Long-Term Outcomes of Cervical Disc Replacement and Anterior Cervical Discectomy and Fusion: A Review of FDA IDE Trials With Real-World Comparison

Abstract

Study design

Retrospective comparative cohort study.

Objective

To validate FDA IDE–sponsored trial findings on cervical disc replacement (CDR) and anterior cervical discectomy and fusion (ACDF) by comparing reoperation outcomes with real-world data.

Methods

Patients undergoing one- or two-level ACDF or CDR from 2010-2022 were identified in the PearlDiver (PD) database. FDA IDE trials were retrieved through review of databases. Subsequent surgeries and sample sizes were extracted at 2-, 4-, 5-, 7-, and 10-year intervals. Event rates were calculated as reoperations divided by patients at risk, and survival probabilities as S(t) = 1−event rate. Kaplan–Meier–style survival curves were reconstructed using the Guyot algorithm with a monotonicity constraint. Pooled FDA survival probabilities were weighted by number at risk. Hazard ratios (HRs) were derived from log-transformed survival probabilities, and statistical significance was tested using Pearson’s chi-square or Fisher’s exact test. Analyses were stratified by surgical level (1- vs 2-level) and procedure type (CDR vs ACDF).

Results

In total, 277 146 ACDF and 25 957 CDR patients from PD and 46 FDA trials were analyzed. CDR reoperation risks were similar between FDA and PD cohorts, though differences were significant at 2-, 7-, and 10-year follow-up for 1-level procedures. ACDF reoperation risks were consistently and significantly lower in PD (eg, HR 0.4 at 7 years).

Conclusion

Reoperation risks for CDR were broadly comparable, while ACDF outcomes were superior in practice compared with trials. These differences may reflect trial selection bias or stricter adjudication of ACDF outcomes. Validation against real-world data supports long-term safety assessment and personalized surgical decision-making.

Introduction

Degenerative cervical spine disease is a common disorder characterized by neck pain, radiculopathy, and myelopathy. ¹ Early surgical treatment involved laminectomy and posterior forminotomy, however, due to anatomical limitations in effectively addressing centrally or paracentrally located discs, anterior cervical discectomy and fusion (ACDF) emerged as the favorable method by the mid-20^th century. ² ACDF is now regarded as the gold standard for degenerative cervical disc disease. ³

To address the limitations of ACDF, particularly reduced spinal mobility and adjacent segment disease (ASD), cervical disc replacement (CDR) was developed as a motion-preserving alternative. Since its commercial debut in 2007, ⁴ CDR use has grown significantly.^5-8 Currently, 9 devices are approved for single-level CDR, with 3 also approved for two-level procedures.^4,9-17 Clinical trials have shown CDR to be non-inferior to ACDF, with better long-term outcomes in pain relief, function, and lower rates of ASD and revision surgery.

CDR approvals were based on FDA investigational device exemption (IDE) trials, which were non-blinded, multicenter randomized controlled trials. ¹⁸ However, concerns have been raised about the rigour of these studies due to limitations in design, bias, and post-approval oversight.^19,20 Although post-approval studies (PAS) are required, ¹⁸ they often suffer from small sample sizes, poor follow-up, and limited generalizability. ²¹

Given these limitations, this study aims to validate the findings of FDA IDE-sponsored trials by comparing long-term outcomes of CDR and ACDF using real-world data from a national database. Specifically, this study will assess subsequent surgery rates reported in the FDA trials and compare them to those observed in a large, nationally representative cohort over the last decade.

Methods

Data Source and Study Population

This study utilized the PearlDiver (PD) Mariner Database (PearlDiver Technologies, Colorado Springs, CO, USA) to identify patients who underwent ACDF and CDR between 2010 and 2022. The PD database is a nationwide insurance claims database containing approximately 157 million de-identified patients, that includes demographic, diagnostic, and procedural data from various payer types across inpatient and outpatient settings. As the study relied on anonymized data, already published articles and was retrospective in nature, informed consent was waived, and institutional review board approval was not required.

Pubmed, Scopus and Cochrane databases were used to identify FDA-approved IDE trials on April 14, 2025.

Identification of Study Cohorts in PearlDiver

International Classification of Diseases (ICD), 9th (ICD-9) and 10th (ICD-10) editions, along with Current Procedural Terminology (CPT) codes, were utilized to identify patients (Supplemental Table 1). Specifically, patient records containing codes for one- or two-level ACDF and CDR procedures were queried. To exclude hybrid surgical constructs, patients in the ACDF group were removed if they had undergone CDR within 1 week of the index procedure. Similarly, patients in the CDR group were excluded if they had undergone ACDF within 1 week of the procedure. Patients in both study cohorts were also excluded if they had a history of prior cervical surgery before the index ACDF or CDR procedure. Additional exclusion criteria included patients under 18 years of age, those with less than 1 year of postoperative follow-up, and cases involving surgical indications related to trauma, malignancy, or infection. Patients were further categorized based on subsequent surgeries performed in the cervical region.

