This A/B MAC considers United States Food and Drug Administration
(FDA)-approved prosthetic cervical discs reasonable and necessary for the
treatment of Medicare Beneficiaries with symptomatic cervical degenerative
disease or herniated disc at a single level when _all_ of the following
criteria are met:

  1. The device is approved by the FDA AND
  2. The Beneficiary is skeletally mature AND
  3. The Beneficiary has EITHER: 
    1. Intractable cervical radicular pain or myelopathy which has failed at least 6 weeks of conservative  
non-operative treatment, including physician-directed pain management (e.g.,
pharmacotherapy  
addressing neuropathic pain and physical therapy) OR

    2. Beneficiary has severe or rapidly progressive symptoms of nerve root or spinal cord compression  
requiring hospitalization or immediate surgical intervention, AND

  4. The Beneficiary must have clinical evidence of corresponding nerve root or spinal cord compression  
documented by computed tomography (CT), myelography, or magnetic resonance
imaging (MRI), AND

  5. Cervical degenerative disc disease (CDDD) is from C3 to C7, AND
  6. The Beneficiary is free from absolute contraindications to cervical disc replacement (CDR) which include: 
    1. Extreme obesity (BMI > 40 kg/m2)
    2. Significant cervical anatomical deformity
    3. Allergy or sensitivity to implant materials (cobalt, chromium, molybdenum, polyethylene, titanium)
    4. Active systemic infection or infection at the operating site
    5. Osteoporosis or osteopenia
    6. Marked cervical instability on resting lateral or flexion/extension radiographs demonstrated by  
translation greater than 3.5 mm, and/or greater than 11 angular difference to
that of either level  
adjacent the treated level

    7. Severe spondylosis
    8. Clinically compromised vertebral bodies at affected level
  7. Two-level procedures performed simultaneously may be considered reasonable and necessary if there is  
objective clinical evidence of radiculopathy, myelopathy or spinal cord
compression at 2 corresponding  
contiguous levels. A CDR device FDA-approved for 2 levels is required.

CDR is considered investigational for all other indications and conditions
including:

  * Disc replacement at 2 non-contiguous levels or 3 or more levels
  * Combined use of an artificial cervical disc and fusion
  * Prior surgery at the treated level
  * Previous fusion at another level
  * Any anatomical deformity (e.g., ankylosing spondylitis, trauma)
  * Any autoimmune disease or rheumatoid arthritis
  * Moderate to severe facet joint arthropathy at the involved level
  * Metabolic bone disease (e.g., osteoporosis, Paget's disease, osteomalacia, osteogenesis imperfecta) or taking medications known to potentially interfere with bone/soft tissue healing (e.g., steroids)
  * Malignancy
  * Chronic renal failure

Optimal outcomes of CDR procedures depend on the knowledge, skill and
experience of the provider. Consequently, the provider performing the
procedure must be capable of demonstrating documented training and experience
relevant to cervical spine surgery.

Services will be considered medically reasonable and necessary only if
performed by appropriately trained providers.

  * All CDR procedures must be performed by a licensed qualified physician
  * A licensed qualified physician for these services is defined as:
    * Having trained and acquired expertise within the framework of an accredited residency **or** fellowship program in the applicable specialty/subspecialty (e.g., neurosurgery, orthopedic spine) **or** must reflect equivalent education, training and expertise endorsed by an academic institution in spine surgery **or** by applicable specialty/subspecialty society, **and**
    * Is able to provide evidence of proficiency in the performance and management of CDR and CDDD.

Neck pain is highly prevalent with approximately 15-20% of adults reporting at
least 1 episode during any given year with degenerative disc disease (DDD) as
a frequent cause.1 Aging is the primary risk in developing DDD. As the United
States (U.S.) population ages, the incidence of CDDD has increased in kind.
Though the initial treatment is typically conservative, the frequency of
cervical spine surgeries in the U.S. has increased substantially, with a
retrospective study finding the annual number of fusions for cervical
spondylotic myelopathy increasing from 3,879 in 2003 to 8,181 in 2013.2 The
study also found that the average age of all fusion patients increased from
58.2 to 60.6 years (p<0.01).2 Disc herniation, osteophytes, or an instability
that compresses the cervical spinal cord can result in myelopathy, manifested
by paresthesia, pain, or weakness of the arms or hands.

