and syrinx. The complete neuraxis
can also be easily imaged if necessary. In comparison to CT myelography,
MRI is a safer, less invasive procedure, making MRI the procedure of choice
for initial evaluation of radiculopathy or myelopathy.
Unlike conventional x-ray technology, MRI allows for the demonstration
of pathological processes within the spinal cord parenchyma. Intramedullary signal intensity changes have been noted at segments adjacent to areas of
spondylotic compression32 (see Figure 24-2D). In experimental models, his-
tological confirmation of cord injury is found at levels demonstrating MRI
signal change with maximum mechanical compression.33 The cause of signal
change is attributed to myelomalacia, gliosis, and edema.
correlating the degree of signal change with outcome are confusing at best,
but high-intensity lesions are thought to suggest poor prognosis.
MRI still poses problems in diagnosing certain degenerative changes.
Small, lateral osteophytes can be difficult to distinguish from lateral disc
herniations.28 Also, midline calcifications seen in ossification of the posterior longitudinal ligament (OPLL) may be poorly visualized. In addition to
these limitations, the high incidence of degenerative abnormalities imaged
in asymptomatic individuals also proves problematic. Teresi et al. found disc
protrusions in 57% and spinal cord impingement in 26% of patients over 65
years of age when clinical evidence of cervical spondylosis was absent.39 So
although imaging techniques allow direct visualization of disease progression, determination of patient prognosis and indication for surgical intervention is not made by such modalities alone.
29
28,30,31
32,34,35
Clinical data
34,36,37,38
Neurophysiology
Neurophysiological evaluation of cervical spondylosis may prove a valuable
supplement to other findings. Recent interest in these functional diagnostic
modalities stems from the difficulty in interpreting common radiographic
abnormalities in asymptomatic patients. Neurophysiological testing may also
assist in predicting prognosis and measuring response to treatment. In evaluating cervical spondylosis, electromyography (EMG) allows differentiation
of radiculopathy from neuropathy, and peripheral from central nerve entrap-
40
ment.
EMG also helps localize affected nerve roots by demonstrating conduction abnormalities in muscles innervated by adjacent cervical segments.
This technique may assist in preoperative determination of levels requiring
decompression. Somatosensory evoked potentials (SSEPs) involve electrical
stimulation of peripheral sensory nerves while recording evoked activity from
either the spinal cord or sensory cortex. Clinical studies showing spondylotic
involvement of the posterior columns suggest that SSEPs may help appraise the
functional status of the sensory system. Leblhuber et al. found that dermatomal
SSEPs were altered at levels corresponding to cervical segments with degenerative changes.44 Yet these neurophysiologic and radiographic abnormalities
were also found in asymptomatic patients. Although experimental models have
found a temporal relationship between changes in SSEPs and the onset of neurological deficit,33 the diagnostic value of SSEPs has been challenged through
studies that found median and ulnar nerve abnormalities in only a small percentage of patients with symptomatic cervical spondylotic myelopathy.
42,43
Cortical motor evoked potential (MEP) recording has been suggested
as a more sensitive test of spinal cord dysfunction than SSEPs,44 due to
the predominance of motor findings in patients with cervical spondylosis.44
MEP abnormalities may also be detected in patients before the onset of
clinical symptoms.
84% of patients with radiographic cord compression, while SSEPs show
dysfunction in only 25%.
43-45
In comparison, MEP can detect abnormalities in
46
The role of electrophysiological studies in diagnosing cervical spondylosis or predicting outcome is not entirely clear at this time. Cusick suggests
that combining MEP and SSEP recordings allows for evaluation of long
tract function of both ascending and descending white matter. These two
tests provide insight into the integrity of two spinal cord areas often affected
by spondylosis. By integrating electrophysiological studies and radiographs,
patient vulnerability to neurological deficit may be estimated, as well as optimal timing of surgical intervention for patients with subclinical disease.
44
NATURAL HISTORY OF CERVICAL RADICULOPATHY
The natural history of cervical spondylosis is not well described. Since early
descriptions of the condition, surgery was widely accepted as the treatment
of choice, and no studies were made to determine long-term progression.
Only a few investigators have attempted to formulate a likely picture using
patients treated with a collar.
Lees and Aldren-Turner classified cervical spondylosis as a relatively
benign condition.19 The common course experienced by their patients was
characterized by long periods of stable symptomatology interspersed with
short bouts of deterioration; chronic, gradual deterioration was rare. They
also found that myelopathy did not develop in a group of patients presenting solely with radiculopathy. In following studies, Nurick agreed with the
findings of Lees and Aldren-Turner, and also found that patients who had
undergone surgical laminectomy had no significant improvement over those
with no treatment.3 Thirdly, he realized that age of onset served to significantly determine the prognosis for later deterioration.