To simulate an intention-to-treat analysis similar to FDA IDE trials, only patients with complete follow-up data were included. For example, in the 2-year cohort, patients were included if their index surgery occurred between 2010 and 2020, as PD contains data through 2022, ensuring all patients could have full follow-up. Similarly, patients in the 3-year cohort were included if their index surgery occurred between 2010 and 2019; for the 4-year cohort, between 2010 and 2018; for the 5-year cohort, between 2010 and 2017; for the 7-year cohort, between 2010 and 2015; and for the 10-year cohort, between 2010 and 2012.

Identification of Study Cohorts in FDA IDE Trials

Pubmed, Scopus and Cochrane databases were queried since inception on April 14, 2025, using human participants and the English language as a search filter and (“Anterior Cervical Discectomy and Fusion” OR “ACDF” OR “Cervical Discectomy” OR “Fusion” OR “Cervical Spine Fusion” OR “Cervical Degenerative Disease” OR “Cervical Degeneration”) AND (“Cervical Disc Replacement” OR “CDR” OR “Cervical Total Disc Replacement” OR “CTDR” OR “Total Disc Replacement” OR “TDR” OR “Artificial Disc Replacement” OR “Cervical Arthroplasty” OR “Disc Arthroplasty” OR “Cervical Degenerative Disease” OR “Cervical Degeneration”) AND (“Randomized Controlled Trial” OR “RCT” OR “Randomized Study” OR “Clinical Trial” OR “Interventional Study”) as a search strategy. Our exclusion criteria included trials that compared devices not approved by the FDA for commercial distribution or that reported subsequent surgery rates beyond a 10-year follow-up period due to the small sample size available for comparison in the PD database. Duplicates were removed, and relevant full-text randomized controlled clinical trials (RCT) were screened for data collection following the title and abstract screening (Figure 1).

Figure 1.

Flow Chart for the Selection of FDA IDE Trials

Primary Endpoints

The primary aim of this study was to evaluate whether the outcomes, in terms of subsequent surgery required at the cervical region, reported across FDA IDE trials align with real-world outcomes (Table 1).

Table 1.

Subsequent Surgery Event In PearlDiver And FDA IDE Trials Cohort.

F/up period a	Cohort a	PD total patients	PD (n (%))	FDA trials total patients b	FDA trials (n (%)) b	I2c
2-year	1-Level CDR	18 879	588 [3.11%]	3013	127 [4.22%]	88.7%
	Z-statistic	−3.029	−3.029
	2-Level CDR	3057	105 [3.43%]	825	33 [4.0%]	1.3%
	Z-statistic	−0.749	−0.749
	1-Level ACDF	156 501	6129 [3.91%]	2696	199 [7.38%]	48.5%
	Z-statistic	−8.473	−8.473
	2-Level ACDF	90 717	4005 [4.41%]	643	69 [10.73%]	0%
	Z-statistic	−6.915	−6.915
3-year	2-Level CDR	2387	93 [4.1%]	234	7 [3%]	-
	Z-statistic	0.823	0.823
	2-Level ACDF	81 532	4393 [5.4%]	105	14 [13.3%]	-
	Z-statistic	−3.152	−3.152
4-year	1-Level CDR	13 616	626 [4.6%]	530	30 [5.66%]	59.1%
	Z-statistic	−1.081	−1.081
	2-Level CDR	1673	87 [5.31%]	225	9 [4.0%]	-
	Z-statistic	0.734	0.734
	1-Level ACDF	125 474	6970 [5.55%]	434	49 [11.29%]	0%
	Z-statistic	−4.661	−4.661
	2-Level ACDF	70 627	4420 [6.26%]	105	16 [15.24%]	-
	Z-statistic	−3.272	−3.272
5-year	1-Level CDR	11 128	568 [5.10%]	1769	116 [6.56%]	69.4%
	Z-statistic	−2.380	−2.380
	2-Level CDR	1038	52 [5.76%]	459	33 [7.19%]	0%
	Z-statistic	−1.571	−1.571
	1-Level ACDF	111 007	6839 [6.16%]	1528	189 [12.37%]	68.2%
	Z-statistic	−8.856	−8.856
	2-Level ACDF	61 445	4278 [6.96%]	210	44 [20.95%]	0%
	Z-statistic	−6.469	−6.469
7-year	1-Level CDR	6848	420 [6.13%]	2023	235 [10.72%]	96.4%
	Z-statistic	−6.371	−6.371
	2-Level CDR	201	11 [8.96%]	868	70 [8.06%]	60%
	Z-statistic	−1.160	−1.160
	1-Level ACDF	80 735	5848 [7.24%]	1679	329 [18.04%]	23%
	Z-statistic	−14.066	−14.066
	2-Level ACDF	42 919	3493 [8.17%]	586	119 [20.31%]	71.5%
	Z-statistic	−8.776	−8.776
10-year	1-Level CDR	2190	153 [6.99%]	1028	92 [8.95%]	85.9%
	Z-statistic	−1.798	−1.798
	2-Level CDR	Small sample	-	209	25 [11.9%]	-
	1-Level ACDF	30 592	2569 [8.39%]	953	199 [20.88%]	93.4%
	Z-statistic	−11.066	−11.066
	2-Level ACDF	Small sample	-	188	51 [27.1%]	-