Anterior cervical discectomy and fusion (ACDF) has historically been
considered the definitive surgical treatment for symptomatic DDD of the
cervical spine. The goals of ACDF are to relieve pressure on the spinal nerves
(decompression) and to restore spinal column alignment and stability. CDR is a
new surgical strategy that has recently emerged as a possible alternative to
ACDF, the more commonly used decompressive procedure in the cervical spine. In
CDR, an artificial disc is secured in the prepared intervertebral space rather
than an interbody cage and/or bone. Since an anterior plate is not required to
stabilize the adjacent vertebrae and postsurgical orthosis is not usually
required, it is hypothesized that CDR's advantage is its ability to maintain
anatomical disc space height, normal segmental lordosis, and physiological
motion patterns at the index and adjacent cervical level with reduced risk of
adjacent-level DDD, commonly seen above or below a fusion site.3

CDR is equivalent to ACDF for surgical treatment of CDDD in select patient
groups with the advantage of preserving motion.

Mummaneni, et al. (2007) reported the results of a prospective, randomized,
multi-center study in which the results of CDR with the Prestige ST Cervical
Disc System (Medtronic Sofamor Danek) were compared with ACDF.4 Patients with
symptomatic single-level CDDD who failed at least 6 weeks of conservative
treatment, or had signs of progression or spinal cord/nerve root compression
with continued non-operative care, were included in the study. DDD was
determined to be present if a herniated disc and/or osteophyte formation were
confirmed by history and radiographic studies (e.g., CT, MRI, x-rays). A total
of 541 patients were enrolled at 32 sites and randomly assigned to 1 of 2
treatment groups: (i) 276 patients in the investigational group underwent
anterior cervical discectomy and decompression and replacement with the
Prestige ST Cervical Disc System; and (ii) 265 patients in the control group
underwent decompressive ACDF. A total of 80% of the arthroplasty-treated
patients (223 of 276) and 75% of the control patients (198 of 265) completed
clinical and radiographic follow-up (FU) examinations at routine intervals for
2 years after surgery.4 Analysis of available post-operative 12- and 24-month
data indicated a 2-point greater improvement in the neck disability index
(NDI) score in the investigational group than the control group.4 The
arthroplasty group also had a statistically significant higher rate of
neurological success (p=0.005), as well as a lower rate of secondary revision
surgeries (p=0.0277) and supplemental fixation (p=0.0031).4 The mean
improvement in the 36-Item Short Form Health Survey (SF-36) Physical Component
Summary scores was greater in the investigational group at 12 and 24 months,
as was relief of neck pain. The patients in the investigational group returned
to work 16 days sooner than those in the control group, and the rate of
adjacent-segment re-operation was significantly lower in the investigational
group as well (p=0.0492, log-rank test).4 The cervical disc implant maintained
segmental sagittal angular motion averaging more than 7 degrees. In the
investigational group, there were no cases of implant failure or migration.
The authors concluded that the Prestige Cervical Disc maintained
physiological segmental motion at 24 months after implantation and was
associated with improved neurological success, improved clinical outcomes, and
a reduced rate of secondary surgeries compared with ACDF.4 The FDA approved
the Prestige Cervical Disc (Medtronic Sofamor Danek, Memphis, TN) for the
treatment of single-level CDDD (C3 to C7) in 2007.

