REVIEW

Past, Present, and Future of Cervical Arthroplasty
Chang Hyun Oh1 and Seung Hwan Yoon2
1 Department of Neurosurgery, Guro Teun Teun Hospital, Seoul, Korea

2 Department of Neurosurgery, Inha University Hospital, Incheon, Korea(Received for publication on September 5, 2012)(Accepted for publication on January 18, 2013)

Cervical arthroplasty was developed in an attempt to maintain cervical motion and potentially to avoid
or minimize adjacent-segment degeneration. If cervical arthroplasty is successful, the long-term resultsof surgery for cervical disc disease should improve. However, problems associated with cervical arthroplasty have been reported: these include kyphosis, heterotopic ossification-induced motion limitation,
no motion preservation even at the index level, and a higher revision rate in a limited number of cases
compared with anterior cervical discectomy and fusion (ACDF). In addition, for degenerative cervicaldisc disorders, the risk of developing adjacent segment degeneration more than 2 years after surgery
is reportedly similar for ACDF and cervical arthroplasty. Cervical disc arthroplasty is an emerging
motion-sparing technology and is currently undergoing evaluation in many countries as an alternative
to arthrodesis for the treatment of cervical radiculopathy and myelopathy. The decision whether to use
arthrodesis or arthroplasty is a difficult one. The achievement of good prosthetic performance demands
exacting implantation techniques to ensure correct placement. This fact underlines the increasing importance of special instrumentation and surgical skills that involve an understanding of prosthetic lubrication, wear, and biologic effects and familiarity with currently available information regarding
kinematics, basic science, testing, and early clinical results. Fortunately, a number of devices are at thelate preclinical study stage or at the early clinical trial stage, and results in many cases are promising. In
the near future, it is likely that new designs will be produced to replace spinal discs totally or partiallyin a pathologic entity-specific manner. (doi: 10.2302/kjm.2012-0014-RE) ; Keio J Med 62 (2) : 47–52,
June 2013)

Keywords: cervical total disc replacement, adjacent segment degeneration,sagittal balance,
multilevel, spondylosis

Introduction

which pathological discs are replaced with a mechanicaldevice to preserve joint function.9 Many types of TDR-C
prostheses are at various stages of clinical trials, and several reports have documented their clinical efficacies.10–12
TDR-C is advantageous for maintaining range of motion,
preventing ASD, and promoting normal physiologicalcurvatures.8,13–15 It was initially suggested that TDR-C
could reproduce normal kinematics after implantation,
whereas cervical fusion alters spinal biomechanics andinitiates or accelerates ASD.8,16,17 However, a systemic
review with disappointing results was published by Ce-

For 30 years, anterior cervical discectomy and fusion(ACDF) has been a widely accepted intervention forpatients with cervical radiculopathy or myelopathy unresponsive to conservative treatment. ACDF has beenreported to provide excellent fusion rates and clinicaloutcomes;1–5 however, it reduces the range of neck motion and increases adjacent segment degeneration (ASD)
in the long term.6–8 The past decade witnessed the emergence of cervical total disc replacement (TDR-C), in

Presented at the 1834th Meeting of The Keio Medical Society in Tokyo, June 21, 2012.
Reprint requests to: Seung Hwan Yoon, MD, Department of Neurosurgery, Inha University Hospital, 7-206, 3-Ga Shinheung-dong Jung-gu,
Incheon 400-711, Korea, E-mail: nsyoon@gmail.com
Copyright © 2013 by The Keio Journal of Medicine

