Dynamic Stabilization Systems: MedSun Small Sample Survey Summary
MedSun: Newsletter #54, November 2010

Survey Topic: Dynamic Stabilization Systems
Year Conducted: 2009


Background
An estimated 200,000 spinal fusion procedures are performed each year in the United States with a projected increase due to an aging population. As these procedures have become more common, FDA wanted to better understand how surgeons are using pedicle screw based posterior spinal stabilization systems that include “dynamic” or motion-preserving features. FDA has received over 100 adverse event reports involving these systems from a variety of manufacturers. Also, there was a recall in 2008 by Medtronic for the Agile model due to device cable failure. A survey was conducted to gather information from orthopedic surgeons about their use of these systems and the clinical outcomes. Five surveys from five different facilities were completed; two by phone interviews and three by written questionnaires. The questions included the types of systems used, indications for treatment and the experience and clinical outcomes with these devices.

Summary
The most commonly used dynamic stabilization systems by the respondents are the Zimmer Spine Dynesys and DTO, the Medtronic Sofamor Danek - CD Horizon PEEK Rods, and the Depuy Spine –Viper and Expedium PEEK Rods systems. Experience with these devices ranges from six months to more than four years. The most common systems are usually used in multi-level procedures, ranging from 1-4 levels. Since their initial use with these devices, most respondents have completed about ten procedures, one has performed an estimated 300.

All of the respondents stated that they treat the lumbar level of the spine. Most performed fusion procedures with half of the respondents also performing non-fusion and hybrid procedures. The most commonly treated indications are degenerative disc disease followed by spinal stenosis, spondylolisthesis, and failed spinal fusion.

Other pedicle screw based dynamic stabilization systems are used less frequently including the Medtronic Sofamor Danek Agile after the recall. The reasons for infrequent use include cost, less experience with the device, and different indications. About half said that the way in which they use the devices has changed over time, including the adoption of a more hybrid construct.

Adverse events with these systems were reported infrequently. One reason given was that it was too soon after the procedure for problems to show up. Recurrence of symptoms was noted in about 10% of one respondent’s patients but was attributed to the patients’ history. Another reported an adverse event involving junctional disc disease but said it was unrelated to the device’s failure. The respondents stated that adverse events most commonly occurred anywhere from 1-6 years after implantation.

Types of secondary surgical interventions performed included device removal and conversion to fusion with a rigid rod system, addition of supplemental fixation, additional decompression, and device revision. One respondent said during device revision, the same device was replaced and an interbody spacer was added. These secondary surgical interventions usually occurred 4-6 years after implantation.

Clinical outcomes for fusion status, pain/function scores, and neurological status ranged from good to excellent. Outcomes based on the intended uses of fusion, non-fusion, and hybrid also ranged from good to excellent. For indications of degenerative disc disease, spinal stenosis, and spondylolisthesis the ratings were good. The clinical outcome for treatment of one level of the spine was excellent while the outcome for treatment of two levels or higher was good. None of the respondents have evaluated radiographs at this point in time to obtain range of motion data.

Small scale surveys are one of many tools the Agency uses to evaluate the public health impact of the potential problems associated with the use of medical devices. Because these surveys utilize a small sample size that is not statistically derived, the results provide only qualitative and not quantitative results. Additionally, FDA continues to receive adverse event reports from its Medical Device Reporting program, and will continue to make use of the literature and other published information. FDA scientific, medical, nursing and engineering staff are made aware of the survey results as needed. If FDA believes a possible public health problem may be emerging from the results of a survey, it will combine those results with data gained from the other sources and may convene an Ad Hoc group of clinical and manufacturing representatives to discuss further actions.

FDA will work with the manufacturers and health care professional organizations to make important information known about medical devices to the clinical community.


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Small Sample Survey Questions

Please check the answers below (double-click the box if using electronically). If necessary, fill in the appropriate dialog (click on the yellow box and then start typing).