Sasso, et al. (2007) evaluated the functional outcome and radiographic results
of the BRYAN artificial CDR for patients with 1-level cervical disc disease.5
Twelve-month FU was available for 110 patients and 24-month FU was completed
for 99 patients. There were 30 males and 26 females in the investigational
group, and 32 males and 27 females in the fusion group. The average age was 43
years (investigational) and 46 years (fusion). Disability and pain were
assessed using the NDI and the VAS (Visual Analog Scale) of the neck and of
the arm pain. SF-36 outcome measures were obtained, including the physical
component as well as the mental component scores. Range of motion (ROM) was
determined by independent radiologic assessment of flexion-extension
radiographs. The average operative time for the control group was 1.1 hours
and the investigational group 1.7 hours. Average blood loss was 49 ml
(control) and 64 ml (investigational). Average hospital stay was 0.6 days
(control) and 0.9 days (investigational). The mean NDI before surgery was not
statistically different between groups: 47 (investigational) and 49 (control).
Twelve-month FU NDI was 10 (investigational) and 18 (control) (p=0.013).5 At
2-year FU, NDI for the investigational group was 11 and the control group was
20 (p=0.005).5 The mean arm pain VAS before surgery was 70 (investigational)
and 71 (control). At 1-year FU, investigational arm pain VAS was 12 and
control 23 (p = 0.031). At 2-year FU, the average arm pain VAS for the
investigational group was 14 and control 28 (p = 0.014). The mean neck pain
VAS before surgery was 72 (investigational) and 73 (control); 1-year FU scores
were 17 (investigational) and 28 (control) (p = 0.05); 2-year FU: 16
(investigational) and 32 (control) (p=0.005). SF-36 scores: Physical component
before surgery investigational 34 and control 32; at 24 months:
investigational 51 and control 46 (p=0.009). More motion was retained after
surgery in the disc replacement group than the plated group at the index level
(p<0.006 at 3, 6, 12, and 24 months).5 The disc replacement group retained an
average of 7.9 degrees of flexion-extension at 24 months. In contrast, the
average ROM in the fusion group was 0.6 degrees at 24 months. There were 6
additional operations in this series: 4 in the control group and 2 in the
investigational group. There were no intra-operative complications, no
vascular or neurological complications, no spontaneous fusions, and no device
failures or explanations in the investigational cohort. The authors concluded
that the BRYAN artificial disc replacement compared favorably to ACDF for the
treatment of patients with 1-level cervical disc disease. At the 2-year FU,
there are statistically significant differences between the groups with
improvements in the NDI, the neck pain and arm pain VAS scores, and the SF-36
physical component score in the investigational disc population.5

In 2007, the FDA approved the ProDiscTM-C Total Disc Replacement (Synthes
Spine, Inc.) for use in skeletally mature patients for reconstruction of the
disc from C3-C7 following removal of the disc at 1 level for intractable
symptomatic cervical disc disease (SCDD). The FDA's approval was based upon
the results of a clinical trial (non-inferiority) involving 209 patients at 13
clinical sites comparing ProDiscTM-C to ACDF.6 Patients with SCDD who failed at
least 6 weeks of non-operative treatment or had progressive symptoms or signs
of nerve root/spinal cord compression in the face of conservative treatment,
qualified for the trial. Intractable SCDD was defined as neck or arm
(radicular) pain, and/or a functional/neurological deficit with at least 1 of
the following conditions confirmed by imaging (CT, MRI, or x-rays): (i)
herniated nucleus pulposus, (ii) spondylosis (defined by the presence of
osteophytes), or (iii) loss of disc height. Patients were evaluated for pain
and disability, neurological status and ROM at the index level. Patients were
followed for 2 years post-surgery. The study data indicated that the
ProDiscTM-C is non-inferior to ACDF. According to the FDA-approved labeling,
the ProDiscTM-C should not be implanted in patients with an active infection,
allergy to any of the device materials, osteoporosis, marked cervical
instability, severe spondylosis, clinically compromised vertebral bodies at
the level to be treated, and SCDD at more than 1 level.6