47

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poiu-Martin et al. in 2011,18 in which 2 years of follow-up
demonstrated that the effectiveness of TDR-C appeared tobe similar to that of ACDF, and stated that there was only
weak evidence that TDR-C may be superior to fusion fortreating neck and arm pain. Bartels et al., in a meta-analysis, reported that the clinical benefits of TDR-C were
not proven, and recommended that these costly devices
not be used in daily clinical practice.19 Thus, the situation regarding the clinical efficacy and safety of TDR-C
is thoroughly confused. Accordingly, we reviewed newly
reported TDR-C findings from several perspectives, including safety, long-term effectiveness, improvement of
motion at the index level, adjacent segment degeneration, the recovery or maintenance of sagittal balance, thehybrid or multilevel technique, and the use of TDR-C incervical spondylosis. In addition, we include a discussion
on the future direction of TDR-C.
Safety and Effectiveness after Long-term Follow-Up
As mentioned above, Cepoiu-Martin et al. and Bartels
et al. reported disappointing results for TDR-C;18,19 however, many articles endorse the merits of TDR-C. Garrido et al. performed a 48-month follow-up prospective,
randomized, controlled, single-site, comparative study on
the Bryan cervical disc and ACDF.20 Favorable functional outcomes were demonstrated for TDR-C versus fusion,and the incidence of secondary surgery after TDR-C was
lower than that after ACDF. Mummaneni et al. reported
the results of a larger prospective, randomized, multicenter study in which the Prestige Cervical Disc System
was compared with ACDF in patients treated for symptomatic single-level cervical degenerative disease.21 The
improvement in neck disability index score in the TDR-C
group was greater than that in the ACDF control group.
Furthermore, the TDR-C group also had a significantly
lower rate of secondary surgery and supplementary fixation. In contrast, Murrey et al. compared the ProDisc-C
total disc replacement device with ACDF and reported
that clinical outcomes were equally improved after TDRC and after fusion.22 Reoperation, revision, and supplementary fixation rates within the first 24 months werealso significantly lower after TDR-C than after ACDF.
Quan et al. concluded that, 8 years postoperatively, TDRC (Bryan cervical disc arthroplasty) maintains favorable
clinical and radiological results, with preservation of
movement and satisfactory clinical outcomes in the majority of cases,23 whereas Yu et al. found that TDR-C ismore effective than ACDF in terms of overall success andreoperation rates at 24 months in patients with single-level symptomatic cervical disc disease.24 Long-term results
have also shown that TDR-C tends to be more effective insome respects. Coric et al. showed comparable neural decompression and clinical results for TDR-C (Kineflex|C)
and ACDF in a prospective, randomized study.25 In thatstudy, TDR-C was found to be associated with a sig-

Oh CH and Yoon SH: Past, Present, and Future of Cervical Arthroplasty

nificantly higher overall success rate than fusion, while
maintaining motion at the index level. These randomized
controlled trials demonstrate that TDR-C is not inferior
to fusion in terms of long-term safety or effectiveness.
Improvement of Motion at the Index Level
TDR-C may offer other desirable improvements compared with ACDF, including preservation of motion, thepotential to alter the natural history of cervical spondylosis, and the possibility of preventing accelerated degenerative change.26 Many articles have demonstrated
that TDR-C is associated with a significantly better index level range of motion (ROM) than ACDF in the longterm. Auerbach et al. reported that TDR-C increases total cervical ROM more than ACDF does and maintains aphysiologic distribution of ROM throughout the cervicalspine 2 years postoperatively, which potentially lowers
the risk of adjacent segment breakdown compared withthe compensation for loss of motion at the operative level that occurs throughout the unfused cervical spine in
ACDF.27 In a study by Park et al., TDR-C was found topotentially restore and maintain lordotic alignment, discheight, and angular motion, while allowing translation atlevels similar to those present before surgery.28 In contrast, after ACDF, the superior adjacent level was foundto develop increased angular motion compared with thatobserved preoperatively. Zhang et al. and Coric et al. also
reported that TDR-C yielded good clinical results while
maintaining ROM at the index level at 24 months after
surgery.25,29 Barrey et al. concluded that TDR-C generated better biomechanical conditions than ACDF did
at adjacent levels; TDR-C limited the contributions ofthese segments to global ROM and reduced their internal stresses, but only partially restored native kinematics of the cervical spine.30 In addition, Barrey et al.31 in
a 24-month follow-up found that radiological outcomes
after TDR-C (Discocerv) did not fully restore native segmental kinematics and that it caused a significant reduction in flexion–extension and consistent cranial shifts ofthe centers of rotation. Furthermore, the in vivo biomechanical behavior of the prosthesis was found to be very
close to that of good fusion, and lordosis was maintainedat the operated level. Although the merits of TDR-C are
somewhat controversial, it is clear that the technique isbiomechanically and clinically effective in terms of preserving ROM at the index level.
Adjacent Segment Degeneration
The principle rationale for cervical arthroplasty is to reduce the risk of the ASD that occurs after fusion.26 ASD
as a consequence of ACDF has been extensively reported,15,32,33 but it has not been determined if such ASD is
the result of the natural progression of degenerative discdisease, although it is recognized that fusion causes in-Keio J Med 2013; 62 (2): 47–52

