Article

Review Article

The Role of Anterior Cervical Discectomy and Fusion on Relieving Axial Neck Pain in Patients With Single-Level Disease: A Systematic Review and Meta-Analysis

Colby Oitment, MD 1 , Tracy Watson, PA

1 , Victor Lam, MD

2 ,

Mohammed Aref, MD 1 , Alex Koziarz, MSc

1,3 , Edward Kachur, MD

1 ,

Jetan H. Badhiwala, MD 3 , Saleh A. Almenawer, MD

1 ,

and Aleksa Cenic, MD 1

Abstract

Study Design: Systematic review and meta-analysis.

Objectives: This study aims to evaluate the effects of anterior cervical decompression and fusion (ACDF) on axial neck pain in adult patients receiving surgery for myelopathy, radiculopathy, or a combination of both.

Methods: Two independent reviewers completed a librarian-assisted search of 4 databases. Visual Analogue Scale (VAS) and Neck Disability Index (NDI) scores were extracted preoperatively and at 3, 6, 12, 24, 36, 48, and 48+ months postoperatively for ACDF groups and pooled using a random-effects model.

Results: Of 17 850 eligible studies, 37 were included for analysis, totaling 2138 patients analyzed with VAS and 2477 with NDI score. Individual VAS mean differences were reduced at 6 weeks (�2.5 [95% confidence interval (CI): �3.5 to �1.6]), 3 months (�2.9 [�3.7 to �2.2]), 6 months (�3.2 [�3.9 to �2.6]), 12 months (�3.7 [�4.3 to �3.1]), 24 months (�4.0 [�4.4 to �3.5]), 48 months (�4.6 [�5.5 to �3.8]), and >48 months (�4.7 [�5.8 to �3.6]) follow-up (P < .0001 for all endpoints). Individual NDI mean differences were reduced at 6 weeks (�26.7 [�30.9 to �22.6]), 3 months (�29.8 [�32.7 to �26.8]), 6 months (�31.2 [�35.5 to �26.8)], 12 months (�29.3 [�33.2 to �25.4]), 24 months (�28.9 [�32.6 to �25.2]), 48 months (�33.1 [�37.4 to �28.7]), and >48 months (�37.6 [�45.9 to �29.3]) follow-up (P < .0001 for all endpoints). Conclusions: ACDF is associated with a significant reduction in axial neck pain compared with preoperative values in patients being treated specifically for myelopathy or radiculopathy. This influences the preoperative discussions surgeons may have with patients regarding their expectations for surgery. The effects seen are stable over time and represent a clinically significant reduction in axial neck pain.

Keywords ACDF, anterior cervical decompression and fusion, axial neck pain, Visual Analogue Scale, Neck Disability Index

Introduction

Degenerative cervical disc disease may result in disc hernia-

tions, which compress nerve roots causing radiculopathy or

compress the spinal cord causing myelopathy. 1

Patients with

degenerative cervical disc disease classically have a significant

degree of axial neck pain. 1

The source of axial neck pain,

whether it be discogenic, osseous, muscular, or alignment

related, is generally difficult to elucidate on history and

1 McMaster University, Hamilton, Ontario, Canada

2 University of Western Ontario, London, Ontario, Canada

3 University of Toronto, Toronto, Ontario, Canada

Corresponding Author:

Aleksa Cenic, Division of Neurosurgery, Hamilton Health Sciences, 237 Barton

St E, Hamilton, Ontario L8L 2X2, Canada.

Email: [email protected]

Global Spine Journal 2020, Vol. 10(3) 312-323

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physical examination. For this reason, surgeons rely on neuro-

logical signs and symptoms to guide treatment.