^aSome patients had more than 1 surgical procedure.

^bPooled subsequent surgery rate across FDA trials was compared with PD data.

^cRepresent heterogeneity across FDA trials.

Abbreviations: F/up = Follow-up period; FDA = Food and Drug Administration; PD = PearlDiver; n = number of events.

Statistical Analysis

All statistical analyses were performed using R (version 3.4.4). For each included FDA IDE trial and Pearl Diver (PD) cohort, the number of subsequent surgeries and total sample size were extracted at each reported follow-up interval (2, 4, 5, 7, and 10 years). Event rates were calculated as the number of subsequent surgeries divided by the number of patients at risk at that time point. Survival probabilities were then derived as S(t) = 1−event rate.

To generate Kaplan–Meier–style survival curves from aggregate data, patient-level event times were reconstructed from the published discrete survival probabilities using the algorithm described by Guyot et al (2012) ²² for individual patient data (IPD) reconstruction from published Kaplan–Meier curves. In cases where reported survival probabilities showed non-monotonic trends (ie, survival increasing over time), a monotonicity constraint was applied by replacing each value with the cumulative minimum of all preceding survival probabilities. This ensured biologically plausible curves and addressed potential artefacts arising from small sample sizes or reporting variability. For each surgical level (1-level, 2-level) and procedure type (CDR, ACDF), pooled FDA survival probabilities were calculated as weighted means, with weights proportional to the number at risk in each trial.

For comparative analyses, hazard ratios at each follow-up interval were calculated from survival probabilities using the formula: HR (t) = −log SPD (t)/−log SFDA(t). While these values do not represent Cox regression–derived hazard ratios, they provide a consistent relative measure of survival differences between FDA and PD cohorts at discrete time points. Statistical significance of differences in event rates between FDA and PD cohorts at each follow-up interval was assessed using Pearson’s chi-square test when all expected cell counts were ≥5, and Fisher’s exact test otherwise. A two-sided P value <0.05 was considered statistically significant. All analyses were conducted separately for each surgical level and procedure type. Survival curves were plotted for visual comparison, and numerical results including HR values and corresponding P values, were tabulated.

Result

A total of 277 146 ACDF and 25 957 CDR patients meeting eligibility criteria were identified in PD. Of these, 1-level procedures accounted for 174 135 ACDF and 21 995 CDR cases, while 2-level procedures included 103 011 ACDF and 3962 CDR cases (Table 2). Additionally, 897 studies were retrieved through database searches; following removal of duplicates and screening by title, abstract, and full text, 44 studies were included. Two additional supplement studies on Simplify device^23,24 from Google Scholar, not identified by the original database search, were also screened for data collection and analysis because of their approval from the FDA trial for commercial distribution (Tables 3 and 4).

Table 2.

Demographics of PearlDiver Patients Cohort.

Characteristic	1-Level ACDF	2-Level ACDF	1-Level CDR	2-Level CDR
Number of participants	174 135	103 011	21 995	3962
Mean age (years)	53.7 ± 11.8	56.5 ± 10.7	46.06 ± 9.92	49.3 ± 9.8
ECI	3.6 ± 3.1	3.8 ± 3.1	2.75 ± 2.61	3.3 ± 2.7
Female	94 518	56 292	12 318	2174
Male	79 617	46 719	9677	1788
Myelopathy	61 503	43 707	4786	903
Radiculopathy	134 852	80 687	18 540	3363
Insurance: Commercial	133 537	77 565	19 093	3377
Insurance: Medicare	24 454	16 175	1001	233
Insurance: Medicaid	10 174	5919	1121	210
Osteoporosis	16 296	11 372	916	185

Abbreviation: ECI = Elixhauser Comorbidity Index.

Table 3.

Demographics of FDA Trials Patient Cohort.