In 2009, the FDA-approved the BRYAN Cervical Disc (Medtronic Sofamor Danek)
for use in skeletally mature patients for reconstruction of the disc from
C3-C7 following single-level discectomy for intractable radiculopathy and/or
myelopathy. The FDA's approval of the BRYAN Cervical Disc was based upon the
results of a clinical trial (non-inferiority) involving 463 patients at 30
clinical sites comparing the BRYAN device to ACDF.7 Patients with intractable
radiculopathy and/or myelopathy resulting in impaired function with at least 1
clinical neurological sign associated with the cervical level to be treated,
and who failed at least 6-weeks of conservative treatment, qualified for the
trial. Intractable radiculopathy and/or myelopathy were defined as any
combination of the following conditions confirmed by imaging (CT, myelography
and CT, and/or MRI): (i) disc herniation with radiculopathy, (ii) spondylotic
radiculopathy, (iii) disc herniation with myelopathy, or (iv) spondylotic
myelopathy. Patients were evaluated for pain and disability, and neurological
status. Patients were followed for 2 years post-surgery. The study data
indicated that the investigational CDR is non-inferior to ACDF.7 According to
the FDA-approved labeling, the BRYAN Cervical Disc should not be implanted in
patients with an active infection, allergy to any of the device materials,
osteoporosis, moderate to advanced spondylosis, marked cervical instability,
significant cervical anatomical deformity or compromised vertebral bodies at
the index level, significant kyphotic deformity or significant reversal of
lordosis, or symptoms necessitating surgical treatment at more than 1 cervical
level. Because the specific polyurethanes used in the device have not been
exhaustively studied for use as sheaths or nuclei in a cervical disc
prosthesis, the FDA recommended that the sponsor continue to evaluate
explanted devices in a 10 year post-approval study.

The FDA approved the SECURE-C Artificial Cervical Disc in 2012 based on the
results of a non-inferiority study, which is intended to be used in skeletally
mature patients to replace a cervical disc (from C3 to C7) following removal
of the disc for conditions that result from a diseased or bulging disc
(intractable radiculopathy or myelopathy) at only 1 level.8 The Investigation
Device Exemption (IDE) trial compared the clinical safety and effectiveness of
the selectively constrained SECURE-C (Globus Medical) Cervical Artificial
Disc to ACDF. The study results demonstrated statistical superiority of the
randomized investigational CDR group compared with the randomized ACDF group
at 24 months, with a posterior probability of 100% using the protocol-
specified criteria and 98.1% using FDA-defined criteria. At 24 months
postoperatively, the investigational CDR group demonstrated clinically
significant improvement in pain and function in terms of NDI, VAS, and SF-36.
At 24 months, the percentage of patients experiencing secondary surgical
interventions at the index level was statistically lower for the
investigational CDR group (2.5%) than the ACDF group (9.7%).8

Contraindications of the Secure-C Artificial Cervical Disc:

  * Active systemic infection or an infection at the operating site
  * Allergy to the metals in the device (cobalt, chromium, molybdenum, or titanium), or to the type of plastic used in the device (polyethylene)
  * Facet joint arthropathy
  * More than 1 cervical disc requiring treatment (since device has only been evaluated in patients with 1 cervical disc requiring treatment)
  * Osteoporosis or osteopenia
  * Severe spondylosis
  * Unstable cervical spine
  * Weakened bones at the affected level due to current or past trauma

**Safety and efficacy of 2-level CDR**

On August 23, 2013, the FDA approved the Mobi-C Cervical Disc Prosthesis for
2-level cervical disease. However, pivotal clinical studies excluded patients
with degenerative joint disease (DJD) at more than 1-level. Beaurain, et al.
reported the intermediate results of an undergoing multi-center prospective
study of total disc replacement (TDR) with Mobi-C prosthesis.9 These
researchers evaluated (i) the safety and effectiveness of the device in the
treatment of DDD and (ii) the radiological status of adjacent levels and the
occurrence of ossifications, at 2-year FU. A total of 76 patients had
performed their 2-year FU visit and had been analyzed clinically and
radiologically. Clinical outcomes (NDI, VAS, SF-36) and ROM measurements were
analyzed pre-operatively and at the different post-operative time-points.
Complications and re-operations were also assessed. Occurrences of heterotopic
ossifications (HOs) and of adjacent disc degeneration radiographic changes
have been analyzed from 2-year FU X-rays. The mean NDI and VAS scores for arm
and neck were reduced significantly at each post-operative time-point compared
to pre-operative condition. Motion was preserved over the time at index levels
(mean ROM = 9 degrees at 2 years) and 85.5% of the segments were mobile at 2
years. HOs were responsible for the fusion of 6/76 levels at 2 years. However,
presence of HO did not alter the clinical outcomes.9 The occurrence rate of
radiological signs of adjacent-level degeneration (ALD) was very low at 2
years (9.1%). There had been no subsidence, no expulsion and no sub-luxation
of the implant. The authors concluded that these intermediate results of TDR
appeared to confirm the safety and effectiveness of the device.9

