A Current Review Of Outcome Studies On The Dynesys® System For Dynamic Stabilization Of The Lumbar Spine

The current article reviews the literature on the effectiveness of the Dynesys® system of dynamic lumbar spine stabilization from 2008-2010, updating the review conducted by the UK National Institute for Clinical Excellence in 2009. A systematic search was conducted using PubMed, MEDLINE, and The Cochrane Library for studies including pain and/or disability as outcome measures, yielding 13 studies. While the results of earlier studies question the advantage of the Dynesys® system, the most studies, with follow-ups as long as 52 months, reported significant, positive changes in pain and disability. These results are limited by the predominant use of case studies. The Dynesys® system is designed for the dynamic stabilization of the lumbar spine to improve stability of the spine while lessening pain and disability without the rigid fixation found in more traditional systems. While the Dynesys® system uses a traditional pedicle-based system of screws, what makes it different is that it maintains anatomical features of the lumbar spine and uses flexible materials between the pedicles. Designed and developed in France, the Dynesys® system was first implanted in 1994. 1 Some facilities, like the Orthopaedic Clinic of the S. Chiara Hospital in Pisa, Italy, have been using this system since 1999. 2 The Dynesys® system has been used worldwide in more than 40,000 surgeries. 3 A recent overview of this system is provided by Schwarzenbach and Berlemann. 4 A comprehensive review of the literature on the Dynesys® system was conducted by the National Institute for Clinical Excellence (NICE) of the National Health Service (NHS) in the United Kingdom. 5 They were unable to find any previously published reviews of the literature. This 2009 report by the NICE Interventional Procedures Program reviewed the literature on the effectiveness and safety of the Dynesys® interventional procedure of non-rigid stabilization techniques for the treatment of low back pain. This document reviewed outcome studies that included a total of 743 patients from 4 non-randomized comparative studies and 3 case series. The publication dates for these studies were, with one exception, from 2001 – 2007. The exception was one study published in 2009. Outcome measures for the reviewed studies included range of motion (ROM) and further disc deterioration, with follow-up data as long as 75 months. They also looked at patient reported outcomes such as pain, quality of life, disability, and satisfaction. Safety of the Dynesys® system was also reviewed. The review conducted by the NICE Interventional Procedures Program formed the basis for the NHS 2010 Interventional Procedure Consultation Document 6 recommendations which concluded that Dynesys®, as a dymanic stabilization technique for some patients with intractable lumbar pain is both safe and efficacious. This cleared the way for spinal surgeons in the UK to offer Dynesys® as one of a range of treatment options. The purpose of the current article is to provide an update on the results of studies that have been published since those reviewed in the NICE report. v The one exception is the article published in 2009 cited in the NICE report. 7 . In the current update, a systematic search was conducted using PubMed, MEDLINE, and The Cochrane Library from 2008 through 2010. While more than 40 articles meeting these criteria were found, and from researchers world wide, only those studies using living human patients (as opposed to animals or cadavers), and only those related to the lumbar spine, were reviewed. Articles were also limited to those that included measures of pain and/or disability. This procedure yielded 13 studies, all of which are summarized herein. A Current Review Of Outcome Studies On The Dynesys® System For Dynamic Stabilization Of The Lumbar Spine 2 of 5 STUDIES FROM 2008 Six relevant articles that considered pain and disability using Dynesys® were published in 2008. A summary of the findings of these five studies are as follows: Two of these early studies questioned the advantages of the Dynesys® System. viii, ix A third study, which looked only at radiological findings found that degeneration continued, which may have been due to the progressive nature of the disease. x The other three studies published in 2008 found more positive outcomes, with reports of Dynesys® as a possible alternative to traditional fusion, to “very good results,” to “excellent clinical and radiologic results.” Xi, Xii, Xiii A more detailed review of these studies follows. A prospective study of 37 patients 8 who underwent decompression and the use of the Dynesys® System were evaluated 3 and 12 months post-operatively. While leg, back, and overall pain improved, lumbar pain did not, leading the authors to question the advantages of the Dynesys® System. Another early study published in 2008 9 questioned the superiority of the Dynesys® System when compared to traditional fusion when they looked at outcomes for 40 consecutive Dynesys® patients. Measures of pain and activities of daily living improved for 73% of the patients with an average follow-up of 16 months. A 2008 prospective case study 10 of 32 patients who underwent spinal surgery (20 with Dynesys®; 12 with additional fusion at > 1 level) were examined to determine the radiologic changes in the intervertebral discs after the Dynesys® procedure. Pre-operative and 2-year postoperative MRIs were compared. Although these researchers found that disc degeneration at the bridged and adjacent segment continued, they could not rule out the possibility that natural disease progression caused the continuing degeneration. For 20 patients who underwent decompression and the Dynesys® System where Visual Analogue Scale Leg Pain (VAS) and disability ratings using the Oswestry Disability Index (ODI) were measured, a 2008 study 11 with more positive results after a 26 month follow-up found no implant failures, a preservation of motion in the stabilized segments, and clinical improvement. Unlike the previous two studies, these authors concluded that “dynamic stabilization systems with adequate decompression may be an alternative surgical option to conventional fusion.” Positive findings were also reported in a prospective study 12 published in 2008 that looked at 25 patients with degenerative lumber spondylolysis and central canal stenosis who received the Dynesys® system. These researchers defined the results as “very good” if there was a relative gain results of more than 70%. Actually 72% of the patients in this study had results in the very good category and 28% in the “good” category (reflecting a relative gain of 40-70%). There were no patients whose outcomes were less than “good.” These results were obtained with a follow-up objective testing ranging from 2-6 years, with a mean follow-up of nearly 3 years. Even more positive findings were reported in a prospective clinical study 13 published in 2008 that tested whether Dynesys® could maintain enough stability to prevent progression of spondylolisthesis in long-term follow-up. They used 26 consecutive patients whose symptoms included lumbar spinal stenosis and degenerative spondylolisthesis and who underwent decompression and stabilization with Dynesys®. Patients were evaluated clinically and radiologically with an average follow-up of 52 months. Pain and walking distance, which improved by year 2, were maintained at follow-up. Radiological findings were that spondylolisthesis did not progress and the spinal stability remained over time. In this study, 95% of the patients reported that they would have the same procedure again. The conclusion of these researchers was that the Dynesys® system produced significantly positive clinical and radiologic results.