When comparing 48 patients who underwent surgery with those in Lees
and Aldren-Turner’s study, the other authors found that 70% of patients
enjoyed improved conditions from cervical laminectomy. Their conclusion
was that patients with moderate or severe symptoms due to cervical spondylosis benefit greatly from surgery, whereas those with mild disability are not
likely to be significantly helped. Doubt was later cast upon Lees and AldrenTurner’s theories in that they were thought to have bias toward milder cases.
Scoville found that the best outcome of surgery was in patients treated
within one year of onset of symptoms.48 He further elaborated on Lees and
Aldren-Turner’s model in claiming that patients should be treated surgically,
shortly after mild disability was noticed, and before further progression. He
did admit that mild cases were adequately treated conservatively.
138
P A R T I V Surgical Treatment Modalities: Cervical Spine
Smith and Robinson more recently described the course of cervical spondylosis that is most accepted today.47 They found that motor complaints
tended to be more permanent than neck, bladder, and sensory symptoms.
Motor findings were also predominant in the lower extremities, and sensory in the upper. Although most of their patients followed an episodic but
unpredictable pathway, one third of cases were found to be nonprogressive
between acute episo d es, while two thirds experienced a gradual increase in
symptoms between intermittent, acute episodes of worsening. A minority of
patients had a constant worsening in condition, and very few people enjoyed
spontaneous improvement. Their conclusion was that although progression
of the disease is usually slow, prognosis is poor, and improvement rare. They
hypothesized that patients reporting improvement may simply be coping
better, or may simply be reporting a slowing of progression.
Although many agree that there is a need to compare the outcome of different surgical treatments for cer vical spondylosis with the natural history,
such a study would be unethical. As surgery is widely accepted as incontrovertibly beneficial, it would prove difficult to randomize patients with severe
or progressive disability to nontreatment.
TREATMENT AND DECISION-MAKING
Two options exist for treating cervical spondylosis: conservative and surgical. Conservative treatment is aimed toward patients with milder symptoms
and can range from simply monitoring the patient to isolating the neck
with a hard or soft collar. The collar should hold the neck either neutral or
slightly flexed, with duration of use varying between patients. Drug therapy
is another option in nonsurgical treatment, consisting of analgesics, muscle
relaxants, and nonsteroidal antiinflammatory drugs. Analgesics are used to
relieve acute pain episodes, and muscle relaxants to reduce muscle spasm
(which can lead to pain and ischemia) and increase range of motion. The
goal of antiinflammatory therapy is to reduce impingement upon nerve
roots due to inflammation. It should be noted that drug therapy is recommended as a supplement to immobilization; rest is the best conservative way
to reduce symptoms.
Surgical intervention is used when patients suffer moderate, severe, or
progressive disability. A defi nite diagnosis must be made before surgery is
used to reduce narrowing of the canal and stabilize the vertebral column.
POSTERIOR CERVICAL SURGICAL TECHNIQUES
Cervical laminoforaminotomy and laminectomy is the classic posterior
approach used in treating cervical spondylosis, and is still used in patients
suffering posterior canal compression from a hypertrophic ligamentum
flavum. In this procedure, the lamina is removed from the affected level and
those adjacent to it; foraminotomies may also be performed to relieve radiculopathy. This surgery is contraindicated in patients lacking normal cervical
curvature or suffering f rom cervical instability. In the latter case, laminectomy may be performed if preceded by anterior cervical fusion.
Laminoforaminotomy and laminectomy should be performed under
general anesthesia, with the neck in a neutral position to prevent stretching of the spinal cord over any anterior protrusions within the canal. The
patient can either sit or lie prone; the former allows a dry field, but increases
the risk of an air embolism. After proper fixation of the head in pins and/or
traction as noted above, radiographic assessment of the spinal alignment and
confirmation of the neurological exam should b e obtained prior to incision
(Figure 24-3A). A midline incision is then made over the pathology in question. For occipitocervical fusions, this incision should typically extend from
the inion on the skull to slightly above the C7 prominence. A more limited
F IG UR E 24 -3 A, For posterior approaches, the patient
is typically positioned prone, either on a horseshoe or in surgical
Mayfield pins as shown here. The arms are typically tucked downward to maximize surgical exposure. B-C, Dorsal midline exposure
of the posterior cervical musculature with section of the interspinous ligaments reveals the underlying dorsal bony arches with the
lamina and spinous processes. Wider dissection exposes the pillars
of the articular facets with their bodies and the articular capsules
encasing the joint spaces themselves.