Huppert, et al. (2011) compared the safety and effectiveness of disc
replacement with an unconstrained prosthesis in multi- versus single-level
patients.10 A total of 231 patients with CDDD who were treated with CDR and
completed their 24 months FU were analyzed prospectively: 175 were treated at
1-level, and 56 at 2-level or more.10 Comparison between both groups was based
on usual clinical and radiological outcomes (NDI, VAS, ROM, satisfaction).
Safety assessments, including complication and subsequent surgeries, were also
documented and compared. Mean NDI and VAS scores for neck and arm pain were
improved in both groups similarly. Improvement of mobility at treated segments
was also similar. Nevertheless, in the multi-level group, analgesic use was
significantly higher; and occurrence of HOs was significantly lower than in
the single-level group. Subject satisfaction was nearly equal, as 94.2% of
single-level group patients would undergo the surgery again versus 94.5% in
the multi-level group.10 The overall success rate did not differ
significantly. Multi-level DDD is a challenging indication in the cervical
spine. This study showed no major significant clinical difference between the
2 groups.10 The major drawbacks of this exploratory study were small sample
size, lack of randomization, and the p values suggested a trend towards
similar results in the outcomes of single-level versus multi-level
populations.

Davis, et al. (2013) compared the Mobi-C cervical artificial disc to ACDF for
treatment of CDDD at 2 contiguous levels of the cervical spine.11 The primary
clinical outcome was a composite measure of study success at 24 months. The
comparative control treatment was ACDF using allograft bone and an anterior
plate. A total of 330 patients were enrolled, randomized, and received study
surgery. All patients were diagnosed with intractable SCDD at 2 contiguous
levels of the cervical spine between C3 and C7. Patients were randomized in a
2:1 ratio (TDR patients to ACDF patients). A total of 225 patients received
the investigational CDR device and 105 patients received ACDF. At 24 months,
only 3.0% of patients were lost to FU.11 On average, patients in both groups
showed significant improvements in NDI score, VAS neck pain score, and VAS arm
pain score from pre-operative baseline to each time-point. However, the CDR
patients experienced significantly greater improvement than ACDF patients in
NDI score at all time-points, and significantly greater improvement in VAS
neck pain score at 6 weeks, and at 3, 6, and 12 months post-operatively. On
average, patients in the CDR group also maintained pre-operative segmental ROM
at both treated segments immediately postoperatively and throughout the study
period of 24 months. The re-operation rate was significantly higher in the
ACDF group at 11.4% compared with 3.1% for the CDR group.11 Furthermore, at 24
months, CDR demonstrated statistical superiority over ACDF based on overall
study success rates.11 The authors concluded that the results of this study
represented the first available Level I clinical evidence in support of
cervical arthroplasty at 2 contiguous levels of the cervical spine using the
Mobi-C cervical artificial disc. Moreover, they stated that additional
rigorous research will further the understanding of the safety and
effectiveness of multi-level cervical arthroplasty and arthrodesis
procedures.11

Alvin and Mroz (2014) evaluated the available literature on CDR with the
Mobi-C prosthesis, with a focus on 2-level CDR.12 All clinical articles
involving the investigational disc prosthesis for CDR through September 1,
2014 were identified on Medline. Any paper that presented Mobi-C CDR clinical
results was included. Study design, sample size, length of FU, use of
statistical analysis, quality of life outcome scores, conflict of interest,
and complications were recorded. A total of 15 studies were included but only
1 of which was a level Ib randomized controlled trial (RCT). All studies
included showed non-inferiority of 1-level CDR to 1-level ACDF. Only 1 study
analyzed outcomes of 1-level versus 2-level CDR, and only 1 study analyzed
2-level CDR versus 2-level ACDF. In comparison with other cervical disc
prostheses, the Mobi-C prosthesis is associated with higher rates of HO.
Studies with conflicts of interest reported lower rates of HO. Adjacent
segment disease or degeneration along with other complications was not
assessed in most studies. The authors concluded that 1-level Mobi-C CDR is
non-inferior, but not superior, to 1-level ACDF for patients with CDDD.12 They
stated that Mobi-C CDR procedure is associated with high rates of HO.
However, they noted that insufficient evidence exists, thereby mandating a
need for unbiased, well-designed prospective studies with well-defined
outcomes in the future.12