Study name	Device name	Level	F/up period	Sites	CDR sample size	ACDF sample size	Mean age (Y)
Mummaneni 2007 25	Prestige ST	1	2	32	276	265	CDR: 43.3 ACDF: 43.9
Burkus 2010 26	Prestige ST	1	5	32	276	265	CDR: 43.3 ACDF: 43.9
Burkus 2014 27	Prestige ST	1	2 & 7	31	276	265	CDR: 43.3 ACDF: 43.9
Murrey 2009 28	Prodisc C	1	2	13	103	106	CDR: 42.1 ACDF: 43.5
Delamarter 2010 29	Prodisc C	1	4	13	103	106	CDR: 42.1 ACDF: 43.5
Zigler 2013 30	Prodisc C	1	5	13	103	106	CDR: 42.1 ACDF: 43.5
Janssen 2015 31	Prodisc C	1	7	13	103	106	CDR: 42.1 ACDF: 43.5
Heller 2009 32	Bryan	1	2	30	242	221	CDR: 44.4 ACDF: 44.7
Sasso 2007 33	Bryan	1	2	3	56	59	CDR: 43 ACDF: 46
Sasso 2011 34	Bryan	1	2 & 4	30	242	221	CDR: 44.4 a ACDF: 44.7 a
Sasso 2017 35	Bryan	1	10	1	22	25	CDR: 44.4 a ACDF: 44.7 a
Lavelle 2019 36	Bryan	1	10	30	242	221	CDR: 44.4 ACDF: 44.7
Phillips 2013 37	PCM	1	2	24	218	185	CDR: 45.3 ACDF: 43.7
Phillips 2015 38	PCM	1	5 & 7	24	218	185	CDR: 45.3 a ACDF: 43.7 a
Hisey 2014 39	Mobi-C	1	2	23	164	81	CDR: 43.3 ACDF: 44
Hisey 2015 40	Mobi-C	1	4	24	164	81	CDR: 43.3 a ACDF: 44 a
Radcliff 2017 41	Mobi-C	1 & 2	7	24	1-Level: 164 2-Level: 225	1-Level: 81 2-Level: 105	1-Level CDR: 43.3 ACDF: 44 2-Level CDR: 45.3 ACDF: 46.2
Davis 2013 42	Mobi-C	2	2	24	225	105	CDR: 45.3 ACDF: 46.2
Davis 2015 43	Mobi-C	2	4	24	225	105	CDR: 45.3 ACDF: 46.2
Radcliff 2016 44	Mobi-C	2	5	24	225	105	CDR: 45.3 ACDF: 46.2
Vaccaro 2013 45	Secure-C	1	2	18	236	144	CDR: 43.4 ACDF: 44
Vacarro 2018 46	Secure-C	1	7	18	236	144	CDR: 43.4 a ACDF: 44 a
Gornet 2017 47	Prestige LP	2	2	30	209	180	CDR: 47.1 ACDF: 47.3
Gornet 2016 48	Prestige LP	1	7	20	280	265	CDR: 44.5 ACDF: 43.9
Gornet 2019 49	Prestige LP	1	2, 5, 7 & 10	20	280	265	CDR: 44.5 a ACDF: 43.9 a
Lanman 2017 50	Prestige LP	2	7	30	209	180	CDR: 47.1 ACDF: 47.3
Gornet 2019 51	Prestige LP	1 and 2	2 and 7	30	1-Level: 280 2-Level: 209	1-Level: 265 2-Level: 180	1-Level: CDR: 44.5 ACDF: 43.9 2-Level: CDR: 47.1 ACDF: 47.3
Guyer 2025 22	Simplify	1	5	10 b	150	117	CDR: 43 ACDF: 44.1
Garrido 2010 52	Bryan	1	4	1	21	26	CDR: 40 ACDF: 43.3
Riina 2008 53	Prestige ST	1	2	1	10	9	CDR: 40.8 ACDF: 38.1
Sasso 2007 54	Bryan	1	2	3	56	59	CDR: 42.5 ACDF: 46.1
Gornet 2019 55	Prestige LP	2	10	NA	209	180	CDR: 47.1 ACDF: 47.6
Loumeau 2016 56	Prodisc C	1	7	1	22	22	CDR: 42.1 a ACDF: 43.5 a
Jackson 2016 57	Mobi-C	1 and 2	5	24	1-Level: 179 2-Level: 234	1-Level: 81 2-Level: 105	1-Level: CDR: 43.3 a ACDF: 44 a 2-Level: CDR: 45.3 a ACDF: 46.2 a
Loidolt 2016 58	Bryan	1	10	30	242	221	CDR: 44.4 ACDF: 44.7
Ghobrial 2019 59	Bryan	1	10	30	242	221	CDR: 44.4 a ACDF: 44.7 a
Anderson 2008 60	Bryan	1	2	31	242	221	CDR: 44.4 a ACDF: 44.7 a
Hacker 2005 61	Bryan	1	2	1	22	24	CDR: 44.4 a ACDF: 44.7 a
Nunley 2020 62	Mobi-C	1 and 2	7	NA	1-Level: 164 2-Level: 225	1-Level: 81 2-Level: 105	1-Level: CDR: 43.3 a ACDF: 44 a 2-Level: CDR: 45.3 a ACDF: 46.2 a
Hisey 2015 63	Mobi-C	1	5	23	164	81	CDR: 43.3 a ACDF: 44 a
Delamarter 2013 64	Prodisc-C	1	5	13	103	106	CDR: 42.1 a ACDF: 43.5 a
Phillips 2021 65	M6-C	1	2	23	160	189	CDR: 43.6 ACDF: 44.7
Phillips 2024 66	M6-C	1	5	23	160	189	CDR: 43.6 ACDF: 44.7
Davis 2014 67	Mobi-C	2	3	24	234	105	CDR: 43.3 ACDF: 44
Guyer 2021 68	Simplify	1	2	16	150	117	CDR: 43 ACDF: 44.1
Coric 2022 23	Simplify	2	2	18	182	170	CDR: 49.3 ACDF: 47.5