Anterior cervical discectomy and fusion (ACDF) is a

procedure that may be performed for patients with degen-

erative spondylitic myelopathy or radiculopathy. While the

specific indications for surgery vary depending on patient

symptoms and anatomic considerations such as previous

surgery or deformity, there are well-recognized guidelines

for treatment. 1

Myelopathy guidelines generally recom-

mend decompression for moderate or severe patient symp-

toms, and the literature suggests surgical decompression

for radiculopathy when it is unresponsive to a minimum

of 6 weeks of conservative therapy or symptoms are pro-

gressive. 1

Accurate patient understanding of the expected

surgical outcomes may improve the perceived success of

the surgery and reduce medicolegal litigation. 12

This

involves accurately addressing both patient and surgeon

expectations of the procedure preoperatively. While mye-

lopathy may improve with surgery, the results are variable

so the general goals of the procedure are to halt progres-

sion. 15,16

Radiculopathy, however, tends to improve more

reliably so patients anticipate reliable reductions in arm

pain. 2,3

While axial neck pain symptoms are particularly troubling

to many patients, the effects of ACDF on axial neck pain are

more poorly understood. Whereas several studies report a

reduction in axial neck pain following ACDF, there have been

no meta-analyses to date examining the effects of ACDF on

cervical spondylitic myelopathy and/or radiculopathy.

Accordingly, preoperative discussions may lack clarity

regarding the outcomes of surgery with regard to the prog-

nosis of axial neck pain. Therefore, the purpose of this meta-

analysis is to examine all randomized controlled trials and

prospective cohort studies that recorded preoperative and

postoperative axial neck pain scores in order to examine theFigure 1. Flow diagram of search strategy with included studies.

Table 1. A List of Studies Included in the Analyses.

Study Year VAS NDI Study Year VAS NDI

Zoëga et al Group 14 1998 X Maldonado et al22 2011 X X Zoëga et al Group 24 1998 X Zhang et al23 2012 X X Porchet et al 20 045 2004 X X Coric et al24 2013 X X Chen et al6 2005 X Ha et al Group 125 2013 X X Schils et al Group 17 2006 X Ha et al Group 225 2013 X X Schils et al Group 27 2006 X Chen et al26 2013 X X Bindal et al

8 2007 X Kasliwal et al Group 1

27 2013 X X

Mummaneni et al9 2007 X Kasliwal et al Group 227 2013 X X Nabhan et al

10 2007 X Kasliwal et al Group 3

27 2013 X X

Oktenoglu et al11 2007 X Phillips et al28 2013 X X Cosar et al

12 2008 X Zigler et al

29 2013 X X

Fernández-Fairen et al Group 113 2008 X X Janssen et al30 2015 X Fernández-Fairen et al Group 2

13 2008 X X Skeppholm et al

31 2015 X X

Bhadra et al Group 114 2009 X Arnold et al Group 132 2016 X X Bhadra et al Group 2

14 2009 X Arnold et al Group 2

32 2016 X X

Bhadra et al Group 314 2009 X Hisey et al33 2016 X X Heller et al

15 2009 X Loumeau et al

34 2016 X X

Murrey et al16 2009 X Richter et al35 2016 X Nabhan et al Group 1

17 2009 X X Burkus et al

36 2017

Nabhan et al Group 217 2009 X X Pandey et al37 2017 X X Burkus et al

18 2010 X X Razankovic et al

38 2017 X

Delamarter et al19 2010 X X Sasso et al 201 739 2017 X X Garrido et al

20 2010 X X Arts et al Group 1

40 2017 X

Löfgren et al Group 121 2010 X X Arts et al Group 240 2017 X Löfgren et al Group 221 2010 X X

Abbreviations: VAS, Visual Analogue Scale; NDI, Neck Disability Index.

Oitment et al 313

effect of single-level ACDF on axial neck pain in patients

with myelopathy and/or radiculopathy.

Methods

Eligibility Criteria

This systematic review included adult patients receiving

ACDF. The inclusion criteria for this review were the follow-

ing: (1) published online and in the English language; (2) ran-

domized controlled trial or cohort study; (3) included

preoperative and postoperative data on subjective midline axial

neck pain scores (either Visual Analog Scale [VAS] or Neck

Disability Index [NDI] scores); (4) single-level pathology. All

studies involving corpectomy or multilevel anterior decom-

pressions, as well as posterior decompressive procedures, were

excluded. In multiple cases there were studies published with

what, in the authors’ best judgement, appeared to be the same

ACDF data as a previously published control arm for disc

arthroplasty versus ACDF trials. In these cases, the most recent

data was utilized and the earlier studies by these authors were

not included.

Table 2. A List of Studies Included Along With Respective MINORS Scores for Quality Assessment.

