69SProceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S–205S

CONCLUSIONS: This suggests cervical disc arthroplasty appears to

achieve favorable outcomes at two-year postoperative for patients with

2-level cervical disc disease. Longer term-follow-up is required.

FDA DEVICE/DRUG STATUS: Prestige LP Cervical Disc Prosthesis:

Investigational/Not approved.

doi: 10.1016/j.spinee.2009.08.161

133. A Prospective, Randomized, FDA IDE Study of Lumbar TDR

with the Kineflex Artificial Disc vs. the Charite Artificial Disc:

Evaluation of Clinical Outcomes at 12 Months from a Single Site

Reginald Knight, MD1, Benjamin MacLennan, MD1, Jeffrey Roh, MD1,

Paul Schwaegler, MD2, James Robinson, MD3; 1Orthopedics Intl.,

Kirkland, WA, USA; 2Seattle, WA, USA; 3University of Washington,

Seattle, WA, USA

BACKGROUND CONTEXT: Both devices are similar in concept. The

Kineflex artificial disc differs with respect to the center of rotation, degree

of distraction required for implantation, and its all-metal design. These dif-

ferences may lead to clinical benefits and improved success rates.

PURPOSE: The study was intended to demonstrate that Kineflex Spinal

System using cobalt chromium molybdenum (CCM) endplates with

a CCM core is at least as safe and effective as the Charite artificial disc

when used to treat patients with single-level degenerative disc disease from

L4-S1 unresponsive to nonoperative treatment.

STUDY DESIGN/SETTING: A prospective, randomized, Food and Drug

Administration-regulated Investigational Device Exemption (IDE) clinical

trial.

PATIENT SAMPLE: Fifty-eight patients were randomized in a 1:1 ratio

to treatment with the Kineflex disc vs. Charite disc. The investigational

group consisted of 31 patients. The control group consisted of 27 patients.

There was no significant difference between the two groups with respect to

gender, age, height, weight, or body mass index.

OUTCOME MEASURES: Key clinical outcome measures included a Vi-

sual Analog Scale (VAS) assessing pain severity and the Oswestry Disabil-

ity Index (ODI). Clinical assessments were completed before surgery.

Subjects were then evaluated post-operatively at 2 weeks, 6 weeks, 3, 6,

12 and 24 months following surgery. Clinical outcomes were assessed us-

ing the VAS for pain, the ODI questionnaire, and neurological

examination.

METHODS: Fifty-eight patients were randomized in a 1:1 ratio to

treatment with the Kineflex disc vs. Charite disc. Pre-operative and

12-month post-operative data (available on 53/58591.4% of patients)

are presented here. Key clinical outcome measures included a Visual

Analog Scale (VAS) assessing pain severity and the Oswestry Disability

Index (ODI).

RESULTS: Patients in the 2 groups did not differ significantly on demo-

graphic variables, baseline ODI or VAS scores, or the level on which sur-

gery was performed (67% at L5-S1). Overall complication rate did not

differ significantly between groups. At 1 year postoperative, both groups

demonstrated statistically and clinically significant reductions in ODI (in-

vestigational group 50.1% and control group 56.6%) and VAS (investiga-

tional group 56.7% and control group 71.8%). There were no significant

differences between the 2 groups. FDA defined individual clinical success

for the study at 24 months. However, when the criteria are applied at 12

months the results did not differ significantly between groups as well

(57.1% investigational and 72.0% control). Both groups had high patient

satisfaction scores. No significant difference in time to return to work

was demonstrated between groups (investigational5140 days, con-

trol5113 days). Only one patient working preoperatively failed to return

to work within 12 months. In the investigational group, 6 patients eligible

but not working preoperatively returned to work.

CONCLUSIONS: This RCT did not demonstrate any differences in oper-

ative morbidity or 1-year clinical outcome between Charite and Kineflex

artificial disks for patients with complaints of mechanical low back pain

refractory to nonoperative treatment. Patients who received either kind

of disk demonstrated clinically meaningful reductions in ODI and VAS.