^aFrom prior study.

^bbased on listed Principal Investigators in Acknowledgments.

Table 4.

Index And Adjacent Segment Surgery Event in FDA Trials Patient Cohort.

Study name a	F/up period	Level	Index segment surgeries (n (%))		Adjacent segment surgeries (n (%))		Both levels b (n (%))
			CDR	ACDF	CDR	ACDF	CDR	ACDF
Mummaneni 2007	2	1	5	22	3	9	-	-
Burkus 2010	5	1	11	29	8	13	4	6
Burkus 2014	7	1	11	29	11	24	3	14
	2	1	9	19	-	-	-	-
Murrey 2009	2	1	2	9	0	1	-	-
Delamarter 2010	4	1	3	12	-	6	-	6
Zigler 2013	5	1	3	8	-	6	-	2
Janssen 2015	7	1	6	16	6	13	-	-
Heller 2009	2	1	6	8	-	-	-	-
Sasso 2007	2	1	0	2	2	2	-	-
Sasso 2011	2	1	6	8 c	6 c	5	-	-
	4	1	9	10 c	10 c	9	-	-
Sasso 2017	10	1	0	0	1	6	-	-
Lavelle 2019	10	1	5	6	12	16	-	-
Phillips 2013	2	1	10	10	2	0	1	0
Phillips 2015	5	1	17	5	0	17	-	-
	7	1	18	5	1	19	1	0
Hisey 2014	2	1	2	5	d	e	-	-
Hisey 2015	4	1	5	8	2	3	1	2
Radcliff 2017	7	1	5	10 f	6	11	-	-
	7	2	10	17 g	10	12	-	-
Davis 2013	2	2	7	12	2	- h	-	-
Davis 2015	4	2	9	16	-	-	-	-
Radcliff 2016	5	2	9	17	-	-	-	-
Vaccaro 2013	2	1	6	14	4	2	-	-
Vacarro 2018	7	1	10	22	10	23	0	16
Gornet 2017	2	2	5	15	5	6	-	-
Gornet 2016	7	1	18	29	27	22	-	-
Gornet 2019	2	1	14	19	6	10	-	-
	5	1	17	27	23	20	-	-
	7	1	18	29	27	22	-	-
	10	1	27	-	34	-	-	-
Lanman 2017	7	2	8	22	12	17	-	-
Gornet 2019	2	1	14	19	6	10	-	-
	2	2	5	15	5	6	-	-
	7	1	18	29	27	22	-	-
	7	2	8	22	12	17	-	-
Guyer 2025	5	1	6	11	3 i	7 j	3	7
Garrido 2010	4	1	0	2	1	4	0	1
Riina 2008	2	1	-	-	-	1	-	-
Sasso 2007	2	1	0	2	3	2	-	-
Gornet 2019	10	2	9	27	16	24	-	-
Loumeau 2016	7	1	0	2	0	4	-	-
Jackson 2016	5	1	4	5	2	4	2	5
	5	2	9	10	6	3	2	9
Loidolt 2016	10	1	14	20	22	32	-	-
Ghobrial 2019	10	1	-	-	22	32	-	-
	7	1	-	-	-	-	-	-
Anderson 2008	2	1	7	10	7	9	1	2
Hacker 2005	2	1	-	-	1	-	-	-
Nunley 2020	7	1	-	-	7	12	-	-
	7	1	-	-	10	12	-	-
Hisey 2015	5	1	5	8	3	6	-	-
Delamarter 2013	5	1	3	8	2	9	2	4
Phillips 2021	2	1	3	8	0	1	-	-
Phillips 2024	5	1	3	3	2	7	-	-
Davis 2014	3	2	7	14	-	-	-	-
Guyer 2021	2	1	1	4	0	2	2	-
Coric 2022	2	2	2	4	13	2 k	2	-

^aSome patients had more than 1 subsequent surgery.

