J Korean Neurosurg Soc.  2012 Jun;51(6):343-349. 10.3340/jkns.2012.51.6.343.

NFlex Dynamic Stabilization System : Two-Year Clinical Outcomes of Multi-Center Study

• Coe JD
• Kitchel SH
• Meisel HJ
• Wingo CH
• Lee SE
• Jahng TA

• KMID: 2190488
• DOI: http://doi.org/10.3340/jkns.2012.51.6.343

Abstract

OBJECTIVE
Pedicle-based dynamic stabilization systems, in which semi-rigid rods or cords are used to restrict or control spinal segmental motion, aim to reduce or eliminate the drawbacks associated with rigid fusion. In this study, we analyzed the two-year clinical outcomes of patients treated with the NFlex (Synthes Spine, Inc.), a pedicle-based dynamic stabilization system.
METHODS
Five sites participated in a retrospective study of 72 consecutive patients who underwent NFlex stabilization. Of these 72 patients, 65 were available for 2-year follow-up. Patients were included based on the presence of degenerative disc disease (29 patients), degenerative spondylolisthesis (16 patients), lumbar stenosis (9 patients), adjacent segment degeneration (6 patients), and degenerative lumbar scoliosis (5 patients). The clinical outcome measures at each assessment were Visual Analogue Scale (VAS) to measure back pain, and Oswestry Disability Index (ODI) to measure functional status. Radiographic assessments included evidence of instrumentation failure or screw loosening.
RESULTS
Sixty-five patients (26 men and 39 women) with a mean age of 54.5 years were included. Mean follow-up was 25.6 months. The mean VAS score improved from 8.1 preoperatively to 3.8 postoperatively, representing a 53% improvement, and the ODI score from 44.5 to 21.8, representing a 51% improvement. Improvements in pain and disability scores were statistically significant. Three implant-related complications were observed.
CONCLUSION
Posterior pedicle-based dynamic stabilization using the NFlex system seems effective in improving pain and functional scores, with sustained clinical improvement after two years. With appropriate patient selection, it may be considered an effective alternative to rigid fusion.

Keyword

Lumbar spine; Posterior dynamic stabilization; Spinal fusion; Non-fusion stabilization

MeSH Terms

Back Pain
Constriction, Pathologic
Follow-Up Studies
Humans
Male
Outcome Assessment (Health Care)
Patient Selection
Retrospective Studies
Scoliosis
Spinal Fusion
Spine
Spondylolisthesis

Figure

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  Fig. 1 The NFlex controlled stabilization system on a mock-up spine (A) and the rod is able to elongate and compress to accommodate for the changes in distance between pedicles, as well as toggle accommodate angulation (B).

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  Fig. 2 In the unaltered lumbar spine, physiologic translational motion (flexion-extension) would be required to elongate and compress posterior elements. The distance between pedicles varies during the translational motion.

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  Fig. 3 Instrumented segments. 2 patients received dynamic treatment at L3-4 and L5-S1.

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  Fig. 4 Clinical outcome-VAS. ASD : adjacent segment disease, DDD : degenerative disc disease, NS : not significant, VAS : Visual Analogue Scale.

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  Fig. 5 Clinical outcome-ODI. ODI : Oswestry Disability Index.

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  Fig. 6 A hybrid fusion case of 47-year old female patient with degenerative spondylolisthesis at L4-L5 with spinal stenosis at L3-L4. Preoperative lateral X-ray (left), and sagittal T2-weighted MRI (middle), and postoperative lateral X-ray at 2 year after operation (right).

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  Fig. 7 A non-fusion case of 53-year old female patient with degenerative disc disease and spinal stenosis at L3-L4. Pre and post-operative lateral dynamic radiographs at 2 year after operation.

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  Fig. 8 In degenerative spinal diseases such as spinal stenosis or degenerative spondylolisthesis, PBDS can help weakened decompressed spines to stabilize and lead to a new degenerative process (upper thicker curve) after decompression. PBDS : pedicle based dynamic stabilization system.

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