creased stress at adjacent levels.6,34 For this reason, TDRC was proposed in an attempt to decrease the incidenceof ASD via motion preservation at both index and adjacent segments.35–37 Many reports show a reduction in theincidence of ASD after TDR-C, but these reports could
be biased by the use of reoperation at an adjacent level
to define ASD.18 Surgeons are less likely to revise TDRC, and patients are less likely to agree to surgery if it isbelieved that the device reduces the incidence of ASD.
Thus, caution should be exercised when interpreting thedata, even though the majority of studies report better
outcomes regarding ASD after TDR-C than after ACDF.
In a report by Garrido et al. on a prospective, randomized,
controlled, single-site trial, ASD (defined by the requirement for adjacent level surgery) was lower in the TDR-C
group (Bryan disc, 5%) than in the ACDF group (12%).20
Furthermore, in a large prospective, randomized, multicenter study conducted by Mummaneni et al. in patientswith symptomatic single-level cervical degenerative disease, the incidence of adjacent segment reoperation was
significantly lower in the TDR-C group.21 In a 12-monthfollow-up study by Park et al, adjacent-level angular motion was unchanged after TDR-C, but angular motion at
the superior adjacent level increased after fusion.28
Recovery or Maintenance of Sagittal Balance
The relation between changes in spinal curvature andclinical outcomes is unclear. Nevertheless, kyphosis after
TDR-C should be avoided to limit axial neck pain andstresses at adjacent levels.31 TDR-C theoretically should
offer motion preservation and the possibility of preventing accelerated degenerative change, and it could aid themaintenance of a natural spinal curvature. However, anearlier report showed increased sagittal kyphosis after
TDR-C (Bryan),38,39 which was probably caused by intraoperative lordotic distraction.38 Functional spine unit
angulation tends toward kyphosis, and in addition, heightis reduced postoperatively because of insufficient anterior column support. Thus, these authors concluded that
TDR-C should be carefully considered when the reconstruction or maintenance of cervical lordosis is desirable.
After these studies were published, many authors reported that sagittal alignment recovered well in the long term,
despite temporary kyphosis. Park et al. reported that cervical lordosis and thoracic kyphosis in their TDR-C groupincreased significantly more than in their ACDF group,8but Sasso et al. reported in a 2-year follow-up study withlevel I evidence that overall cervical sagittal alignment
was no different in experimental and control populations.40 Anakwenze et al. reported an increase in operated level (+3°) and C2–C6 lordosis (+3.1°) after TDR-C(ProDiscC) implantation in a level I evidence study involving 180 patients,30,41 and, in a prospective study, consistently increased cervical lordosis after TDR-C (Discocerv) was also observed by Barrey et al.30 Kyphosis could49

occur after TDR-C as a result of too great a disc insertion
angle and overmilling, and some authors have described
techniques to help avoid these problems, such as changing the insertion angle42–45 and depth.45 Interestingly, in
one of these reports, not one of 29 patients undergoing amodified TDR-C procedure (Bryan) developed kyphosisof the functional spine unit in the neutral position44.
Hybrid Technique for Multilevel Surgery and TDR-C
in Cervical Spondylosis
The hybrid technique involving arthrodesis and TDRC has a biomechanical advantage over two-level fusion in terms of reducing adjacent level hypermobility.
There has been some debate regarding the usefulnessof the hybrid technique in patients that have previously
undergone fusion or in patients with multi-level cervicaldisease or cervical spondylosis. In vitro30 investigations
and spinal structure models46 have shown better biomechanical conditions at adjacent levels after TDR-C thanafter ACDF and that TDR-C limits contributions of thesesegments to global ROM and reduces the amount of internal stresses. Clinical reports by Lee et al. and Martin
et al. also showed biomechanical advantages for the hybrid technique in terms of reducing adjacent-level hypermobility and increasing moment loads without causing
impingement of the prosthesis end plate.47,48 Several versions of the hybrid technique are available, as describedby Cardoso et al.49 Personally, I prefer the technique thatuses TDR-C at the level of a well-preserved disc space,
but ACDF in regions of larger motion. Multilevel cervical arthroplasty with TDR-C (Prestige ST) was reported
by Cardoso et al. to be a safe and effective alternative
to fusion for the management of cervical radiculopathy
and myelopathy.50In that study, the technique for inserting TDR-C during contiguous multilevel cervical discarthroplasty (which was presented as an alternative to
multilevel arthrodesis) was described in 10 patients withradiculopathy and myelopathy; a similar technique wasreported by Sekhon.51 The hybrid technique with multilevel TDR-C was also reported with level II evidence byHuppert et al.52 They found no major significant clinical differences between single- and multi-level TDR-C(Mobi-C).
Surgical indications for TDR-C were found to be extendable to cervical spondylosis,9,49–51 defined as thepresence of bridging osteophytes, loss of disc height of>50%, absence of motion (<2°), and a narrow spinal canal(<12 mm). However, some surgeons opposed to TDR-C
in spondylosis have suggested that even TDR insertion
could not be expected to achieve motion preservation
when hard spurs or uncinate process-to-facet fusion ispresent.53,54 Thus, others have recommended some techniques to overcome increased motion even in spondylosis, such as posterior longitudinal ligament resection withventral foraminotomy53 and/or bilateral uncinatectomy.54