^bRepresent subsequent surgery involving both index and adjacent segments.

^cSome secondary procedures were involved with both index and adjacent levels, and they were counted for index level only in this study.

^dNo reported cases of adjacent segment procedure.

^eHigher rates of adjacent segment degeneration, but no specific numbers were provided for actual adjacent segment surgeries.

^fThe adjusted number of secondary index segment procedure is 6.2%.

^gThe adjusted number of secondary index segment procedure is 10.5%.

^hACDF patients likely had adjacent-level involvement in some removals (eg, fusion extensions), but exact numbers are not provided in trial.

ⁱCase 1: Index C6/7 + adjacent C6 -T2 was excluded from the count because of thoracic level involvement.

^jCase 9: Adjacent level involving C7/T1 (original index level: C6/7) was excluded from the count because of thoracic level involvement.

^kOne adjacent segment intervention was excluded because it was at T1.

Abbreviation: F/up = Follow-up.

A comparison of survival probabilities between FDA IDE trial cohorts and PD cohorts at 2-, 4-, 5-, 7-, and 10-year follow-up intervals is presented in Table 5. For 1-level ACDF, PD cohorts demonstrated significantly higher survival probabilities at 2 years (HR = 0.48, P < 0.001), 5 years (HR = 0.78, P = 0.038), 7 years (HR = 0.38, P < 0.001), and 10 years (HR = 0.37, P < 0.001). No significant difference was observed at 4 years (HR = 0.70, P = 0.220). For 1-level CDR, PD cohorts also showed a modest survival advantage at 2 years (HR = 0.73, P = 0.002), 7 years (HR = 0.56, P < 0.001), and 10 years (HR = 0.64, P = 0.050), whereas no significant difference was detected at 4 years (HR = 1.07, P = 0.494) or 5 years (HR = 0.88, P = 0.112). In the 2-level ACDF cohort, survival probabilities were similar at 2 years (HR = 0.98, P = 0.645), but PD cohorts demonstrated significantly higher survival at 5 years (HR = 0.31, P < 0.001) and 7 years (HR = 0.36, P < 0.001). For 2-level CDR, survival rates remained high and comparable between the 2 cohorts, with no statistically significant differences at 2 years (HR = 0.94, P = 0.787), 5 years (HR = 0.69, P = 0.093), or 7 years (HR = 0.67, P = 0.211). Data for the PD cohort was not available at the 10-year follow-up for both 2-level ACDF and CDR due to the small sample size.

Table 5.

Survival Probability And Hazard Ratio.

F/up period	Cohort*	FDA (survival probability)	PD (survival probability)	HR	P-value
2-year	1-Level CDR	0.958	0.969	0.8	0.002
	2-Level CDR	0.964	0.966	0.9	0.8
	1-Level ACDF	0.921	0.961	0.5	<0.001
	2-Level ACDF	0.955	0.956	0.97	0.6
4-year	1-Level CDR	0.957	0.954	1.1	0.5
	1-Level ACDF	0.921	0.944	0.7	0.2
5-year	1-Level CDR	0.942	0.949	0.9	0.1
	2-Level CDR	0.928	0.950	0.7	0.09
	1-Level ACDF	0.921	0.938	0.8	0.04
	2-Level ACDF	0.790	0.930	0.3	<0.001
7-year	1-Level CDR	0.893	0.939	0.55	<0.001
	2-Level CDR	0.919	0.945	0.7	0.2
	1-Level ACDF	0.820	0.928	0.4	<0.001
	2-Level ACDF	0.790	0.919	0.35	<0.001
10-year	1-Level CDR	0.893	0.930	0.6	0.05
	1-Level ACDF	0.791	0.916	0.4	<0.001
	2-Level ACDF	0.729	-	-	-

*Some patients had more than 1 surgical procedure. Abbreviations: F/up = Follow-up period; FDA = Food and Drug Administration; PD = PearlDiver; HR = Hazar ratio.