FDA DEVICE/DRUG STATUS: Kineflex: Investigational/Not approved;

Charite: Approved for this indication.

doi: 10.1016/j.spinee.2009.08.162

134. Biomechanical Comparison of the ProDisc-L, Charite, and

Maverick Lumbar Disc Prostheses

Denis DiAngelo, PhD1, Kevin Foley, MD1, Brian Morrow, MS1,

Peter Wong, BS1, Kelly Kiehm, MD2, Anthony Sin, MD1,

Rudolf Bertagnoli, MD3, Brian Kelly, PhD1; 1University of Tennessee,

Memphis, TN, USA; 2Ohio State University, Columbus, OH, USA; 3Spine

Center, St. Elizabeth Klinikum, Straubing, Germany

BACKGROUND CONTEXT: Interest in lumbar disc arthroplasty as an

alternative to fusion surgery continues to grow. The goal of disc arthro-

plasty is to replace the diseased disc while preserving and/or restoring mo-

tion at the operated spinal level. Different paradigms exist in the design of

total disc arthroplasty devices.

PURPOSE: The purpose of this study was to compare the in vitro biome-

chanics of a more constrained ball-and-socket design (Prodisc-L, Synthes

Spine and Maverick, Medtronic) and a less constrained mobile-bearing de-

sign (Charite, DePuy). The biomechanical performance of the disc prosthe-

ses was compared to a fused spine condition.

STUDY DESIGN/SETTING: N/A.

PATIENT SAMPLE: N/A.

OUTCOME MEASURES: Measurements included vertebral motions, to-

tal spine rotation, and applied loads. The percent contribution of rotation at

the instrumented (L5-S) level relative to total rotation (L1-S), as well as at

the remaining adjacent levels relative to total rotation, was determined

a common load limit (8 Nm) and compared using a one-way ANOVA

and SNK test (P!0.05).

METHODS: Twenty human cadaveric lumbar spines (L1-sacrum) were

tested in flexion, extension, lateral bending, and axial rotation under dis-

placement control. Five spine conditions were evaluated: harvested spine

(n520), L5-S lumbar disc replacement using Prodisc-L (n514), Maverick

(n58), Charite (n56), and L5-S pedicle screw fixation (PSF) (n520). The

first 12 spines were split into 2 groups: 6 were instrumented with the Charite

and 6 with the ProDisc-L. The next 8 spines tested were split into 2 groups of

4 and instrumented with either the Maverick or the ProDisc-L. After com-

pleting all tests on the second group of 8, the Maverick and

ProDisc-L discs were swapped between spines and retested. The Click’X

pedicle screw system (Synthes Spine) was used to simulate the fusion model

in all 20 spines tested. The spines were loaded to a target bending moment of

8 Nm. For axial rotation tests, a 100 N compressive load was applied.

RESULTS: A significant reduction in motion occurred at the operated

level of PSF condition compared to the three disc arthroplasty conditions

for all loading modes. No differences occurred between the 3 disc condi-

tions for all modes tested, except at the instrumented level of the ProDiscL

(93% of H) and Maverick (128% of H) spine conditions during flex-

ionþextension. The reduced motion at the operative level of the PSF con-

dition was transferred to the adjacent levels and caused a significant

increase in motion during flexionþextension at all adjacent levels for the

3 disc arthroplasty conditions, during rightþleft lateral bending at L1-L2

for all disc conditions and at L3-L4 for the Charite, and during rightþleft

axial rotation at L3-L4 for all three disc conditions.

CONCLUSIONS: Issues pertaining to adjacent segment disease (ASD)

with pedicle screw fixation were supported by the increase motion at mul-

tiple adjacent segments. However, disc arthroplasty eliminated any signif-

icant increase and may prevent ASD. Compared to pedicle screw fixation,

the three differently designed disc prostheses (Prodisc-L, Maverick, and

Charite) remained stable and provided improved lumbar mobility. The only

notable difference between the disc designs was the increased flex-

ionþextension motion at the operative level of the semi-constrained