A. AP radiograph of a patient after C6-7 diskectomy and arthroplasty using a cervical disk replacement. B and C. Flexion and extension lateral radiographs of the same patient showing motion at the treated level.Reproduced from Bolesta MJ and Gill K: Acute Neck Pain and Cervical Disk Herniation in Spivak JM and Connolly PJ (eds) Orthopaedic Knowledge Update Spine 3, Rosemont IL, American Academy of Orthopaedic Surgeons, 2006, p 232.

AAOS Now

Published 6/1/2010
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Michael R. Zindrick, MD; Fareeha Shuttari-Khan, MPH

New TO examines CDA vs. ACDF

Compares cervical disk arthroplasty and anterior cervical disk fusion

Since its introduction in the United States in 2003, the artificial cervical vertebral disk has presented physicians and patients with the prospect of achieving relief of radicular arm and neck pain, while at the same time maintaining spine segmental motion and thus eliminating adjacent segment degeneration.

Several different types of artificial disks are now available for use along with a growing body of data with longer follow-up. But whether cervical disk arthroplasty (CDA) is as good as or superior to anterior cervical disk fusion (ACDF) in relieving neck and arm pain when used to address similar clinical scenarios remains an unanswered question.

During its December 2009 meeting, the AAOS Board of Directors approved a new technology overview (TO) on CDA. Kristy L. Weber, MD, chair of the Council on Research, Quality Assessment and Technology, presented the document, which was developed by a physician workgroup under the direction of the Guidelines & Technology Oversight Committee.

In keeping with the definition of a TO, the document does not make recommendations for or against the use of CDA. TOs are considered educational tools that encourage readers to consider the information presented and reach their own conclusions.

A focus on four questions
The TO on CDA addresses the following four key questions, which were developed by a panel of physicians:

  • What patient characteristics predict successful outcomes in patients who undergo CDA compared to patients who undergo ACDF?
  • Do patients with a herniated cervical disk who present with arm pain with or without neck pain and are treated with CDA have equal or better clinical outcomes than patients treated with ACDF?
  • Do patients with a herniated cervical disk who present with arm pain with or without neck pain and are treated with CDA have equal or better revision and/or complication rates than those treated with ACDF?
  • For patients, which is more economical—CDA or ACDF—as defined by hospital length of stay (LOS) and length of time to return to work (RTW)?

The workgroup identified 2,054 citations that were potentially relevant, but only seven met the predetermined inclusion criteria. Six of these studies compared the outcomes of patients treated with single-level CDA to those of patients treated with single-level fusion with adjunctive augmentation. One study compared the outcomes of patients treated with multi-level CDA or multi-level ACDF.

Patient characteristics and outcomes
To address the first key question—on patient characteristics that might predict successful outcomes in patients undergoing CDA compared to patients undergoing ACDF—the workgroup considered the following predictors: previous surgeries per patient, all demographics available, age, sex, smoking status, workmen’s compensation status, narcotic use, opioid use, analgesic use, use of a transcutaneous electrical nerve stimulation (TENS) unit, and any ongoing pain management if evaluated in a study.

Only one of the seven included studies addressed this question with the appropriate statistical analysis. At 24 months, the authors of this level II study of 147 patients reported no statistically significant difference in the percentage of successful patients treated with CDA compared to successful patients treated with ACDF in regards to the continuation of the use of strong narcotics and muscle relaxants. These results were inconclusive as to what patient characteristics predict successful outcomes in CDA patients compared to ACDF patients.

A. AP radiograph of a patient after C6-7 diskectomy and arthroplasty using a cervical disk replacement. B and C. Flexion and extension lateral radiographs of the same patient showing motion at the treated level.Reproduced from Bolesta MJ and Gill K: Acute Neck Pain and Cervical Disk Herniation in Spivak JM and Connolly PJ (eds) Orthopaedic Knowledge Update Spine 3, Rosemont IL, American Academy of Orthopaedic Surgeons, 2006, p 232.