In a meta-analysis, Zhao, et al. (2015) estimated the effectiveness of multi-
level CDR over single-level CDR for the treatment of cervical spondylosis and
disc diseases.13 To compare the studies of multi-level CDR versus single-level
CDR in patients with cervical spondylosis that reported at least 1 of the
following outcomes: functionality, neck pain, arm pain, quality of life, re-
operation and incidence of HO, electronic databases (Medline, Embase, PubMed,
Cochrane library, and Cochrane Central Register of Controlled Trials) were
searched. No language restrictions were used; 2 authors independently assessed
the methodological quality of included studies and extracted the relevant
data. Out of 8 cohorts that were included in the study, 4 were prospective
cohorts and the other 4 were retrospective. The results of the meta-analysis
indicated that there was no significant difference in NDI, neck VAS, arm VAS,
morbidity of re-operation, HO, and parameters of living quality when comparing
multi-level CDR with single-level CDR at 1 and 2 years FU post-operatively
(p>0.05).13 The authors concluded that the findings of this meta-analysis
revealed that the outcomes and functional recovery of patients performed with
multi-level CDR were equivalent to those with single-level cervical disc
arthroplasty (CDA), which suggested the multi-level CDR was as safe and
effective as single-level invention for the treatment of cervical
spondylosis.13

A prospective randomized, FDA investigational device exemption pivotal trial
of the Mobi-C cervical artificial disc was conducted at 24 centers in the
U.S.14 A total of 330 patients with DDD were randomized and treated with
cervical TDR (225 patients) or the control treatment, ACDF (105 patients).
Patients were followed-up at regular intervals for 4 years after surgery. At
48 months, both groups demonstrated improvement in clinical outcome measures
and a comparable safety profile. Data were available for 202 CDR patients and
89 ACDF patients in calculation of the primary end-point. CDR patients had
statistically significantly greater improvement than ACDF patients for the
following outcome measures compared with baseline: NDI scores, 12-Item Short
Form Health Survey (SF-12) Physical Component Summary scores, patient
satisfaction, and overall success. ACDF patients experienced higher subsequent
surgery rates and displayed a higher rate of ALD as seen on radiographs.
Overall, CDR patients maintained segmental ROM through 48 months with no
device failure. The authors concluded that 4-year results from this study
continue to support CDR as a safe, effective, and statistically superior
alternative to ACDF for the treatment of DDD at 2 contiguous cervical
levels.14

In a prospective, randomized, multi-center FDA-IDE study using CDR as surgical
treatment of DDD at 1 or 2 contiguous levels of the cervical spine, Bae, et
al. (2015) evaluated the safety and effectiveness of CDR at single or 2
contiguous levels through 48 months of FU.15 Patients were randomized in a 2:1
ratio (CDR: ACDF) at 24 sites. Ultimately, 164 patients received TDR at 1
level and 225 patients received CDR at 2 contiguous levels. An additional 24
patients (15 1-level, 9 2-level) were treated with CDR as training cases.
Outcome measures included NDI, VAS neck and arm pain, SF-12 Mental Composite
Score (MCS) and Physical Composite Score (PCS), ROM, major complication rates,
and secondary surgery rates. Patients received FU examinations at regular
intervals through 4 years after surgery. Pre-operative characteristics were
statistically similar for the 1- and 2-level patient groups. Four-year FU
rates were 83.1% (1-level) and 89.0% (2-level). There was no statistically
significant difference between 1- and 2-level CDR groups for all clinical
outcome measures. Both CDR groups experienced significant improvement at each
FU when compared with pre-operative scores. One case of migration was reported
in the 2-level CDR group. The authors concluded that a 4-year post hoc
comparison of 1- and 2-level CDR patients concurrently enrolled in a
24-center, FDA-IDE clinical trial indicated no statistical differences between
groups in clinical outcomes, overall complication rates, and subsequent
surgery rates.15