Traction
A
B
16
9
19
20
17
18
C
C H A P T E R 2 4 Cervical Stenosis: Radiculopathy – Review of Concepts, Surgical Techniques, and Outcomes
139
incision can be made for subaxial cases. Due to the narrowed interspaces and
inferior inclination of the spinous processes, overdissection and stripping of
the facets may lead to unwarranted fusion of uninvolved levels, leading to an
excessive decrease in mobility.
The dissection is carried down sharply in the midline to the level of the
posterior cervical musculature fascia. A midline raphe is formed from the
union of the deep cervical fascia, prevertebral fascia, ligamentum nuchae,
and the supraspinous ligaments (Figure 24-3B). By maintaining the exposure in this relatively avascular midline plane, blood loss can be minimized. Frequent palpation of the bony processes demarcat ing the midline
is essential. Self-retaining retractors are placed to maintain the exposure,
but excessive retraction can obs cure the midline and lead to scything to
either side.
After the ligamentum nuchae is encountered over the cervical spinous
processes, a subperiosteal dissection is performed to mobilize the muscles
off the processes. As the processes are often bifid, care should be taken to
avoid accidental spinal canal entry. The exposure is then carried down to
the lamina which are palpated and identified. Using gentle lateral retraction
with a small Cobb elevator, electrocautery is used to dissect the muscles off
the lamina (Figure 24-3C). Excessive downward pressure with the elevator
must be avoided, as the cervical spine is highly mobile even in its normal
state under anesthesia. The laminae of the cervical spine are angulated 45
degrees from medial to lateral and also in a cephalic direction. The interlaminar areas are also wide and should be exposed cautiously. It is here that the
venous plexus overlying the vertebral artery is often encountered as the facet
capsule is exposed. Bipolar cautery and gentle tamponade with Gelfoam are
usually effective in obtaining hemostasis. For uninvolved levels, care should
be taken to preserve the facet capsule (zygapophyseal joint). Self-retaining
retractors to maintain exposure should be placed at or above the anteroposterior plane of the facets to avoid injury to the nerve roots and vertebral
artery.
Alternatively, a minimally invasive paramedian tubular approach can
be used as well. A stab incision is initially made approximately 1 cm off
midline ipsilateral to and at the level of the pathology. Under fluoroscopic
guidance, a small tubular dilator or pin is inserted through the posterior cervical musculature and fascia dow n to the facet or lateral mass of the target
level. Although we have not routinely done so, anteroposterior radiographic
images could be obtained to guarantee proper pin positioning (Figure
24-4A). Once the dilator has been docked on the facet in question, the skin
incision is extended above and below the Steinmann pin for a total length of
approximately 2.0 cm. The skin edges are retracted and the cervical fascia is
incised using Metzenbaum scissors. Care should be taken not to cut muscle
fibers during this procedure, as this can cause unnecessary blood loss. This
sharp opening of the fascia allows for easier passage of the sequential dilating cannulas with a minimum of force (Figure 24-4B). A series of dilators
is then sequentially inserted through the neck soft tissues, over which an
18mm tubular retractor is then inserted (Figure 24-4C). Real-time lateral
radiographic images are obtained as often as needed to insure a proper
working trajectory throughout this process (Figure 24-4A-C). The working
channel (tubular retractor) is then attached to a flexible retractor affixed to
the operating table side rail, and locked in position at the junction of the
lamina and lateral mass (Figure 24-4D).
Once the standard or minimally i nvasive retractor is se t in the desired
position over the correct level as confirmed by fluoroscopic imaging, a Bovie
cautery with a long tip is then used to remove the remaining muscle and
soft tissue overlying the lateral mass and facet. Typically loupe magnification or an operating microscope is used for maximal visualization. With the
bone well delineated, a small straight cervical curette is used to scrape the
inferior edge of the superior lamina and the medial edge of the lateral mass/
facet. This exposure is then carried underneath the lamina and facet with
the use of a small angled curette. Proper placement of the curettes can be
confirmed under fluoroscopy. Good dissection of the underlying flavum and
dura from the bone defines the relevant anatomy and helps to prevent incidental dural tears. Bleeding from epidural veins and the edge of the flavum is
controlled via long-tipped bipolar cautery. A small angled Kerrison rongeur
is then utiliz ed to begin the foraminotomy. Periosteal and bone bleeding is
addressed with bone wax and cautery. In cases of marked facet arthropathy and enlargement, a dril l with a matchstick-type bit is used to further
thin the medial facet and lateral mass (Figure 24-5A,B). Dissection with an
angled curette facilitates safe use of the Kerrison rongeur. In this fashion, the
decompression is continued.
