7SProceedings of the NASS 23rd Annual Meeting / The Spine Journal 8 (2008) 1S–191S

PURPOSE: The purpose of this study was to evaluate disc changes at the

segments adjacent to and bridged by Dynesys dynamic stabilization system

when used in the management of chronic low back pain.

STUDY DESIGN/ SETTING: Prospective case series.

PATIENT SAMPLE: Thirty eight patients who underwent Dynesys pro-

cedure for chronic low back pain unresponsive to conservative measures,

between November 2002 and June 2005 and have completed 2-year follow

up MRI scans were included in this study.

OUTCOME MEASURES: MRI disc degeneration.

METHODS: Of the 38 patients, 26 patients underwent Dynesys procedure

alone and 12 underwent additional fusion at one or more levels. A total of 83

levels were operated upon. 70 levels were bridged only by Dynesys which

was always next to the adjacent segment. Fusion was performed at 13 levels.

Preoperative and 2-year postoperative lumbar MRI scans were evaluated by

two independent observers. Patients were scanned in the upright weight-

bearing posture using the Fonar positional MRI scanner (Melville, NY).

T2 weighted mid sagittal images were used and disc degeneration classified

according to the Woodend Classification of disc degeneration (the score for

a given intervertebral disc could vary between 15normal disc and 45most

severe degeneration detectable). Statistical analysis - for each patient at each

of the five lumbar levels mean pre- and postoperative scores were calculated

using observations from both observers. The mean pre- and postoperative

scores were then compared using paired t-test. Inter observer agreement

was measured using the weighted Kappa scores.

RESULTS: There was a statistically significant increase in the mean

Woodend score for inter-segmental levels bridged only by Dynesys from

2.20 preoperatively to 2.51 at 2 years postoperatively (p!0.001). For the

adjacent segments mean Woodend scores changed from 1.35 preopera-

tively to 1.51 postoperatively (p50.09) if only the proximal segments were

included. When both proximal and distal adjacent segments were included

the mean scores changed from 1.36 to 1.53 (p50.034). Progressive degen-

eration was noted in 8 out of 46 adjacent levels. There was good inter ob-

server agreement (weighted Kappa score of 0.819).

CONCLUSIONS: Disc degeneration at the bridged and adjacent segment

appears to continue despite Dynesys dynamic stabilization. It is difficult to

ascertain if this continuing degeneration is due to natural disease progres-

sion or the effect of stabilization. Changes seen in the adjacent segment

though seem to contradict the proposed theoretical advantage offered by

Dynesys. This however does not necessarily change the prognosis as the

incidence of asymptomatic disc degeneration is high.

FDA DEVICE/DRUG STATUS: Dynesys� System: Approved for this

indication.

doi:10.1016/j.spinee.2008.06.015

14. Two-Year Interim European Clinical Results of Nucleus

Replacement Using an In Situ Cured Balloon Contained Injectable

Polyurethane Device

John Sherman, MD1, Michael Ahrens, MD2, Hansen Yuan, MD3,

Peter Donkersloot4, Frederic Martens, MD5, Henry Halm6, Jean

Charles LeHuec, MD7, Anthony Tsantrizos, PhD8; 1Twin Cities

Orthopaedic, Minneapolis, MN, USA; 2Neustadt i.H., Germany; 3SUNY -

Upstate Medical University, Syracuse, NY, USA; 4Neurosurgery

Department, Virga Jesse Hospital, Hasselt, Belgium; 5OLV Ziekenhuis

Hospital, Aalst, Belgium; 6Clinic for Spine Surgery with Scoliosis Center,

Neustadt i.H., Germany; 7Hospital Tripode Pelligrin, Bordeaux, France;8Disc Dynamics, Inc., Eden Prairie, MN, USA

BACKGROUND CONTEXT: Nucleus replacement has received re-

newed interest as a treatment alternative to alleviate discogenic pain.

