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Many options exist for the treatment of degenerative cervical disease,
depending on the symptoms, compressive pathoanatomy, deformity, and
other anatomic considerations. It is important to customize the treatment plan
for each patient’s situation. Different surgical techniques have relative
advantages and disadvantages in the treatment of degenerative cervical
disorders.
Intraoperative and Perioperative Considerations
In addition to the surgical technique, several perioperative factors can
influence patient outcomes. In patients with severe myelopathy, awake
fiberoptic intubation should be considered. The patient should be positioned
without excessive neck extension and postpositioning motor-evoked
potentials should be considered to minimize positioning-related
complications. In addition, the anesthesia team should ensure adequate spinal
cord perfusion by maintaining mean arterial pressure higher than 85 mm Hg.
Intraoperative neuromonitoring of somatosensory-evoked and motor-evoked
potentials is helpful in avoiding intraoperative spinal cord injuries that can
occur during distraction and instrumentation of the cervical spine.
Anterior Surgery: Cervical Fusion and Cervical Disk Arthroplasty
Anterior decompression is the cervical spine procedure most commonly
performed for the treatment of degenerative cervical radiculopathy and
myelopathy. Anterior decompression provides a relatively safe, simple
anatomic approach to the cervical spine and has a high likelihood of relieving
radicular complaints and preventing myelopathic symptom progression.
Currently, two primary variations exist for anterior surgery: the more
traditional anterior cervical diskectomy and fusion (ACDF) and the newer,
motion-sparing option of anterior cervical total disk arthroplasty (TDA).
A Cochrane review compared outcomes of ACDF versus TDA for singlelevel radiculopathy, myelopathy, or both and found statistically but not
clinically significant differences in favor of TDA.9 The review analyzed data
from nine randomized controlled trials with follow-up intervals of up to 2
years. Arthroplasty resulted in a significant reduction in both arm and neck
pain according to visual analog scale (VAS) scores and improvements in both
neck function (Neck Disability Index [NDI]) and global function (Medical
Outcomes Study 36-Item Short Form [SF-36]). However, despite these
statistically significant differences, no outcome was clinically significant,
suggesting overall equivalency between the two procedures in short- and
midterm follow-up. A long-term randomized controlled trial with 7-year
follow-up further demonstrated equivalency between ACDF and TDA with
no significant differences in improvement of NDI, SF-36, and VAS scores for
both the arm and neck. However, there was a significant difference in the
need for secondary surgery; revision surgery rates were 18% in the ACDF
group and 7% in the TDA group.10 Ultimately, regarding single-level cervical
degenerative disease, both ACDF and TDA provide excellent clinical results
with good longevity. Although TDA may demonstrate some superior
outcomes, it is not suitable for all patients with degenerative cervical disk
disease. Some relative contraindications to TDA in this population include
degenerative instability, osteoporosis, loss of more than 50% of disk height,
and facet arthropathy.
For patients with multilevel cervical degenerative disease, a few
additional options exist for treatment. For two-level disease, surgeons have
suggested two-level ACDF, corpectomy and fusion, two-level TDA, and
hybrid constructs (ACDF at one level and TDA at another).
Regarding anterior fusion surgery, multilevel ACDF and corpectomy are
two effective treatment options (Figure 3), each with its own advantages.
Multilevel ACDF has potentially reduced blood loss, better ability to restore
sagittal alignment, and the opportunity for segmental fixation in the middle
vertebral body. Corpectomy allows decompression behind the vertebral body
and fewer graft-host interfaces at risk for pseudarthrosis. A systematic review
compiled the results of 10 studies that compared multilevel ACDF, multilevel
corpectomy, and ACDF-corpectomy hybrid procedures performed for CSM
and found that all procedures offered significant improvements in clinical
outcomes (VAS neck, VAS arm, NDI, and Japanese Orthopaedic Association
[JOA] scores).11 However, evidence supported superior improvements with
multilevel ACDF compared with both multilevel corpectomy and ACDFcorpectomy hybrid. Multilevel ACDF also allowed better restoration of
sagittal alignment. The results of this review suggest that when patient
pathology allows a choice in anterior fusion technique, multilevel ACDF is
likely the best option.
With respect to two-level fusion versus two-level TDA, 4-year follow-up
data from an FDA-approved prospective clinical trial was recently published
with results that favor TDA.12 Both cohorts demonstrated significant
improvements in symptoms postoperatively and had similar safety profiles.