The laminoforaminotomy is completed when the nerve root has been
well exposed along its proximal foraminal course. The adequacy of the
decompression should be confirmed by palpating the root along its course
with a small nerve hook (Figure 24-5C). In cases in which a herniated disc
was present, either a nerve hook or small #4 Penfield elevator is used to
mobilize the nerve root superiorly to expose the disc space and fragment.
For this maneuver, additional exposure is obtained by drilling a small portion of the superomedial portion of the pedicle directly below the exiting
nerve root. With the root retracted, the disc f rag ment is then removed in
a standard fashion with c urettes and long endoscopic pituitary rongeurs
(Figure 24-5D). Additional osteophytes encountered in this region can also
be drilled or curetted as needed. Upon completion of the discectomy and
decompression, the nerve hook is again passed along the exiting root to confirm its free passage and a lateral fluoroscopic image is obtained.
After inspection of the nerve root, hemostasis is obtained by bipolar
cautery and gentle tamponade with thrombin-s oaked Gelfoa m pledgets.
The area is then copiously irrigated with lactated Ringer’s solution impregnated with bacitracin. A small piece of Gelfoam soaked with Solu-Medrol
is gently placed over the laminoforaminotomy defect. A soft collar can be
fitted for patient comfort, but is not necessary, as early mobilization is recommended. Major complications consist of wound healing and infection.
ANTERIOR CERVICAL SURGICAL TECHNIQUES
Another surgical option i s the anterior approach, which allows for fusion
of the vertebral column concurrent with removal of osteophytes and prolapsed discs protruding into the anterior space of the canal. This approach
A
C
F IG UR E 2 4 -4 A-D, Lateral intraoperative fluoroscopic images dem-
onstrate sequential tubular dilation of the dorsal musculoligamentous complex
with ultimate docking of a working portal at the level of the C5/6 posterior
laminofacet junction and disc level.
B
D
140
P A R T I V Surgical Treatment Modalities: Cervical Spine
A
C
FI G U RE 24 - 5 A-D, After exposure and confirmation under fluoroscopy, a high-speed drill burr is used to decom-
press the laminofacet junction. The lateral aspect of the cord and the exiting nerve root are exposed (A). Immediately invest-
ing these structures is the epidural venous complex, which often requires hemostasis via tamponade and bipolar cautery
(B). The decompression is confirmed with the use of a nerve hook or probe to palpate the course of the exiting nerve root
(C). For cases where fragmentectomy is required, a small retractor is used to elevate the nerve root to gain access to the
disc space (D).
is preferred in cases involving compression at one or two levels (although it
is rarely performed in cases with three or four), and is particularly useful for
patients with cervical instability. Several variations upon this method have
arisen since its inception, with none having a distinct advantage.
As with laminectomy, this procedure is performed under general anesthesia, with the neck in a neutral position. The patient is placed in supine
position with a roll placed transversely between the scapulae in order to
extend the neck (Figure 24-6A). Following palpation of landmarks, a 2
to 3 cm skin incision is made along a skin crease at the level of interest betwee n the sternocleidomastoid (SCM) and slightly off the midline
(M) (Figure 24-6B). Finally, ensuring the correct level of the skin incision
also prevents difficulty in dissection. Palpable landmarks in the neck aid
in identifying the approximate level. The inferior angle of the mandible
corresponds to C2-3; the hyoid bone to C3; thyroid cartilage to C4-5;
the cricoid cartilage to C6, and the carotid tubercle to C7. Alternatively, a
longer oblique or longitudinal incision can be made if an extensive decompression is planned (i.e., greater than 3-level corpectomy). Injection of
lidocaine with epinephrine into the skin prior to incising may help diminish superficial bleeding.
Incise the superficial fascia overlying the platysma along the skin incision. The subsequent surgical course is through a potential space through
the trajectory demonstrated in Figure 24-6C. The fibers of the platysma
muscle are then either incised longitudinally along the direction of its fibers
or split transversely. The deep cervical fascia underneath is then identified.
Next, palpate the medial border of the sternocleidomastoid muscle and
carefully split the fascia longitudinally. This allows one to retract the SCM
laterally. The laryngeal strap muscles (sternohyoid, sternothyroid) as well as
the midline structures immediately deep to them (trachea [T ] and esophagus [E]) are then retracted medially. Deep to the SCM muscle, identify the
carotid sheath (C) as well as the pretracheal fascia overlying it. Carefully
incise the fascia medial to the sheath while protecting the midline structures.
The carotid sheath can now also be retracted laterally.
