86S Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.201

165. Preliminary 3-Year Results from a Prospective, Randomized,

Controlled IDE Study of the Dynesys Dynamic Stabilization System

Reginald Davis, MD1, Rick Delamarter, MD2, James Maxwell, MD3,

William Welch, MD, FACS, FICS4, Jeffrey Wingate, MD5, John Sherman,

MD6; 1Baltimore, MD, USA; 2Santa Monica, CA, USA; 3Scottsdate, AZ,

USA; 4Philadelphia, PA, USA; 5Michigan Spine Institute, Waterford, MI,

USA; 6Twin Cities Orthopaedic, Minneapolis, MN, USA

BACKGROUND CONTEXT: Background Context: Patients with radic-

ular pathology due to spondylolisthesis or stenosing lesions are typically

treated with decompression and spinal fusion. A posterior stabilization sys-

tem has been developed to stabilize the segment without the need for fu-

sion. Preliminary long-term outcomes from a cohort of patients in an

IDE clinical trial examining dynamic stabilization with the Dynesys Dy-

namic Stabilization System are being reported.

PURPOSE: Purpose: The purpose of this study is to evaluate and compare

long-term clinical outcomes following posterior dynamic stabilization or

instrumented, posteriolateral fusion.

STUDY DESIGN/SETTING: Study Design/Setting: Long-term follow-

up of a patient cohort that participated in a prospective, randomized, con-

trolled, multi-center clinical trial.

PATIENT SAMPLE: Patient Sample: This preliminary data set includes

3-year outcomes from 89 patients following dynamic stabilization (DS) pa-

tients and 45 patients treated with posterolateral fusion (PLF). This cohort

is part of an IDE study which consisted of 253 (DS) and 114 at 28 centers.

OUTCOME MEASURES: Outcome Measures: Lower limb and back

pain were evaluated using 100 mm visual analog scales. The Oswestry Dis-

ability Index (ODI) was used to evaluate patient functioning and the Short

Form-12 questionnaire was used to assess the participants’ general health.

Overall patient satisfaction was reported as well as the likelihood to

recommend.

METHODS: Outcome Measures: Lower limb and back pain were evalu-

ated using 100 mm visual analog scales. The Oswestry Disability Index

(ODI) was used to evaluate patient functioning and the Short Form-12

questionnaire was used to assess the participants’ general health. Overall

patient satisfaction was reported as well as the likelihood to recommend.

RESULTS: Results: At 36 M, the DS cohort reported 54.7 mm improve-

ment in leg pain scores, a reduction in ODI scores of 31.7, 30.1 mm im-

provement in back pain, and 91% of subjects either improved or

maintained their level of neurological success compared to pre-op assess-

ment. In the PLF cohort, leg pain scores improved by 48.4 mm, ODI scores

were reduced by 26.9, back pain scores improved by 20.5 mm, and 93% of

subjects reported improved or maintained neurological success compared

to pre-op evaluation. VAS back pain, patient satisfaction, and likelihood

to recommend scores reported at 36-months were statistically significant

between groups (p!0.05). Additionally, 36 M data shows a 14.1 point

and 7.8 point improvement in SF-12 Physical Component and Mental

Component scores, respectively, for the DS cohort. Similar results were re-

ported in the PLF group. The revision rate for the DS group was 28% and

23% for the PLF cohort.

CONCLUSIONS: Conclusions: Preliminary long-term clinical outcomes

from an IDE clinical trial are reported. At 36 M, the subjects implanted

with the Dynesys Dynamic Stabilization System show an improvement

in ODI, Neurological Success, leg pain and SF-12 scores and a significant

improvement in back pain, VAS patient satisfaction, and VAS likelihood to

recommend scores compared to the control group.

FDA DEVICE/DRUG STATUS: Dynesys: Investigational/Not approved.

doi: 10.1016/j.spinee.2009.08.202

Friday, November 13, 20094:10–5:10 PM

Focused Paper Presentations 1:DeformitydPediatric

166. A Novel Method for Assessing the Axial Plane in Scoliosis

Demonstrates Uniplanar Screws Outperform Polyaxial Screws

Dalal Aliasgar, MD1, Peter Newton, MD2, Vidyadhar Upasani, MD3,

Suken Shah, MD4; 1San Diego, CA, USA; 2Children’s Hospital and Health

Center - San Diego, San Diego, CA, USA; 3University of California, San

Diego, San Diego, CA, USA; 4Wilmington, DE, USA

BACKGROUND CONTEXT: The effect of uniplanar versus polyaxial

screws on the axial rotation of the adolescent idiopathic scoliosis (AIS) pa-

tient is uknown.

PURPOSE: The purpose of this study was to compare the correction of

axial plane deformity in thoracic AIS achieved with uniplanar and polyax-

ial thoracic pedicle screw constructs.

STUDY DESIGN/SETTING: A review of a multi-center, prospective

database.

PATIENT SAMPLE: Lenke Type 1-3 AIS patients who underwent surgical

correction of thoracic AIS by posterior segmental pedicle screw instrumen-

tation and fusion with either uniplanar or polyaxial pedicle screws and

5.5 mm steel rod constructs was performed. Curves O100� were excluded

to control for the propensity to use polyaxial screws to correct larger curves.

OUTCOME MEASURES: Apical vertebral rotation was evaluated based

on an innovative CT scan validated radiographic method that uses the rel-

ative position of the screw tips to grade rotation.

METHODS: Apical vertebral rotation of thoracic curves was graded as 0,

1, or 2 at the 6 week and 1 year post-operative visit. By this method, higher

grades correspond to greater residual apical vertebral rotation.

RESULTS: 210 patients met inclusion. The uniplanar group included 95

patients while the polyaxial group had 115 patients. The mean pre-opera-

tive thoracic Cobb angle of 58612� and 60613� (p50.1), first erect post-

op coronal correction of 72% and 74% (p50.38) and one year correction

of 70% and 76% (p50.07) were not significantly different between the uni-

planar and polyaxial groups, respectively. At 6 weeks post-op, the unipla-

nar group had 34% of patients with grade 0, 52% with grade 1 and only

14% with grade 2 thoracic apical vertebral rotation. In the polyaxial group

only 14% of patients were grade 0, 35% were grade 1 and 51% were the

most rotated grade 2. This was a significant difference in the distribution of

axial rotations (p!0.001), with greater axial correction with uniplanar

screws. The same pattern of results was found at 1 year post-op (p!0.001).

CONCLUSIONS: There was little difference in the coronal plane correc-

tion of thoracic curves. However the uniplanar pedicle screw group had

a larger proportion of patients with greater thoracic apical vertebral dero-

tation (more complete axial correction) compared to the polyaxial screw

group. This is likely attributed to the increase in rotational leverage af-

forded by uniplanar screws during intraoperative bilateral direct apical ver-

tebral derotation maneuvers.

Figure. Breakdown of Thoracic Apical Vertebral Rotation Grades.

FDA DEVICE/DRUG STATUS: Pedicle Screw: Not approved for this

indication.

doi: 10.1016/j.spinee.2009.08.204