However, the TDA group had significantly greater improvements in NDI,
SF-12 physical component summary scores, and patient satisfaction.
Revision surgery rates at the index levels were significantly lower in the TDA
group (4.0%) compared with the fusion group (15.2%); the most common
reason for reoperation in the fusion group was symptomatic pseudarthrosis.
The presence of radiographic adjacent-segment disease was significantly
higher in the fusion group, but the reoperation rates secondary to these
radiographic findings were not reported. Overall, these data suggest the
potential clinical superiority of two-level TDA compared with anterior fusion
at medium-term follow-up.
The final option for anterior surgery in multilevel CSM is a hybrid
procedure in which one level is treated with ACDF and the other with TDA.
This concept was examined from both biomechanical and clinical
perspectives in a systematic review.13 From a biomechanical aspect, hybrid
procedures had the capability to maintain the combined motion of the
surgical levels; therefore, it had no adverse effects on spinal kinematics,
intradiscal pressure of adjacent segments, or facet joint force. From a clinical
aspect, hybrid surgery demonstrated equivalent significantly improved
outcomes in NDI, VAS neck, and VAS arm scores, except for one study that
demonstrated better recovery in NDI and VAS neck scores for two-level
hybrid surgery compared with two-level ACDF. These results suggest a
potential role for hybrid surgery in the management of multilevel CSM;
however, no definitive conclusions can be made without further prospective
studies.
Figure 3
Images demonstrating anterior surgical options for
multilevel cervical spondylotic myelopathy. Preoperative
sagittal (A) and axial (B and C) magnetic resonance images show
compressive pathology at C5-6 and C6-7. The postoperative lateral
radiographs demonstrate two different treatment approaches: a twolevel diskectomy and fusion (D) or a C6 corpectomy and fusion (E).
Posterior Surgery: Decompression With Fusion and
Laminoplasty
Posterior approaches are typically chosen for multilevel CSM in patients with
neutral or maintained cervical lordosis. Specific indications for the use of
posteriorly based procedures can include the presence of posterior
compressive pathology or concern regarding the safety or feasibility of an
anterior approach. Posterior surgery allows for direct decompression through
the expansion or removal of the posterior elements, and an indirect
decompressive effect by allowing the spinal cord to float away from any
anterior pathology. Historically, multiple cervical laminectomies have a high
incidence of postoperative kyphosis, cervical instability, and subsequent
neurologic deterioration. As a result, cervical laminectomy has been replaced
by either motion-preserving laminoplasty or posterior cervical laminectomy
and fusion (Figure 4).
Decompressive laminoplasty relieves spinal cord compression by
elevating the posterior spinal elements en bloc while preserving the posterior
tension band and providing an anatomic restraint against postoperative
deformity. The results of laminoplasty for CSM have been good in the mid to
long term. A study with more than 20 years of patient follow-up indicated
that JOA and neurologic recovery scores were maintained at 10 years, but
demonstrated a decline in these measures at the most recent evaluation.
However, these declines often were a result of other unrelated spinal and
nonspinal pathology; therefore, laminoplasty is supported as a viable and
long-lasting treatment for CSM.
14
Compared with laminoplasty, posterior cervical decompression and
fusion performed for CSM removes the static components of compression by
means of a traditional laminectomy and eliminates the dynamic component of
the disease, lessening the risk of postoperative kyphosis, halting spondylotic
progression, and decreasing further neurologic insult secondary to pathologic
Figure 4
motion.
Skip laminectomy is another posteriorly based technique that is not
widely used.15 This procedure was initially developed as a less invasive
alternative to laminoplasty and is based on the premise of preserving the
posterior tension band through maintenance of the semispinalis and
multifidus attachments to each spinous process. In this technique, every other
lamina is removed after the associated spinous process is longitudinally
divided and removed from the lamina at the spinolaminar junction. After
decompression is complete, the split processes are then reapproximated,
restoring the posterior soft-tissue restraint. A literature review of alternative
treatment options for CSM compared skip laminectomy with traditional
laminoplasty and showed no difference in clinical outcomes of JOA, VAS
neck, or SF-12 scores. However, radiographic range of motion was better
preserved in the skip laminectomy group compared with traditional
laminoplasty, which suggests a possible benefit.16 Overall, definitive
evidence is lacking to recommend for or against skip laminectomy as a
laminoplasty alternative.