B
D
Using blunt dissection, develop a plane toward the midli ne until the
prevertebral f ascia directly anterior to the vertebral bodies can be visualized. Identify the midline of the vertebral bodies (corresponding to the
white stripe of the anterior longitudinal ligament) as well as the longus
colli on each side. Using electrocautery, incise the prevertebral fascia longitudinally to the desired length. Use a periosteal elevator to then subperi osteally uncover the vertebral bodi es and intervening disc spaces (A). Place
retractors under each longus colli muscle to protect surrounding structures. The view of the field is provided by an operative microscope, which
minimi zes risk of injury during cord decompression. Place a spinal needle
in a disc sp ace and o btain a cross-ta ble lateral film of the cervical spine to
confirm the level. An assistant pulling axially on wrist straps depresses the
shoulders a nd allows for a better radiograph. After conf irming the level,
a discectomy and/or corpectomy can be performed as indicated. Distraction pins can be placed in the appropriate vertebral bodies, and general
distraction appli ed to facilitate discectomy and decompression, particularly in heavily collapsed spaces (Figure 24-7A).
The prolapsed disc and osteophytes are removed, and a bone graft is
inserted within the interspace to provide stability and promote fusion.
Typically, straight and angled curettes are used to free the disc and cartilaginous portions of the endplate from the bony vertebral body surfaces. Fragments of disc are then removed with pituitary rongeurs (Figure 24-7B).
This process is gradually advanced down toward the level of the posterior
longitudinal ligament (PLL). At times, drilling with a matchstick-type
high-speed drill bit is useful to flatten irregular endplate osteophytes as
well as to remove anterior closing lip osteophytes. Particular attention,
however, should be taken to avoid excessive damage to the bony endplates,
especially if grafting will be done, to prevent excessive subsidence of the
graft. The PLL is then opened sharply w ith a sma ll 1- or 2- mm Kerrison
rongeur. Initial opening can be facilitated with the use of a small nerve
hook probe. The PLL is then sectioned to reveal the underlying dura a s
needed, depending on the exact extent and location of the neurological
C H A P T E R 2 4 Cervical Stenosis: Radiculopathy – Review of Concepts, Surgical Techniques, and Outcomes
M
141
A
A
E
ML
C
FI G U RE 24 -6 A-C, For anterior cervical approaches, the patient is positioned supine, often with either a chin strap
or traction tongs to optimize the exposure and the cervical lordosis. The C-arm can be draped in as well (A). The incision is
marked at the level of the pathology, based on either anatomic landmarks or fluoroscopic guidance between the sternocleidomastoid [SCM] and the midline [M] (B). The surgical course is a lateral-to-medial type of trajectory passing through
the skin, platysma, and the external cervical fascia (C). Once opened, this potential viscerocarotid space is split between the
carotid sheath [C] laterally and the trachea [T] and esophagus [E] medially. The retractors are ultimately secured at the level
of the prevertebral space at the anterior border of the spine (A).
compression as determined by the preoperative imaging and the patient’s
clinical symptoms. It is particularly important to extend the decompression
rostrocaudally by undercutting the marginal endplate osteophytes in an
hourglass shape to ensure that there is no residual canal or foraminal compression (Figure 24-8A). The majority of surgeons, therefore, choose to
remove larger osteophytes from posterior and posterolateral canal sur faces.
Some surgeons also choose to open and excise the posterior longitudinal
ligament. Doin g so allows prolapsed discs to be more easily identified for
removal (which is useful in up to 35% of cases). Further, excision of the
ligament provides prophylaxis against buckling, a possible source of postoperative pain.
Autologous bone grafts are usually taken from the iliac crest (over
70% of the time), with other options including the patient’s tibia or fibula,
bone ban ks, and calf bone (Figure 24-8B). A rtificial grafts are also possible using methylmethacrylate, hydroxyapatite, or biopolymer. Although
such materi als do not necessarily provide a better outcome, donor site
pain can be eliminated. Benefits of fusion include reduced risk of repeated
spinal cord injury and pain by mi nimizing abnormal movement, as well
as prevention and treatment of residual or recurrent nerve root compression via loss of disc space height. Another advantage of fusion is increased
resorption of osteophytes, although complete resorption may t ake several years. A variety of specific interbody grafting techniques including
T
B
C
Surgical course
SCM
ML
SL
SCM
O
the Smith-Robinson impacted type, the Cloward dowel, and the BaileyBadgely slot type grafts have bee n commonly employed over the year s
(Figure 24-8C).