The DASCOR� device is a two-part polyurethane in situ cured nucleus re-

placement device designed to alleviate discogenic pain and restore/main-

tain disc height and segmental mobility in the mild to moderate stages

of degenerative disc disease (DDD). The device is made from a two-part

in situ cured polyurethane core and an expandable balloon. The liquid

polyurethane is implanted under controlled pressure in the expandable bal-

loon using a minimally invasive procedure. The device is a CE Mark ap-

proved product. A post-market European study is currently underway.

PURPOSE: Evaluate the interim clinical two-year safety and effectiveness.

STUDY DESIGN/ SETTING: Prospective, multicenter, non-randomized

1 - 2 year follow-up study evaluating the treatment of DDD.

PATIENT SAMPLE: 85 patients (45 male, 40 female) who underwent

minimally invasive, catheter based disc nuclus replacemnt.

OUTCOME MEASURES: Assesed pre- and postoperatively at 6, 12 and 24

monhts for ODI, VAS, analgesic medication use and radiographic imaging.

METHODS: Eight-five eligible patients with mild-moderate single-level

DDD, concordant provocation discography, significant back pain, six-month

failed non-operative care and no prior fusion surgery were enrolled in the

study. A standardized retroperitoneal anterolateral or lateral approach was

used for nucleus removal and device implantation. Outcome parameters such

as the Oswestry Disability Index (ODI), visual analog scale (VAS), analgesic

medication use, and plain film or MRI radiographic assessments were col-

lected preoperatively and throughout the duration of follow-ups. Clinical

success was defined as at least a 2 and 15 point decrease in VAS and ODI

scores, respectively. A repeated measures ANOVA was used to statistically

compare outcomes across follow-up timepoints.

RESULTS: Of the patients implanted (mean age: 3968yrs; 45 male, 40

female), 76, 65 and 24 patients were followed for 6, 12 and 24 months, re-

spectively with 98% of expected patient visits completed. Eight, 37 and 40

patients were implanted at the L3/4, L4/5, and L5/S1 levels, respectively.

Mean operating time and blood loss were 91.3 minutes and 40.0cc, respec-

tively. Mean pre-operative VAS (7.6) and ODI scores (58) improved signif-

icantly after 6 weeks (4.1 & 37) and throughout the 2 years (3.2 & 20).

Although most patients met the clinical success criteria, patients implanted

at the L5/S1 level, compared to those at the L4/5 or L3/4, experienced

a more significant decrease in ODI and VAS within the first year. Analge-

sic medication use decreased dramatically over time, with patients elimi-

nating the use of narcotic analgesics after six weeks and almost all

anti-inflammatory drugs after one year. Radiographic results demonstrated,

at a minimum, preservation of disc height, lordosis and range of motion,

with no significant Modic changes beyond Type I, nor any expulsion.

CONCLUSIONS: The two-year clinical experience demonstrated high

clinical-radiographic safety based on significant postoperative pain reduc-

tion, functional improvement, and low complication rate. The ability to im-

plant the device using a small annulotomy along with the large contact area

for axial load transmission provided by the device is believed to be respon-

sible for the positive results of this study.

FDA DEVICE/DRUG STATUS: DASCOR Disc Arthroplasty System: In-

vestigational/Not approved.

doi:10.1016/j.spinee.2008.06.016

Wednesday, October 15, 20082:05–3:05 PM

Concurrent Session 1: Lumbar Fusion

15. Comparison of Health-Related Quality of Life Following Fusion

for Lumbar Degenerative Spondylolisthesis with Hip and Knee Joint

Replacement Surgery and with Population Norms

William Sears, MBBS1, Peter McCombe, MBBS2, Owen Williamson,

MBBS3, Gavin White4; 1Macquarie University, Sydney, New South Wales,

Australia; 2Royal Brisbane Hospital, Brisbane, Queensland, Australia;3Monash University, Melbourne, Victoria, Australia; 4Medtronic Australia,

Sydney, New South Wales, Australia

BACKGROUND CONTEXT: The role of spinal fusion in patients suffer-

ing degenerative spine disease may be scrutinized more as costs of surgical