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Oh CH and Yoon SH: Past, Present, and Future of Cervical Arthroplasty

Fig. 1 Serial surgical procedure for cervical disc replacement with an artificial disc.
(A,B) The cartilaginous endplate was removed without damaging the bony end plate at the C4/5 level. (C) As part of the cervical arthroplasty procedure, an artificial disc (Mobi-C; LDR Medical, Troyes, France) was inserted. This disc prosthesis is a three-piece, biarticulating, metal-on-polyethylene, semiconstrained device that consists of two metal base plates with an ultra-high molecular weight
polyethylene insert. This insert is claimed by the manufacturer to be based on a mobile-bearing technology that improves ROM. Twolateral stops on the inferior endplate limit movement of the insert.

Future Perspectives
Many questions about TDR-C remain unanswered,26
such as those concerning debris produced by devices,
subsidence, and the long-term rate of adjacent segmentdegeneration after disc replacement. Arthroplasty seems
to be as safe as ACDF, which justifies its use in the shortterm, but it may become a substitute for fusion in the
future.26 However, the question as to whether TDR-C
reduces the incidence of adjacent segment degeneration
remains unanswered. Nevertheless, it would seem reasonable to continue with disc replacements in selectedpatients to determine long-term results and indications.
There is no role for the indiscriminate use of arthroplasty,
which should not be considered simply as a successor or
replacement for fusion. Quality of life and cost effectiveness also need to be assessed in the long term, especiallygiven the pressures caused by increasing costs that affectevery healthcare system today. Solid long-term data areneeded before we can fully appraise the role of arthroplasty, and we therefore need to ensure that the momentum to follow-up this group of patients is maintained. In
fact, the present standard of treatment may be flawed, but
we will only really know where arthroplasty stands if thespirit of research is sustained.26

Surgical Steps of TDR-C Using
the Mobi-C Prosthesis
A standard Smith-Robinson approach was used to expose the treatment levels. The cartilaginous end plate
was removed with a curette taking care not to damage
the bony end plate. The uncovertebral joints were left intact. An artificial disc (Mobi-C; LDR Medical, Troyes,
France) was used for cervical arthroplasty (Fig. 1). This
disc prosthesis is a three-piece, biarticulating, metal-onpolyethylene, semiconstrained device consisting of two
metal base plates with an ultra-high molecular weight
polyethylene insert. Two lateral stops on the inferior end
plate limit movement of the insert. This artificial disc hasreceived approval from the Food and Drug Administration to undergo an investigational device exemption trial
in the United States.
Conclusions
This study reviews recent articles on TDR-C and presents multiple perspectives. The long-term safety, effectiveness, and preservation of motion at the index level of
TDR-C are well supported by evidence, but the recovery
and maintenance of sagittal balance are similar to thoseKeio J Med 2013; 62 (2): 47–52

for conventional fusion. Although sufficient evidence is
not yet available, the hybrid multilevel technique and thebroad application to cervical spondylosis are also possible. There is no reason to be hesitant about considering
the use of TDR-C.
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