Survival Analysis

Level 1 ACDF

In the Level 1 ACDF cohort, the PD group consistently demonstrated higher survival probabilities compared to the FDA IDE cohort across most follow-up intervals. At year 2, survival was 96% in the PD group vs 92% in the FDA group (P < 0.001). This difference persisted at year 5 (PD: 94% vs FDA: 92%, P = 0.038) and became more pronounced at years 7 and 10, where PD maintained survival above 92%, while the FDA group declined to 82% at year 10 (P < 0.001). The separation between curves widened substantially after year 7, highlighting a sustained survival advantage for the PD cohort at longer follow-up durations. (Figure 2).

Figure 2.

Kaplan–Meier Survival Curve (ACDF, Level 1)

Level 2 ACDF

In the Level 2 ACDF cohort, the PD group showed consistently higher survival probabilities than the FDA IDE cohort at mid- and long-term follow-up. At year 2, both groups had nearly identical survival (PD: 95.6% vs FDA: 95.5%, P = 0.645). However, by year 5, the difference became striking, with PD maintaining a survival probability of 93% compared to only 79% in the FDA cohort (P < 0.001). This trend continued at year 7, where survival remained higher in the PD group (92% vs 79% in FDA, P < 0.001). (Figure 3).

Figure 3.

Kaplan–Meier Survival Curve (ACDF, Level 2)

Level 1 CDR

In the Level 1 CDR cohort, both the FDA IDE and PD groups demonstrated high survival probabilities throughout follow-up, but the PD group consistently maintained a modest survival advantage. At year 2, survival was 97% in the PD cohort compared to 96% in the FDA group (P = 0.002). Differences narrowed at years 4 and 5, where survival remained above 94% in both groups and no statistically significant differences were observed. However, by year 7, the PD cohort again demonstrated significantly higher survival (94% vs 89% in FDA, P < 0.001). At year 10, survival declined further in the FDA group (89%) compared with 93% in the PD cohort (P = 0.050). (Figure 4).

Figure 4.

Kaplan–Meier Survival Curve (CDR, Level 1)

Level 2 CDR

In the Level 2 CDR cohort, survival probabilities remained high in both FDA IDE and PD groups throughout the follow-up period, with no statistically significant differences at any time point. At year 2, both groups demonstrated nearly identical survival (97%). By year 5, PD maintained survival at 95% compared to 93% in the FDA group (P = 0.093), and this modest difference persisted at year 7 (95% vs 92%, P = 0.211). At year 10, survival further declined in the FDA group (88%), while PD remained at 95%, though statistical testing was not available due to missing PD data. (Figure 5).

Figure 5.

Kaplan–Meier Survival Curve (CDR, Level 2)

Discussion

Our study aimed to compare the long-term outcomes of CDR and ACDF using real-world data from the PD database and FDA IDE trials. The results highlight notable differences in the risk of subsequent surgeries between these 2 datasets for both procedures. In our analysis of the CDR group, real-world data from PD showed that the risks of subsequent surgeries were generally similar to those observed in controlled trials, but with some variations across different follow-up periods. For instance, at the 7-year follow-up, the subsequent surgery rate for CDR was 6.13% in PD data compared to 10.72% in FDA trials. However, only 1-level intervention at 2-, 7-, and 10-year timepoints was able to reach statistical significance on survival analysis and observed findings for 2-level intervention could be by chance. This suggests that while CDR performs similarly in real-world settings as in controlled trials, there may be minor differences in outcomes due to variations in patient populations or clinical practices. In contrast, the ACDF group demonstrated a significant discrepancy between real-world and controlled trial settings. The risks of subsequent surgeries were substantially lower in PD data compared to FDA trials across all follow-up periods on survival analysis. For example, at the 7-year follow-up, the subsequent surgery rate for ACDF was 7.24% in PD data vs 18.04% in FDA trials (HR: 0.4, P < 0.001). This indicates that ACDF outcomes in real-world settings may be more favorable than those reported in controlled trials, possibly due to better patient selection or improved surgical techniques not captured in older IDE trials. Additionally, postoperative fusion assessment in the FDA trials was performed by radiologists and included patient-reported outcome measures, reflecting greater scrutiny than typical clinical practice and likely contributing to the observed disparity in findings.

A systematic review by Toci et al underscored the advantages of CDR in reducing ASD and enhancing clinical outcomes, findings further supported by large-scale epidemiological evidence from Singh et al.^8,69 In their cohort analysis of 433 660 patients, CDR was associated with significantly reduced rates of anterior revision (3.35% vs 4.96%, P < .001) and posterior fusion (0.79% vs 2.14%, P < .001) relative to ACDF. However, our study uniquely extends these insights by demonstrating that such benefits are also evident in real-world settings, albeit with more modest effect sizes when compared to those observed in controlled trials. This discrepancy may stem from differences in patient demographics, surgical indications, or institutional practices inherent to real-world data as opposed to the tightly controlled environments of IDE trials. Notably, it is plausible that patients presenting with more complex pathology were preferentially selected for ACDF, potentially introducing baseline disparities that attenuate the observable benefit of CDR over ACDF in controlled trials.