In a prospective, multi-center, randomized, un-blinded clinical trial,
Jackson, et al. (2016) evaluated subsequent surgery rates up to 5 years in
patients treated with CDR or ACDF at 1 or 2 contiguous levels between C3 and
C7.16 Patients with symptomatic DDD were enrolled to receive 1- or 2-level
treatment with either CDR as the investigational device or ACDF as the control
treatment. There were 260 patients in the 1-level study (179 CDR and 81 ACDF
patients) and 339 patients in the 2-level study (234 CDR and 105 ACDF
patients). At 5 years, the occurrence of subsequent surgical intervention was
significantly higher among ACDF patients for 1-level (CDR, 4.5% [8/179]; ACDF,
17.3% [14/81]; p=0.0012) and 2-level (CDR, 7.3% [17/234]; ACDF, 21.0%
[22/105], p=0.0007) treatment. The CDR group demonstrated significantly fewer
index- and adjacent-level subsequent surgeries in both the 1- and 2-level
cohorts. The authors concluded that 5-year results showed treatment with CDR
results in a significantly lower rate of subsequent surgical intervention than
treatment with ACDF for both 1 and 2 levels of treatment. The main drawbacks
of this study included: (i) the inability to blind surgeons and patients to
treatment, which opened the results to the potential of confirmation bias.
Although the control group in this study was limited to anterior plating with
allograft, other fusion procedures and devices (e.g., standalone devices and
the use of autograft) were viable treatment options, (ii) the comparative
results between the control and investigational groups were limited to
anterior plate and allograft and may not be consistent with those of other
surgical alternatives for cervical fusion, and (iii) the control group
consisted of patients receiving 3 different cervical plate systems, based on
surgeon preference. This heterogeneity represented a study limitation because
ACDF failures may not have been equally distributed across the 3 fusion
systems implanted.16

**Long-term safety and efficacy outcomes of CDR**

Quan, et al. (2011) evaluated the long-term outcome of CDR.17 A total of 21
patients underwent 27 total disc arthroplasties using the BRYAN cervical disc
after anterior cervical discectomy. Clinical and radiological data were
obtained from the 8-year post-operative review. Nineteen of 21 patients were
able to perform daily activities without limitation; 20 of 21 patients
reported fair to excellent outcome according to Odom criteria and 21 of 27
(78%) operated segments were mobile. Functional prostheses moved an average of
10.6, which was similar to the range of movement of the adjacent non-operated
segments of the cervical spine. HO was evident in 13 of the 27 (48%) operated
segments and restricted movement of the prosthesis in 9 cases. Five of the 6
patients who received bi-level disc replacements developed HO. There was 1
case of posterior migration of the prosthesis, which did not have any clinical
repercussion. No other case showed evidence of migration, subsidence,
loosening, or wear. Radiological evidence of ALD was observed in 4 patients
(19%); however, each of these patients had pre-existing DDD at these levels on
pre-operative imaging. The authors concluded that at 8-year FU, the BRYAN CDA
maintains favorable clinical and radiological results, with preservation of
movement and satisfactory clinical outcome in the majority of cases.17
However, the incidence of HO causing restricted range of movement of the
prosthesis appears to increase with time, especially in bi-level procedures.17