Study MINORS

Score Study MINORS

Score

Zoëga et al4 15 Zhang et al23 20 Porchet et al5 20 Coric et al24 22 Chen et al6 21 Ha et al25 21 Schils et al7 19 Chen et al26 20 Bindal et al8 14 Kasliwal et al27 22 Mummaneni et al9 21 Phillips et al28 21 Nabhan et al10 22 Zigler et al29 22 Oktenoglu et al

11 13 Janssen et al

30 21

Cosar et al12 19 Skeppholm et al31 20 Fernández-Fairen et al

13 22 Arnold et al

32 22

Bhadra et al14 18 Hisey et al33 18 Heller et al

15 20 Loumeau et al

34 20

Murrey et al16 20 Richter et al35 20 Nabhan et al

17 20 Burkus et al

36 19

Burkus et al18 22 Pandey et al37 18 Delamarter et al

19 23 Razankovic et al

38 20

Garrido et al20 21 Sasso et al39 19 Löfgren et al

21 23 Arts et al

40 18

Maldonado et al22 21 Mean + SD 19.9 + 2.2

Abbreviation: MINORS, Methodological Index for Non-Randomized Studies.

Figure 2. VAS baseline scores compared to 3-month follow-up (�2.94 [95% CI: �3.67 to �2.21]; heterogeneity: I2 ¼ 99.7%, P < .001).

314 Global Spine Journal 10(3)

Search Strategy

Two independent authors searched MEDLINE, EMBASE,

PubMed, and Cochrane databases with the guidance of a profes-

sional librarian using the following terms: “anterior cervical

decompression and fusion” OR “ACDF,” OR “cervical decom-

pression” AND “axial neck pain” OR “midline neck pain” to

broaden the number of studies retrieved. Initial search results were

vetted for duplicates and a title screen was performed for relevance.

Reference lists of eligible studies were screened for additional

studies meeting eligibility criteria. Discrepancy was resolved with

discussion and consultation with the senior supervising author.

Risk of Bias

The risk of bias of included studies was assessed by using the

Methodological Index for Non-Randomized Studies (MIN-

ORS) scale. The MINORS scale scores vary from 0 to 24 for

risk of bias. The use of this scale is appropriate because the

randomization process of the trials did not apply to this review

as only data from the ACDF trial arms were extracted.

Data Abstraction

Two independent reviewers collected data into Excel spread-

sheets. Demographics, type and study risk of bias, mean

preoperative and postoperative VAS and/or NDI scores were

recorded at multiple points in time (preoperatively, and post-

operatively at 6 weeks, 3, 6, 12, 24, 36, and 48 months).

Research ethics board approval is not required as it examines

data from published studies. Therefore, there are no concerns

regarding patient privacy or participant ethics.

Statistical Analysis

Demographic data is pooled for age, gender, smoking status,

and NDI and VAS scores. The pooled proportions and pooled

mean with standard deviation are reported. Some studies uti-

lized a 100-point VAS neck pain scale while others utilized the

more traditional 10-point scale. These scores are documented

in the tables as reported by authors; however, the 10-point scale

was selected for formal analyses and the 100-point scores were

therefore divided by 10 to standardize the pain score from 0 and

10. In order to evaluate the mean change in pain scores, the

mean pain scores from the preoperative assessment and at each

follow-up visit were pooled from 32 included studies. The

pooled means were compared to preoperative pooled means

at each follow-up visit by use of a random-effects model with

inverse variance. Between-study heterogeneity was tested

using w2 test and quantified by I2 statistics. The overall pooled mean change in pain scores with 95% confidence intervals

Figure 3. VAS baseline scores compared to 6-month follow-up (�3.21 [95% CI: �3.85 to �2.56]; heterogeneity: I2 ¼ 99.5%, P < .001).

Oitment et al 315

(CIs) over 24 months and heterogeneity are reported. Compre-

hensive Meta-Analysis version 3.3.070 (Biostat, Inc, Engle-

wood, NJ) was used for meta-analysis.

Results

Initial librarian-assisted search revealed 17 850 studies, which

after deletion of duplicates and initial title screen for relevance

left 3740 studies for abstract review (Figure 1). Following

abstract review, 3375 studies were removed for failure to meet

eligibility criteria. The remaining 365 studies were examined

via full text review. Discrepancies were resolved between

authors and 37 studies were included in final analyses. 4-40

Indi-

vidual studies are presented in Table 1. Detailed information

regarding studies and collected data is available in the appen-

dix, available online.