Images demonstrating posterior surgical options for
multilevel cervical spondylotic myelopathy. The
preoperative magnetic resonance image (A) shows compressive
cervical degenerative disease at multiple levels. Note the preservation
of cervical lordosis. The postoperative lateral radiographs demonstrate
two different treatment approaches: a posterior cervical
decompression and fusion (B) or cervical laminoplasty (C).
When comparing posterior surgical options, a systematic literature review
found that both laminoplasty and combined laminectomy and fusion are
equally efficacious in the treatment of CSM.17 The review involved four
retrospective cohort studies and demonstrated no definitive differences in
neurologic outcomes, neck pain scores, and postoperative kyphosis. Recent
data from the AOSpine North America and International study groups
corroborated these findings in a prospective multicenter study group and
demonstrated no difference between laminoplasty and combined
laminectomy and fusion in NDI scores, SF-36 scores, Nurick grades,
modified JOA scores, and complication rates.18 Given these data, no
recommendation can be made for either procedure over the other in the
treatment of CSM.
Anterior Versus Posterior Surgery
With multiple options available to surgically treat CSM and cervical
radiculopathy, choosing the appropriate procedure can be difficult. Most
discussion regarding surgical tactics has not centered on specific surgical
techniques, but rather the surgical approach. A systematic review of eight
level III retrospective cohort studies investigated anterior and posterior
approaches for the treatment of CSM.19 No difference in JOA and neck pain
scores was noted among cohorts and complication rates were not
significantly different. An individualized approach to treatment was
recommended based on patient pathoanatomy, preoperative deformity, and
focal or diffuse nature of the disease. Data from the AOSpine North America
CSM study group agreed with this recommendation after a retrospective
review of 264 surgically treated cases of CSM in which the surgeon selected
the approach based on patient pathology.20 The general guiding principles of
approach selection were to approach from the side of the pathology (anterior
for ventral compression and vice versa), to use anterior procedures only when
compression exists at three levels or fewer, and to use an anterior approach if
restoration of cervical lordosis is needed. Using these principles, no
difference in improvement was demonstrated in NDI, SF-36, and Nurick
scores. Notably, significantly more improvement was seen in modified JOA
scores in the posterior group, but after accounting for baseline disease
characteristics, this difference was no longer significant. Complication rates
were similar between patient cohorts.
Figure 5
Illustration depicting the common morphologic
presentations of ossification of the posterior longitudinal
ligament: localized (A), segmental (B), continuous (C), and mixed (D).
(Reproduced from An HS, Al-Shihabi L, Kurd M: Surgical treatment for
ossification of the posterior longitudinal ligament in the cervical spine.
J Am Acad Orthop Surg 2014;22[7]:420-429.)
Ossification of the Posterior Longitudinal Ligament
Ossification of the PLL is a specific pathologic entity in CSM that requires
special consideration when discussing surgical treatment options.
Ossification of the PLL is estimated to occur in up to 4.3% of patients with
cervical spine disorders in eastern Asian countries and up to 1.7% of patients
in North America.21 The disease process is characterized by degenerative
changes within the PLL that ultimately result in replacement of the normal
collagen structure with lamellar bone. The disease can be localized, involving
one level; segmental, involving several levels in a discontiguous manner; or
continuous (Figure 5). Most patients present with symptoms in the fifth or
sixth decade of life and up to 39% have myelopathy at the time of initial
presentation.
21
Decision making for surgical or nonsurgical treatment is the same as for
other patients with degenerative cervical spine disease; prophylactic surgery
plays no role in asymptomatic patients. A recent study compared outcomes of
surgical intervention for CSM caused by ossification of the PLL with other
causes and demonstrated equivalent clinical outcomes, although ossification
of the PLL was associated with a higher risk of perioperative complications,
specifically, superficial infection, new neck pain, and dural tears.22 No
changes were recommended to surgical decision making other than the
technical considerations necessitated by the pathoanatomy of the disease, and
decompression was advocated in the same manner as for other more common
forms of CSM.
When properly selected, both anterior and posterior approaches are
effective in the treatment of CSM secondary to ossification of the PLL.
Anterior surgery is most commonly performed for localized disease (fewer
than three levels), for patients with symptoms of radiculopathy that
predominate over symptoms of myelopathy, and in instances of cervical
kyphosis. In addition to restoring lordosis, another advantage to anterior
surgical intervention is the ability to directly treat the compressive pathology.