Coric, et al. (2013) evaluated the long-term results of CDR and ACDF in the
treatment of single-level cervical radiculopathy.18 The results of 2 separate
prospective, randomized, FDA-IDE pivotal trials (BRYAN Disc and KineFLEX|C)
from a single investigational site were combined to evaluate outcomes at long-
term FU. The primary clinical outcome measures included the NDI, VAS, and
neurological examination. Patients were randomized to receive CDR in 2
separate prospective, randomized studies using the BRYAN Disc or KineFLEX|C
cervical artificial disc compared with ACDF using structural allograft and an
anterior plate. Patients were evaluated pre-operatively; at 6 weeks; at 3, 6,
and 12 months; and then yearly for a minimum of 48 months. Plain radiographs
were obtained at each study visit. A total of 74 patients were enrolled and
randomly assigned to either the CDR (n=41) or ACDF (n=33) group. A total of 63
patients (86%) completed a minimum of 4 years FU. Average FU was 6 years (72
months) with a range from 48 to 108 months. In both the CDR and ACDF groups,
mean NDI scores improved significantly by 6 weeks after surgery and remained
significantly improved throughout the minimum 48-month FU (p<0.001).18
Similarly, the median VAS pain scores improved significantly by 6 weeks and
remained significantly improved throughout the minimum 48-month FU
(p<0.001).18 There were no significant differences between groups in mean NDI
or median VAS scores. The ROM in the CDR group remained significantly greater
than the pre-operative mean, whereas the ROM in the ACDF group was
significantly reduced from the pre-operative mean. There was significantly
greater ROM in the CDR group compared with the ACDF group. There were 3
reoperations (7.3%) at index or adjacent levels in the CDR group; all were
cervical lamino-foraminotomies. There were 2 adjacent level reoperations in
the CDR group (4.9%). There was 1 reoperation (3.0%) in the ACDF group at an
index or adjacent level (a second ACDF at the adjacent level). There was no
statistically significant difference in overall reoperation rate or adjacent
level reoperation rate between groups. The authors concluded that both CDR and
ACDF groups showed excellent clinical outcomes that were maintained over long-
term FU. Both groups showed low index-level and adjacent level reoperation
rates. Both CDR and ACDF appeared to be viable options for the treatment of
single-level cervical radiculopathy.18

Ren, et al. (2014) evaluated the mid- to long-term clinical outcomes after CDR
as compared with ACDF for the treatment of SCDD.19 A systematic review and a
meta-analysis were performed for articles published up to March 2013. RCTs
that reported mid- to long-term outcomes (greater than or equal to 48 months)
after CDR as compared with ACDF were included. Two authors independently
extracted the articles and the predefined data. A total of 5 RCTs that
reported 4 to 6 years of FU data were retrieved. Patients who underwent CDR
had a lower mid- to long-term rate of reoperation and had greater mid- to
long-term improvements in the NDI, neck and arm pain scores, and SF-36
physical component score than did those who underwent ACDF. Segmental motion
was maintained in patients who underwent CDR. The mid- to long-term rates of
adjacent segment disease and neurological success were not significantly
different between the 2 groups. The authors concluded that CDR may result in
better mid- to long-term functional recovery and a lower rate of subsequent
surgical procedures than ACDF would. Moreover, they stated that a review of
the literature showed that only an insufficient number of studies had
investigated adjacent segment disease; therefore, it is mandatory that
adequate future research should focus in this direction.19

In a 10-year FU prospective, randomized-controlled clinical trial published in
2018 by Lavelle, et al., 128 (CDR) and 104 (ACDF) patients were available for
evaluation. Overall success rate was significantly higher for CDR group (81.3%
vs. 66.3%; p=0.005). Mean angular motions at index level for BRYAN disc and
ACDF were 8.69 and 0.60 respectively. These results confirm long-term
preservation of motion in CDR compared to ACDF.20

Moreover, artificial disc replacement was assessed by the Washington State
Health Technology Clinical Committee March 17, 2017, who concluded that CDRs
were at least equivalent for safety and effectiveness compared to alternatives
for some conditions.

Level of evidence - Moderate (I-IIb, with risks of bias)

Strength of recommendation - Moderate

CMS published a national non-coverage decision for lumbar artificial disc
replacement in Medicare Beneficiaries older than 60 years of age; however,
there is no national coverage determination (NCD) for CDR leaving it to be
made on a local basis.

Based on the best available evidence, patients who have symptoms and signs of
cervical radiculopathy, cervical root compression by advanced imaging at the
corresponding side or level, and progressive motor weakness are appropriate
candidates for surgery rather than nonsurgical therapy.21 A critical mass of
level 1-2b evidence, including data with multiple FDA-approved devices at
multiple sites with short-, mid-, and long-term FU is compelling enough to
consider CDR as a reasonable option for surgical treatment of CDDD in select
patients.