The necessity of grafts is questioned, however, in that fusion occurs in
over 75% of patients who do not receive a graft. The first reported anterior
cervical decompression surgery without fusion was in 1960. In this procedure, the dis c is resected to achieve decompression, and the space is left
empty. The nonfusion anterior approach is used in patients suffering acute
soft disc prolapse with minimal osteophyte formation, and neurological outcome is outstanding. Patients tend to have shorter recovery time with fewer
complications. When osteophytes must be removed, the outcome is generally not as good as with fusion; many patients suffer new or recurrent pain
symptoms. As such, the majority of modern surgeries now employ grafting
with or without plating.
Vertebrectomy with strut grafting is a more recent surgical tool used
in treating patients suffering from severe disease at many levels. Significant
improvement is reported in 70% to 80% of cases, and many authors feel
that this procedure is superior to other surgical options. When performing
vertebrectomy, a trench is drilled out along the axes of the affected vertebra
and disc spaces to achieve decompression, and the column is reconstructed
using a graft from the iliac crest, rib, or fibula. In cases requiring immediate stabilization, titanium or PEEK implants can be used to reinforce the
142
P A R T I V Surgical Treatment Modalities: Cervical Spine
C7
T2
A
FI G U RE 2 4 -7 A-B, After developing flaps under the longus colli laterally, the retractor blades are then secured
underneath them to provide exposure to the spine. If desired, Caspar-type distraction pins can be secured into the surrounding vertebral bodies (A). Annulotomies are then made with a scalpel blade and discectomy completed with a combination of angled curettes, drill, and Kerrison and pituitary rongeurs (B).
vertebral column, while also providing magnetic resonance imaging compatibility for postoperative imaging.
Anterior cervical microforaminotomy is a well-established minimallyinvasive anterior cervical procedure and has the advantage of good decompression of the nerve root and maintenance of spinal stability without the
need for fusion.. Technically more demanding, decompression of the nerve
root is achieved by removing the osteophytes from a lateral to medial trajectory with a focus on preserving the structural stability of the remaining joint
and intervertebral disc (Figure 24-9A,B). Small slim retractors are docked at
the junction of the lateral uncinate joint and the transverse process, immediately medial to the vertebral artery at the level of the disc and exiting nerve
root (Figure 24-9C). With the vertebral artery retracted laterally, curettes
and drill bits are used to expand the foramen and decompress the lateral
aspect of the uncinate joint through the dorsolateral osteophyte (Figure
24-9D). Once exposed, the disc herniation is resected with micropituitary
forceps (Figure 24-9E) to thereby ultimately decompress the neural foramen and exiting root (Figure 24-9F).
SURGICAL OUTCOMES
Assessing the results of surgery for cervical spondylosis has proved difficult
for many reasons. As the disease is heterogeneous in presentation, studies
include a variety of cases disparate in age, extent of vertebral involvement,
and severity of symptoms. To date, no prospective, randomized experiments
have been published. Currently available publications consist mostly of retrospective reviews of different procedures performed at the same institution.
Furthermore, there is no standardized method of assessment. The Japanese
Orthopedic Association proposed a scale involving four-limb function and
bladder symptoms. The Odum scale grades from excellent to poor, and the
Nurick system assesses ability to walk. Magnetic resonance has been used to
determine the underlying cause of poor postoperative results. In examining
56 patients, Clifton found that only 12 patients had adequate decompression at the correct levels, whereas 32 cases had either residual compression
at operated levels or untreated compression at additional levels.55 Batzdorf
B
and Flannigan similarly found patients with residual cord compression.
Harada found that when significant decompression was not achieved,
recovery was significantly worse.57 In light of these findings, the necessity of
preoperative imaging for accurate determination of involved levels and best
method of approach becomes apparent.
The effectiveness of posterior cervical laminoforaminotomy for decompression of the lateral recess and neural foramen has been well documented
in numerous publications over the last four decades.
to standard anterior cervical techniques, the posterior approach via a “keyhole” type of osteotomy may provide better exposure for decompression of
the exiting root and for removal of lateral osteophytes and discs. Previous
work examining laminoforaminotomy has shown that adequate foraminal
exposure can be accomplished without necessarily destroying the facet joint
or causing iatrogenic instability.50 As long as less than 50% of the facets are
removed, there is little compromise of the sheer biomechanical strength of
the cervical spine.51 The posterior approach also avoids the additional risks
of injury to the anterior structures of the neck including the trachea, esophagus, thyroid, thymus, carotid arteries, jugular veins, vagus nerve, recurrent
laryngeal nerve, superior laryngeal nerve, ansa cervicalis, and thoracic duct.