Studies range in year from 1998 to 2017. A total of 2138

patients are analyzed with regard to VAS scores and 2477

patients with regard to NDI scores. Fifty-three percent of par-

ticipants were male. Average time to final follow-up ranged

from 6 months to 120 months for VAS (mean 33.1 + 23.9 months) and NDI data (mean 34.5 + 23.8 months).

Risk of Bias

Each of the 37 studies underwent risk of bias by MINORS

scale. The mean MINORS score was 19.9 (+2.2) and ranged from 13 to 23 indicating that the risk of bias was overall accep-

table for most of the included studies. Table 2 presents each

study along with its MINORS score.

Axial Neck Pain

At every time point there was a statistically significant decrease

in both VAS and NDI scores. Individual VAS mean differences

are reduced compared postoperative scores at 6 weeks, 3

months, 6 months, 12 months, 24 months, 48 months, and

>48 months follow-up were �2.52 (95% CI: �3.46 to �1.59; P < .0001; I

2 ¼ 99.9%; Figure A1), �2.94 (95% CI: �3.67 to �2.21; P < .0001; I2 ¼ 99.7%; Figure 2), �3.21 (95% CI: �3.85 to �2.56; P < .0001; I2 ¼ 99.5%; Figure 3), �3.68 (95% CI: �4.26 to �3.10; P < .0001; I2 ¼ 98%; Figure 4), �3.96 (95% CI: �4.40 to �3.53; P < .0001; 94.7%; Figure 5), �4.65 (95% CI: �5.51 to �3.79; P < .0001; 90.9%; Figure 6), �4.71 (95% CI: �5.83 to �3.58; P < .0001; I2 ¼ 93.0%; Figure A2), respectively.

Figure 4. VAS baseline scores compared to 12-month follow-up (�3.68 [95% CI: �4.26 to �3.10]; heterogeneity: I2 ¼ 98.1%, P < .001).

316 Global Spine Journal 10(3)

Figure 5. VAS baseline scores compared to 24-month follow-up (�3.96 [95% CI: �4.40 to �3.53]; heterogeneity: I2 ¼ 94.7%, P < .001).

Figure 6. VAS baseline scores compared to 48-month follow-up (�4.65 [95% CI: �5.51 to �3.79]; heterogeneity: I2 ¼ 90.9%, P < .001).

Oitment et al 317

Figure 7. NDI baseline scores compared to 3-month follow-up (�29.76 [95% CI: �32.71 to �26.81]; heterogeneity: I2 ¼ 96.0%, P < .001).

Figure 8. NDI baseline scores compared to 6-month follow-up (�31.17 [95% CI: �35.49 to �26.84]; heterogeneity: I2 ¼ 98.1%, P < .001).

318 Global Spine Journal 10(3)

Individual NDI mean differences at 6 weeks, 3 months, 6

months, 12 months, 24 months, 48 months, and >48 months

follow-up were �26.73 (95% CI: �30.88 to �22.59; P < .0001; I

2 ¼ 97.0%; Figure A3), �29.76 (95% CI: �32.71 to �26.81; P < .0001; I2 ¼ 96.0%; Figure 7), �31.17 (95% CI: �35.49 to �26.84; P < .0001; I2 ¼ 98.1%; Figure 8), �29.31 (95% CI: �33.18 to �25.43; P < .0001; I2 ¼ 93.0%; Figure 9), �28.90 (95% CI: �32.64 to �25.16; P < .0001; I 2 ¼ 96.1%; Figure 10), �33.09 (95% CI: �37.43 to �28.74;

P < .0001; I 2 ¼ 86.3%; Figure 11), and �37.61 (95% CI:

�45.88 to �29.34; P < .0001; I2 ¼ 91.0%; Figure A4), respectively.

Discussion

Axial neck pain is a multifactorial problem associated with

muscular, ligamentous, discogenic, and degenerative bony

spinal anatomy. This meta-analysis demonstrates that in

patients with myelopathy or radiculopathy resulting from

single-level disc disease, there are consistent reductions in

axial neck pain following ACDF. It is likely that the disc itself

is the main neck pain generator in these patients as pain is

relieved following discectomy and fusion, and motion-

preserving disc arthroplasty. For ACDF, the effect is stable

over time with similar mean reductions in VAS and NDI at all

time points postoperatively. These results will help guide pre-

operative discussions with patients, and may accurately address

patient expectations.