1. Please identify the one system below that you most commonly use and the approximate number of procedures you have performed since you began use.
Manufacturer – Device):
0 Zimmer Spine - Dynesys and DTO
0 Medtronic Sofamor Danek - Agile
0 Synthes - NFix II (also known as NFlex, NHance, or NGarde)
0 Scient’x - Isobar
0 Medtronic Sofamor Danek - CD Horizon PEEK Rods
0 Depuy Spine - Viper and Expedium PEEK Rods
0 Paradigm Spine - DSS
0 Biospine - BioFlex
0 Globus Medical - AccuFlex Rods
0 Vertiflex - Dynabolt
0 Other:

Approximate number of procedures performed with this device since initial use?

2. Are there other pedicle screw based “dynamic stabilization” systems you use less often?
0 Yes
0 No

If yes, please list them and explain why they are used less commonly (i.e. experienced adverse events, appeared less favorable in the literature or at a conference)?

NOTE: The remaining questions refer to the one system you use most often.

3. With the device that you use most often, do you perform (check all that apply):
0 Single level procedures
0 Multi-level procedures - up to how many levels?
0 N/A

4. What spinal levels do you treat (check all that apply)?
0 Lumbar
0 Thoracic
0 Cervical
0 N/A

5. Do you perform (check all that apply):
0 Fusion procedures
0 Non-fusion procedures
0 Hybrid procedures (fusion at one level and non-fusion at an adjacent level)
0 N/A

6. What indications are you treating most often (check all that apply)?
0 Degenerative disc disease
0 Kyphosis
0 Failed Spinal Fusion
0 Spondylolisthesis
0 Spinal Stenosis
0 N/A
0 Other (Please List):

7. How long have you been using the device?
0 Less than 6 months
0 1-2 years
0 2-3 years
0 3-4 years
0 4+ years
0 N/A

8. Has the way in which you use the device changed over time?
0 Yes
0 No
0 N/A
If yes, how and why?

9. What types of adverse events have you observed and how many of each type have you observed?

10. How long after implantation do these adverse events most commonly occur?
0 0-6 months
0 7-12 months
0 1-2 years
0 2-4 years
0 4-6 years
0 6+ years
0 N/A

11. In your opinion, what do you think contributed to these events?

12. What types of secondary surgical interventions have you performed (check all that apply)?
0 Device removal and conversion to fusion with rigid rod system
0 Addition of supplemental fixation
0 Additional decompression
0 N/A
0 Device revision (Briefly explain the revision surgery performed and any replacement devices that were implanted)
0 Other:

13. How long after implantation do these secondary surgical interventions most commonly occur?
0 0-6 months
0 7-12 months
0 1-2 years
0 2-4 years
0 4-6 years
0 6+ years
0 N/A

For questions 14-17 below, 5=Excellent, 4=Good, 3=Fair, 2=Poor, 1=Very Poor.

14. How would you rate the clinical outcomes in reference to the following:

Pain/Function Scores:
1.0 2.0 3.0 4.0 5.0 N/A

Fusion Status (If fusion was intended):
1.0 2.0 3.0 4.0 5.0 N/A

Neurological Status:
1.0 2.0 3.0 4.0 5.0 N/A

15. How would you rate the outcomes based on the following intended uses:

Fusion:
1.0 2.0 3.0 4.0 5.0 N/A

Non-Fusion:
1.0 2.0 3.0 4.0 5.0 N/A

Hybrid:
1.0 2.0 3.0 4.0 5.0 N/A

16. How would you rate the outcomes based on the indications being treated:

Degenerative Disc Disease:
1.0 2.0 3.0 4.0 5.0 N/A

Kyphosis
1.0 2.0 3.0 4.0 5.0 N/A

Failed Spinal Fusion
1.0 2.0 3.0 4.0 5.0 N/A

Spondylolisthesis:
1.0 2.0 3.0 4.0 5.0 N/A

Spinal Stenosis:
1.0 2.0 3.0 4.0 5.0 N/A

17. How would you rate the outcomes based on the number of levels treated:

1 level:
1.0 2.0 3.0 4.0 5.0 N/A

2 levels:
1.0 2.0 3.0 4.0 5.0 N/A

3+ levels:
1.0 2.0 3.0 4.0 5.0 N/A

18. Have you evaluated any radiographs to look at range of motion data? If yes, would you be willing to provide any available de-identified data?
0 Yes
0 No



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