Elsevier

The Spine Journal

Volume 13, Issue 1, January 2013, Pages 5-12
The Spine Journal

2012 Outstanding Paper: Surgical Science
Symptomatic adjacent segment disease after cervical total disc replacement: re-examining the clinical and radiological evidence with established criteria

https://doi.org/10.1016/j.spinee.2012.11.032Get rights and content

Abstract

Background context

Although several publications in the last decade have proved equality in safety and efficacy of the total disc replacement (TDR) to the anterior fusion procedure in cervical spine, the claim that TDR may reduce the incidence of adjacent segment disease (ASD) has not been corroborated by clinical evidence.

Purpose

We attempt to predict the true incidence of symptomatic ASD after TDR surgery in the cervical spine at one or two levels at a median follow-up period of 4 years.

Study design

A total of 763 patients were screened to participate in four different Food and Drug Administration device exemption trials for artificial cervical disc replacement at three collaborating institutions. Two hundred seventy-one patients qualified and enrolled in the trials. One hundred seventy-three randomized to receive artificial disc replacement surgery, and 167 have completed a 4-year or longer follow-up.

Outcome measures

Patients experiencing cervical radiculopathy symptoms in the follow-up period were worked-up with clinical examinations, magnetic resonance imaging of the cervical spine, and other diagnostic studies. Once a clinical correlation was established with the imaging evidence of adjacent segment degeneration, a careful record was maintained to document the subsequent medical and/or surgical treatment received by these patients. Statistical analysis was performed to determine the true incidence of and factors affecting the ASD after cervical disc replacement in these patients.

Results

Twenty-six patients (15.2%) were identified to satisfy our criteria for ASD at the median follow-up of 51 months, with the annual incidence of 3.1% as calculated by life tables. The actuarial 5-year freedom from ASD rate was 71.6%±0.6%, and the mean period for freedom from ASD was 70.4±2.1 months.

Conclusions

The incidence of symptomatic ASD after cervical TDR is 3.1% annually regardless of the patient's age, sex, smoking habits, and design of the TDR device. The presence of osteopenia and lumbar degenerative disease significantly increase the risk of developing ASD after anterior cervical surgery.

Introduction

Evidence & Methods

Adjacent segment degeneration (ASD) can occur following both anterior cervical discectomy and fusion (ACDF) and cervical disc replacement. The authors present their experience with the latter.

Using prospective data collected from four different randomized trials, the authors found that at 4 years, 15% of patients had symptomatic ASD with a 3% annual incidence following disc replacement. Osteopenia and lumbar disc degeneration were identified as risk factors. While comparison with the ACDF groups from these trials was not a primary goal of the study, it is of note that symptomatic ASD was not significantly higher in patients following ACDF (and, indeed, trended lower).

These data are valuable for informed consent. Similarly selected patients may anticipate an approximately 15% likelihood of clinically important adjacent level problems, in addition to known success/failure rates at the surgical level, by 4 years after surgery.

—The Editors

Anterior cervical fusion surgery has been implicated with an increased incidence of degenerative changes observed in the neighboring segments. These changes have been well recognized as an unintended consequence of the cervical spine surgery [1]. The magnetic resonance imaging (MRI) evidence of these changes was described by Baba et al. [2] and later corroborated by Bohlman et al. [3] and Cherubino et al. [4] independently. However, the clinical implications of such observed changes continue to remain debatable [5], [6]. Hilibrand et al. [7] finally addressed this issue and, in a pivotal article, predicted the incidence of symptomatic adjacent segment disease (ASD) after cervical fusion procedure. Their work was focused on only those patients who developed radicular or myelopathic symptoms after the anterior cervical discectomy and fusion (ACDF) surgery and demonstrated radiographic evidence of degeneration on MRI or computed tomographic scans of the cervical spine. Wigfield et al. [8], in their biomechanical study, subsequently suggested that adjacent segment degeneration could be a consequence of added stress on these segments because of restricted motion at the fused levels and that cervical total disc replacement (TDR) allows reduced stress at the adjacent levels.

In the last decade, several published studies [1], [9], [10], [11] have attempted to provide clinical proof that cervical TDR would result in a reduced incidence of adjacent segment degeneration (symptomatic or otherwise) in the cervical spine. Although all these studies quote the work of Hilibrand as a benchmark for the incidence of ASD after ACDF, none of them use the same parameters for assessing the incidence of ASD in their patients of TDR surgery. Jawahar et al. [12] attempted to compare the incidence of ASD in their patients from a single institution according to the Hilibrand criteria but could not establish the advantage of TDR in reducing the incidence of ASD at a median of 28 months after the index surgery. However, a relatively short follow-up period and a small cohort of patients were the principle weakness of that study.

In this article, we attempt to predict the true incidence of symptomatic ASD after TDR surgery in cervical spine at one or two levels at a median follow-up period of 4 years.

Section snippets

Study design

Since 2005, three collaborating institutions have participated as investigational sites to assess the clinical safety and efficacy of four different artificial cervical discs. A total of nine qualified surgeons were involved as clinical investigators in the four prospective randomized trials. Trials were conducted under the oversight of the Institutional Review Board with strict adherence to the guidelines of Good Clinical Practices. All four disc replacement devices had satisfied the Food and

Demographic considerations

One hundred sixty-seven patients completed their last follow-up visit (median follow-up, 56 months; range, 51–82 months). Patients who did not complete at least 4 years follow-up have not been included in the analysis. The mean patient age was 47 years (range, 26–66 years). There was a slight female predominance (56.6%). The protocols required us to categorize the patients into smokers (currently smoking one or more packs per day) and nonsmokers. Seventy-one patients (42.5%) admitted to being

Discussion

Adjacent segment degeneration is an established phenomenon after anterior cervical spine fusion surgery [1]. Hilibrand and Robbins [13], in a published review after their initial clinical publication, acknowledged the lack of direct correlation between ASD and cervical spine instrumentation. They attempted to differentiate between adjacent segment degeneration and ASD in their review and to consider the role that spinal fusion might play in the development of the two entities. Analyzing the

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FDA device/drug status: Approved (Bryan cervical disc, Prodisc-C); Investigational (Kineflex-C, Mobi-C).

Author disclosures: PDN: Royalties: Biomet Spine (B), Osprey Biomedical (B), LDR Spine (B); Stock Ownership: Amedica (D), Paradigm Spine (C), Spineology (E); Speaking/Teaching Arrangements: K2M (C); Scientific Advisory Board/Other Office: K2M (C); Grants: Cervical Spine Research Society (E, paid directly to institution). AJ: Consulting: K2M (B), Sea Spine (B), Allosource (B, paid directly to institution), K2M (B, paid directly to institution); Speaking/Teaching Arrangements: Nucel (B); Grants: Cervical Spine Research Society (E, paid directly to institution). DAC: Nothing to disclose. CRG: Royalties: Osteomed (F), LDR Medical (E), Exatech Spine (A); Stock Ownership: Flexuspine (F, 8% ownership); Trips/Travel: Flexuspine (stock ownership disclosed, paid directly to institution). EJK: Speaking/Teaching Arrangements: Allosource, Inc. (B); Trips/Travel: Allosource (B, paid directly to institution). PAU: Nothing to disclose.

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