Lastly, cervical laminoforaminotomy is an operation that treats the offending pathology without necessitating a fusion. As longitudinal studies now
demonstrate an increased incidence of adjacent level problems following
cervical fusion, avoiding arthrodesis when possible seems particularly pru-
52
dent.
Overall, no statistically-significant difference in results between
anterior and posterior approaches for the management of isolated cervical
radiculopathy has been demonstrated.53 The overall clinical popularity of
laminoforaminotomy was tempered by technical limitations including a limited surgical view, difficulty in resecting osteophytes, limited visualization of
the distal foramen, and often generous epidural venous plexi and associated
bleeding.54 Furthermore, the muscle dissection often needed to obtain an
adequate surgical exposure has been associated with increased postoperative
muscle spasm, neck pain, and recovery time. When considering laminectomy, reported results tend to disagree. With respect to age, some investigators find a significantly better outcome in patients under 50, while others do
48, 49
When compared
56
FT
C H A P T E R 2 4 Cervical Stenosis: Radiculopathy – Review of Concepts, Surgical Techniques, and Outcomes
143
A
B
M
Smith-Robinson
Cloward
Bailey-Badgely
C
F IG UR E 2 4 -8 A-C, Typically a funnel or hourglass-shaped decompression is carried through the disc space to avoid inadvertent injury to the vertebral arter-
ies, which are lateral at the level of the midbody (A). Widening of the exposure at the level of the canal and foramen is essential to ensure adequate decompression
of the neural elements. Once the discectomy is completed, most surgeons opt to place an interbody graft comprised of either autograft bone, allograft bone, or
synthetic material (B). A variety of specific interbody grafting techniques including the Smith-Robinson impacted type, the Cloward dowel, and the Bailey-Badgely
slot type grafts have been commonly employed over the years (C).
not. Regarding general overall improvement, some studies reported benefit
in over 80% of cases, whereas others found no significant advantage over
conservative therapy. Finally, most authors agree that shorter duration of
preoperative symptoms is a good prognostic factor, while some deny any
significance. Possible confounding factors include the consideration of cases
where osteophyte removal, opening of the dura, or sectioning of the dentate
ligaments was performed concurrently with laminectomy (which tends to
cause more complications due to neural injury). Despite the glaring differences, it is generally believed that younger patients who have less neurological involvement and a shorter duration of disease enjoy greater improvement.
Overall, clinical outcomes associated with the surgical treatment of
degenerative disc disease by anterior cervical discectomy (ACD) or anterior
cervical discectomy and fusion (ACDF) have been excellent. According to a
literature review from 1991,58 good clinical outcomes have been reported for
61% to 94% of ACDF cases and for 65% to 96% of ACD cases. These data
showed that an interspace fusion is not mandatory for good clinical outcomes.
The development of a fibrous union or pseudarthrosis has not been consistently associated with poor clinical outcomes. However, once pseudarthrosis is present, 67% of patients have associated symptoms.59 Since then, the
question of whether an interbody fusion is required has been unresolved.60
Proponents of ACD favor its simplicity, low cost, and the absence of complications related to autograft harvest and interbody graft failure (e.g., graft
extrusion, collapse, subsidence, and pseudarthrosis). Advocates of ACDF
stress that foraminal decompression by interbody distraction, prevention of
disc space collapse, and stabilization of cervical alignment are key advantages
compared with ACD alone. The resorption of dorsal osteophytes has been
attributed to fusion and immobilization of the segment. The postoperative
incidence of neck pain has been reported to be smaller with fusion than
without. Furthermore, the incidence of kyphotic deformity is thought to be
higher if fusion is omitted. Comparative, prospective clinical studies between
ACD and ACDF, however, failed to find a clinical benefit to ACDF.
61-68
Despite these findings, the overall trend in the United States and Canada has been toward increased application of anterior interbody fusion for
the treatment of cervical degenerative disc disease.
69-71
Autograft from the
iliac crest has usually been used for interbody fusion. However, its harvesting is associated with complications such as prolonged pain, cosmetic deformity, wound infection, hematomas, and peripheral nerve irritation or injury.
Unplated anterior cervical interbody fusion for degenerative disc disease
has a higher tendency to fuse with autograft than allograft, sometimes with
better clinical outcomes.
significant differences in radiological or clinical outcomes between allograft
and autograft.