Minimally important differences (MIDs) are the smallest

effects that a patient would consider beneficial to justify a

procedure 41

and have been studied for multiple different

scales within the field of spinal surgery. The MID for the VAS

is found to be 2.5 points for extremity, 42

and 3.5 points for

VAS axial pain. 42

The MID for NDI is determined to be 7.5

points. 43

While the NDI data suggest a clinically significant

reduction in axial neck pain at all time points, the VAS data

presented here exceed the MID 12 months following ACDF.

Our study finds a 28.8-point decrease in NDI at 24 months as

well as a 4.1-point decrease in VAS for neck pain. The precise

estimates and large number of included studies suggest a

comprehensive evaluation of the current evidence of ACDF

on the outcome of neck pain.

While this study reports clinically meaningful and statisti-

cally significant reductions in neck pain following ACDF, we

do not recommend ACDF for neck pain in the absence of

currently accepted indications for surgery. Selection bias is

present as included patients were enrolled due to the presence

of cervical myelopathy or radiculopathy. Accordingly, inter-

preting a causal relationship between ACDF and neck pain in

the absence of neural compression warrants caution. One group

Figure 9. NDI baseline scores compared to 12-month follow-up (�29.31 [95% CI: �33.18 to �25.43]; heterogeneity: I2 ¼ 93.0%, P < .001).

Oitment et al 319

of surgeons from Washington University report a systematic

review on 3 case series utilizing ACDF for the purpose of

mechanical/axial neck pain in patients without radiculopathy

or any other standard indications for the procedure. They were

criticized by editorial staff for presenting limited data to pro-

duce a meaningful analysis; however, they are commended for

venturing beyond the accepted standards for this procedure.

The 3 studies they reported 44-46

included a total of 166 patients

Figure 10. NDI baseline scores compared to 24-month follow-up (�28.90 [95% CI: �32.64 to �25.16]; heterogeneity: I2 ¼ 96.12%, P < .001).

Figure 11. NDI baseline scores compared to 48-month follow-up (�33.09 [95% CI: �37.43 to �28.74]; heterogeneity: I2 ¼ 86.3%, P < .001).

320 Global Spine Journal 10(3)

showing a 50% to 60% decrease in axial neck pain at 4-year follow-up and patient satisfaction rates ranging from 56% to 79%.3 Functional outcomes were improved between 32% and 52% from baseline.3

Future research may attempt to understand the direct rela-

tionship between ACDF and axial neck pain in patients with

single-level disc disease. It is unethical to randomize patients to

surgical treatment for neck pain, as ACDF is not accepted as a

treatment for this condition. However, the current treatment

guidelines for myelopathy suggest that mild myelopathy may

be treated conservatively or surgically. Therefore, clinical

equipoise exists to design a study examining patients with mild

myelopathy, with and without axial neck pain, to determine the

treatment effects of ACDF on axial neck pain directly. The

degree to which axial neck pain is affected by other treatments

for myelopathy (eg, laminectomy, laminoplasty, anterior cor-

pectomy, and fusion) remains to be determined. It would be

useful for future research to fully characterize the effects of

these procedures on axial neck pain.

There are multiple strengths in this meta-analysis. A thorough

search strategy is used with various keywords and a comprehen-

sive search of multiple databases is undertaken. There are multi-

ple reviewers involved in the process of article retrieval, risk of

bias assessment, and data abstraction to ensure accuracy and

minimize bias. The included studies are multicenter trials, includ-

ing multiple implant products and surgeons, which increases the

generalizability of our results. While we demonstrate high levels

of heterogeneity in our outcomes at several time points, a large

majority of studies were in favor for ACDF for a reduction in axial

neck pain. Accordingly, we do not consider this inconsistency in

treatment effect to weaken our study’s conclusion.

Conclusions

Our results indicate that ACDF is associated with a significant

reduction in axial neck pain compared to preoperative values in

patients being treated for myelopathy or radiculopathy. These

effects meet clinically significant MIDs and may influence

patients’ expectations for surgery. These results may help clar-

ify expected surgical outcomes in preoperative discussions.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to

the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, author-

ship, and/or publication of this article.

Supplemental Material

The supplemental material is available in the online version of the

article.

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