Tuchman et al, in a retrospective comparison of single-level CDR and ACDF, reported no significant difference in reoperation rates. ⁷⁰ Similarly, Kelly et al. noted that while CDR reduced immediate postoperative readmissions and the need for early revision surgeries, it did not offer significant advantages over ACDF in terms of long-term complication rates. ⁷¹ However, their study was limited by its reliance on a state-specific nonfederal database that excluded revisions occurring in federal institutions, potentially underestimating the true complication burden.

Further reinforcing this point, Paek et al, in a 10-year retrospective analysis using the Statewide Planning and Research Cooperative System (SPARCS) database, evaluated outcomes for patients undergoing single-level CDR (n = 835) and ACDF (n = 6615). ⁷² They found no significant difference in revision surgery risk between the 2 cohorts. Nevertheless, SPARCS is limited to data from New York State and may not capture patients who underwent revisions outside the state, thereby restricting the generalizability of the findings.

Importantly, our study addresses several of these limitations through the use of a nationally representative dataset with a broader capture of subsequent procedures, enhancing the external validity of our conclusions. By leveraging real-world evidence on a large scale, we provide a comprehensive and clinically relevant assessment of CDR and ACDF outcomes that complements and contextualizes existing trial data. Our study contributes to the existing literature by demonstrating that while the effectiveness of CDR observed in controlled trials is largely supported in real-world settings, ACDF outcomes appear even more favourable in practice than previously reported in trials. The FDA’s post-approval studies (PAS) program highlights the need for continued long-term follow-up to ensure the safety and efficacy of these devices. ⁷³ This validation is essential for guiding clinical decision-making, ensuring the long-term safety and efficacy of both procedures and helping clinicians select the most appropriate treatment based on individual patient needs and anatomical considerations.

Strength and Limitations

Although this study provides meaningful findings, several limitations should be acknowledged. First, the use of insurance claims data may introduce bias due to potential inaccuracies in coding and inconsistencies in patient follow-up. Additionally, the database only offers aggregate-level information, which limits the ability to assess detailed clinical factors such as spinal alignment before and after surgery. Furthermore, the constraints of CPT coding and the structure of the database restrict the ability to fully understand the indications for surgery, making it challenging to identify whether follow-up procedures were related to adjacent or index-level issues. Another important limitation is the inability to differentiate between devices on PD, as the database lacks specific CPT or ICD-9/10 codes for individual devices, which may obscure device-specific outcomes and trends. Finally, while this study compares FDA IDE trial results with real-world outcomes, we did not adjust for baseline population differences between the more narrowly selected trial participants and the broader, more heterogeneous real-world cohort. Nevertheless, the study highlights the value of real-world evidence in assessing surgical outcomes. Importantly, the use of the large PD dataset enhances the statistical strength of the analysis, allowing for meaningful comparisons between CDR and ACDF. By examining real-world data alongside results from IDE trials, this research offers a broader perspective on the performance of these procedures in both clinical and everyday practice settings.

Conclusion

In conclusion, our study highlights that while CDR performs similarly in real-world settings as in controlled trials for 1-level intervention, ACDF outcomes are more favourable in real-world settings compared to controlled trials. The subsequent surgery risks for ACDF were significantly lower in real-world data compared to FDA trials, suggesting improved outcomes in diverse patient populations. This validation is essential for guiding clinical decisions and ensuring the long-term safety and efficacy of these surgical procedures. Our findings support the continued use of CDR as a viable alternative to ACDF for select patients, however, further research exploring the difference in rate of index and adjacent segment surgeries in the real world is needed to understand the factors contributing to these differences and to optimize patient selection for each procedure. Ultimately, this study underscores the importance of real-world data in complementing controlled trials to provide a comprehensive understanding of surgical outcomes.

Appendix.

Mnemonic

ACDF

Anterior cervical discectomy and fusion

CDR

Cervical disc replacement

IDE

Investigational device exemption

PAS

post-approval studies

ICD

International Classification of Disease

CPT

Current Procedural Terminology

ASD

Adjacent segment disease

PD

PearlDiver

SPARCS

Statewide Planning and Research Cooperative System

ORCID iDs

Ali Issani https://orcid.org/0000-0003-0674-2294

William J. Karakash https://orcid.org/0009-0007-0777-2539

David Riopelle https://orcid.org/0000-0002-2021-7755

Raymond J. Hah https://orcid.org/0000-0001-7513-3519

Ram K. Alluri https://orcid.org/0000-0001-5919-707X

Data Availability Statement

Data is not publicly available but can be available upon request.*