5-year Results from a Prospective, Randomized Study of a Posterior Dynamic Stabilization System for the Lumbar Spine: DYNESYS

Peter Gerszten1, R. Davis2, W. Welch3, S. Kitchel4, J. Maxwell5, J. Sherman6, R. Garcia7, T. Dimmig8, R. Rodgers9, G. Lee10,

M. Sun11, N. Anand12, B. Remington13

1University of Pittsburgh, Pittsburgh, PA, 2Baltimore Neurosurgical Associates, Baltimore, MD, 3Univ. of Pennsylvania, Philadelphia, PA, 4Orthopaedic Spine Associates,

Eugene, OR, 5SpineCare Arizona, Phoenix, AZ, 6Twin Cities Orthopedics, Edina, MN, 7Orthopedic Care Center, Aventura, FL, 8Triangle Orthopedic Associates, Durham, NC,

9Indiana University Neurosurgery, Indianapolis, IN, 10Orthopaedic Specialty Center, Willow Grove, PA, 11SUNY Upstate Medical Center, Syracuse, NY, 12Cedar-Sinai Medical

Center, Los Angeles, CA, 13Pacific Regional Neurosurgery, Modesto, CA

Introduction

Surgical decompression with fusion is an accepted treatment for patients with symptomatic lumbar spondylolisthesis. A system designed for posterior lumbar stabilization without fusion was evaluated under a US FDA study. The results examining this dynamic system compared to rigid stabilization were evaluated.

The purpose of this study was to evaluate outcomes following dynamic stabilization (DS) vs. instrumented posterolateral fusion (PLF) for patients with symptomatic lumbar spondylolisthesis.

Methods Study Design: Prospective, randomized, multi-center trial.

Patient Sample: 253 patients (DS) and 114 patients (PLF) at 28 centers.

Outcome Measures: The Oswestry Disability Index and 100mm Visual Analog Scales for radicular and back pain were used. Quality of life was assessed with the SF-12 questionnaire. » Radiographs were independently analyzed.

Inclusion Criteria: Symptomatic lumbar stenosis, spondylolisthesis (≤Grade I), and candidates for instrumented fusion at 1-2 contiguous levels (L1-S1). Participants randomly received treatment with DS or instrumented PLF (2:1 ratio) and were evaluated at 3-weeks, 3-, 6-, 12-, and 24-months, and annually thereafter.

Cord

Components of the Dynesys System

Component Material Trade Name

Pedicle Screws Wrought Titanium (Ti-6Al-7Nb) PROTASUL®-100

CordPolyethylene-terephthalate

(PET)SULENE®-PET

Universal Spacers Polycarbonate urethane (PCU) SULENE®-PCU

Universal Spacer

Pedicle Screw & Set Screw

4

Results Data was available on 105/253 dynamic stabilization (DS) and 33/114

posterolateral fusion (PLF) patients at 5-year follow-up.

The DS cohort reported improvement of pain scores by 57mm and 23mm for leg and back pain, respectively.

In the PLF cohort, leg and back pain scores improved by 42mm and 17mm, respectively. The differences were significant between cohorts (p<0.05).

The mean ODI score was reduced from pre-op by 28.3 for the DS group and 27.2 for the PLF group.

Improved/maintained neurological status was reported in 81% of the DS group and 72% for the PLF group.

Results (continued)

The SF-12 Physical Component Score improved from 28 to 40 in the DS group and was higher than the PLF group (36 vs. 28).

In the DS group, 46 subjects (18%) required further surgery compared to 13 (11%) in the PLF cohort. This difference was not statistically significant.

Radiographic screw loosening for DS was 1.4% (16/1244) and 1.1% (6/546) for the PLF group, with screw breakage at 0.2% (3/1244) in the DS group and 0.2% (1/546) in the PLF group.

The DS cohort showed no kyphotic events and only 2 instances (0.8%) of spontaneous fusion.

VAS Leg Pain

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Clinical Success at 60 Months(% Successful subjects)

Dynesys Silhouette

Leg Pain 67/79 (84%) 18/26 (69%) P=0.09

ODI 61/79 (77%) 17/26 (65%) P=0.30

Neurological Status 60/74 (81%) 18/25 (72%) P=0.40

Major Complications 255/257 (99%) 114/114 (100%) P>0.99

Absence of Additional Surgical Procedures

201/257 (78%) 97/114 (85%) P=0.17

Rate of additional surgical procedures similar between groups

Conclusions

At 5 years, the subjects implanted with the Dynesys dynamic stabilization system continued to show a clinically significant improvement in… » leg, » back pain, and » SF-12 PCS

…compared to the fusion subjects.

Radiographic outcomes were also positive, with less than a 1.5% rate of negative events reported.

Disclosures

All authors participated in this United States Food and Drug Administration clinical trial under a consulting agreement with Zimmer.