The primary disadvantage of anterior surgical intervention in ossification of
the PLL is a high rate of dural tears, which can range from 6.7% to 31.8%
22
secondary to adhesions and/or ossification of the dura, which can occur in up
to 15% of cases.
21
Posterior surgical intervention consists of indirect decompression by
means of either laminoplasty or combined laminectomy and fusion and
typically is recommended for patients with more extensive disease (greater
than three levels), for patients with a congenitally stenotic canal, and for
patients with preserved cervical lordosis. To determine if an acceptable
amount of cervical lordosis exists for posterior intervention, a kyphosis line
(K-line) should be drawn from the center of the C2 canal to the center of the
C7 canal. If the K-line passes through the PLL ossification mass, posterior
surgical intervention should be avoided because outcomes were significantly
inferior to outcomes in patients in whom the K-line passed posterior to the
compressive pathology23 (Figure 6).
Combined anterior-posterior approaches are another option for the
treatment of ossification of the PLL, specifically in instances of multilevel
disease in the setting of cervical kyphosis. A limited anterior procedure can
help restore cervical lordosis, which allows the multilevel posterior procedure
to indirectly decompress the neural elements (Figure 7). This approach
avoids the problems associated with extensive anterior dissection and
maximizes the efficacy of the posterior decompression by correcting the
sagittal deformity. Posterior fixation also can be useful as a salvage surgery
in cases of pseudarthrosis resultant from a prior anterior procedure.
Figure 6
Illustrations demonstrate how the kyphosis line (K-line; blue
line) can help predict the effectiveness of posterior surgical
decompression in patients with cervical spondylotic myelopathy
secondary to ossification of the posterior longitudinal ligament by
determining if enough lordosis exists to allow the spinal cord to float
away from the posterior longitudinal ligament mass. A, If the K-line
passes posterior to the ossification mass, the patient is a good
candidate for posterior surgical intervention. B, If the K-line passes
through the posterior longitudinal ligament ossification mass, surgical
intervention should be avoided.
Outcome differences in approach have been highlighted in several clinical
studies. One study evaluated 5-year outcomes of patients with CSM
secondary to ossification of the PLL treated with either ACDF or
laminoplasty.24 The preoperative cervical alignment and the degree of canal
compromise were important considerations. In patients with more than 50%
canal compromise from ossification of the PLL, ACDF resulted in
significantly superior neurologic outcomes compared with laminoplasty.
Regarding alignment, patients with preoperative kyphosis demonstrated a
significantly higher neurologic recovery rate in the ACDF group than did
those in the laminoplasty group. A retrospective study of patients with
ossification of the PLL occupying greater than 60% of the canal had
significantly better outcomes when treated with ACDF. In addition, in
patients treated with laminoplasty, good or excellent outcomes were more
common in patients with a greater degree of cervical lordosis.
25
Complications of Surgical Intervention
The literature on surgical decompression for CSM has repeatedly shown
significantly more favorable patient functional outcomes in surgical cohorts
compared with their nonsurgical counterparts. Given the high incidence of
disease progression and neurologic decline, the consensus for surgical
treatment is almost universal. However, some risks need to be considered,
especially in the patient with myelopathy. A recent retrospective review of
the American College of Surgeons National Surgical Quality Improvement
Program database showed that patients with myelopathy undergoing ACDF
had a ninefold greater likelihood of mortality, were 1.8 times more likely to
experience a severe adverse event, and were 1.5 times more likely to
experience any adverse event than patients without myelopathy.26 A recent
multicenter prospective study by the AOSpine North America group reported
an overall rate of 18.7% for postoperative adverse events; the three most
commonly reported were dysphagia (3.6%), superficial infection (2.9%), and
cardiopulmonary events (2.5%).
27
Intraoperative Complications
Several complications are associated with surgical decompression for CSM,
ranging from dental injury during intubation to intraoperative spinal cord
injury. The exact rates of these complications are difficult to determine, given
the differences in reporting practices, although a 2015 study meticulously
collected adverse event data for a cohort of 104 patients with CSM who
underwent decompression using various surgical approaches.28 An
intraoperative adverse event rate of 13.5% was reported, the most common of
which was intraoperative hardware-related issues: 4.9% of patients required
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