75-77
72-74
In contrast, other studies failed to demonstrate
A meta-analysis of the literature comparing fusion outcomes of allograft and autograft for one- and two-level cervical interbody
fusion without plating found a higher fusion rate for autograft and a lower
144
P A R T I V Surgical Treatment Modalities: Cervical Spine
Vertebral artery
Compressed
nerve root
Medial Lateral
Herniated disc
and osteophyte
A
F IG UR E 2 4 -9 A-F, Anterior cervical microforami-
notomy is a slightly more lateral approach than used in
standard anterior midline cervical disectomy, and instead
focuses on the lateral aspect of the disc space at the level
of the neural foramen immediately medial to the vertebral artery (A, B). Once exposure is obtained with slimblade type retractors between the uncinate joint and the
vertebral artery laterally (C), curettes and drills are used
to complete the bony decompression and foraminotomy
(D). The herniated fragment is exposed and resected with
micropituitary forceps (E) to ultimately complete a good
decompression of the neural elements (F).
B
incidence of graft collapse than for allograft. However, clinical outcomes
were statistically similar.78 A review of the literature failed to find allograft
to be an adequate equivalent to autograft for anterior cervical interbody
fusion.79 However, the morbidity associated with autograft harvest was
eliminated by the application of allograft. The possibility of transmitting
infectious diseases like human immunodeficiency virus from tissues, including allograft, donated by a screened donor is exceptionally rare.
75, 76
A prospective study of ACDF comparing autograft and biocompatible
osteoconductive polymers found significantly less graft protrusion and intersegmental kyphosis in the biocompatible osteoconductive polymer group.
However, this study failed to demonstrate incorporation or biodegradation
of biocompatible osteoconductive polymers.80 In a prospective, nonrandomized study, Senter et al. 81 compared the outcomes of autograft ACDF with
ACDF with hydroxyapatite. Fusion with the latter was equal or superior to
that with autograft alone. In prospective comparisons of autograft and xenograft, clinical and radiological data favored the use of autograft.
82,83
Recent prospective clinical trials of fusion with interbody titanium cages
have found promising clinical results and radiological outcomes, with low
rates of implant failure (e.g., backout and subsidence) or pseudarthrosis
when compared with allograft or autograft. Even the fusion rates for cages
are superior to those associated with autograft or allograft fusion.
Despite these recent data, some conclude that autograft remains superior to
alternative interbody fusion materials.
87
84-86
In the early 1960s, Bohler88 applied an anterior cervical plate and screw
construct to treat traumatic instability of the spine. After his report, anterior
cervical plate constructs were applied using bicortical, nonlocked, variableangle screws for fixation.
89,90
However, hardware failure was common,91
and a unilateral locked, fixed-angle plate-screw anterior system was introduced by Morscher et al.92 in 1986 (Figure 24-10A).
A variety of unicortical locked, dynamic, fixed, or hybrid plate-screw systems are now available for anterior cervical interbody fusion and plating93 to
increase stability of the cervical fusion segment (Figure 24-10B,C). As a result,
fusion rates have increased, and the rates of graft failure and pseudarthrosis
C
E
have thereby decreased.
94,95
Furthermore, anterior cervical plate fixation
D
F
for degenerative disc disease maintains sagittal balance more effectively,
thereby potentially limiting adjacent level biomechanical stress.99 Postoperative loss of lordosis and cervical kyphosis have been associated with ACD and
ACDF without plating. Yet, again, prospective randomized studies comparing
single-level ACD, ACDF, and ACDF with plating have failed to show a clinical benefit associated with either procedure,
was found for two-level procedures.
66,100
101
Moreover, concern has been expressed
although a clinical benefit
about the cost and complication of cervical plating for the treatment of degenerative disc disease. Hardware failure has been a source of early and delayed
morbidity. In a prospective clinical trial, patients undergoing ACDF with plating tended to have a more frequent incidence of dysphagia than patients without plating. Yet, in the same study, more multilevel procedures were performed
in the plating group, which could also account for these findings.
In more recent surgical series, refinements in the design of anterior
cervical plating and more surgical experience have lowered the incidence
of plate-related complications.
sible reoperation and time to return to work, are considered, overall costs
decrease when anterior cervical plating is added to fusion.
may increase fusion rates with allograft and thereby obviate the need for
autograft.
111
The complications associated with autograft harvest would be
103-109
When all aspects, including pos-
110
Plating also
decreased without compromising fusion rates. Again, experts are divided on
the need for plating, in particular, for single-level disease.
COMPLICATIONS OF SURGERY
The complications of these procedures are similar to those of any other type
of surgery, with a mortality rate of less than 1.5%. Cardiac disorders, thrombophlebitis (with possible pulmonary embolism), and in fection top the
list. Vessels exposed to injury are the vertebral arteries, the carotid arteries,
and the jugular vein; extradural or superficial hematomas may also occur.
Nerves at risk include the paravertebral sympathetic chains, the superficial and recurrent laryngeal nerves, along with the spinal cord and nerve
102
96-98