Clinical outcomes
To address the second question—which treatment produces better clinical outcomes for patients with both arm and neck pain or with only arm pain—the workgroup reviewed five level II studies.

  • Three of the studies reported that patients treated with CDA had statistically significantly lower Neck Disability Index (NDI) scores than patients treated with fusion at earlier follow-up durations (1.5–3 months). Results at longer follow-up durations are inconclusive.
  • Two of the studies reported that patients treated with CDA had statistically significantly higher NDI success rates at 3 months than patients treated with ACDF. No statistically significant differences were reported at later follow-up durations.
  • Two of the studies reported no statistically significant differences in neurologic success rates between treatment groups at all follow-up durations. One study reported that patients treated with CDA had statistically significantly higher neurologic success rates at 12 months.
  • Four of the studies reported no statistically significant differences in neck pain at earlier follow-up durations (1–6 months). One study reported patients treated with CDA had statistically significantly less neck pain than patients treated with ACDF. The results reported at later follow-up durations are inconclusive.
  • Three of the studies reported no statistically significant differences in arm pain scores at all follow-up durations. One study reported that at 24 months, patients treated with CDA at multiple levels had statistically significantly less arm pain compared to patients treated with multi-level ACDF.
  • Three of the studies reported results for the Short-Form 36 physical component, but these were contradictory and inconclusive.
  • Two studies reported no statistically significant differences in the number of patients who returned to work at 24 months and one study reported similar results for patients returning to “heavy work” at 24 months.

Revision Rates
The third question focused on whether CDA or ACDF had better revision rates for patients with arm pain only or with both arm and neck pain. The workgroup reviewed four level II studies. They found that the results of secondary surgical procedures reported by three of the studies were inconclusive because the authors of these studies did not report or measure secondary surgical procedures of patients in a similar way. Consequently, the results could not be compared. The results of any adverse events of patients reported by four of the studies considered for this question were also inconclusive.

Economic Value
To address the final question on economic value for the patients, the workgroup reviewed four level II studies. No statistically significant differences were reported in the length of hospital stay for patients treated with CDA compared to patients treated with ACDF. Patients treated with CDA returned to work in statistically significantly fewer days (range: 14–16 days) than patients treated with ACDF.

The complete TO on CDA, including detailed evidence tables, can be found on the AAOS Web site at www.aaos.org/technologyoverviews

Michael R. Zindrick, MD, chaired the physician workgroup on the technology overview on cervical disk arthroplasty. He reports no relevant conflicts of interests and has completed the AAOS online disclosure. Fareeha Shuttari-Khan, MPH, is the AAOS Evidence-Based Medicine Coordinator and reports no conflicts of interest.

Developing a technology overview
The workgroup on “Cervical Disk Arthroplasty: A technology overview” was chaired by Michael R. Zindrick, MD, and included Mitchel B. Harris, MD; Steven Craig Humphreys, MD; Patrick T. O’Leary, MD; Gary A. Schneiderman, MD; William C. Watters III, MD, chair of the Guidelines & Technology Oversight Committee; Charles Turkelson, PhD; Jan Wies, MPH; and Laura Raymond, MA.

The TO on CDA is not intended to convey any official position by the AAOS. Instead, the information is provided as a service to help members identify and evaluate the available published literature on this topic so that they can provide the best possible care to their patients.

AAOS is involved in the development of TOs because technology plays a central role in the practice of orthopaedic surgery. In addition, AAOS seeks to be a resource for those seeking unbiased information on newly developed surgical procedures, drugs, biologics, and orthopaedic devices. The TO was funded solely by the AAOS.

Additional Resources:

Levels of Evidence: A Step Forward on the Road to Better Practice? (in PDF format)
This article introduces levels of evidence. It defines the five different levels of evidence, identifies potential uses, and discusses implications and effects of using levels of evidence.