132S Proceedings of the NASS 25th Annual Meeting / The Spine Journal 10 (2010) 1S–149S

RESULTS: Two (6.5%) in 31 patients were diagnosed as RLS after sur-

gery. The average onset of symptoms was third days after surgery. The

symptoms were relieved by oral iron supplements and dopaminergic ago-

nists and spontaneously disappeared within postoperative 3 months. In all

patients, Hb and serum iron showed immediately significant drops after

surgery and slowly recovered during postoperative 3 months. The patients

with RLS showed lower preoperative Hb (13.0 vs. 14.1), serum ferritin (48

vs. 120 ng/mL) and more decrease of serum iron at postoperative 2nd and

5th day (83% vs. 70%, 74% vs. 65%) than those of patients without RLS

(Figure 1). Age, sex, number of fusion levels, amount of EBL and postop-

erative drainage, use and amount of transfusion did not have statistically

significant effect on developing RLS after surgery.

CONCLUSIONS: Acute decrease of serum iron by the perioperative

bleeding can cause a secondary RLS and transient leg pain after posterior

decompression and fusion. The symptoms are developed within postoper-

ative 1 week and spontaneously resolved according to recovery of serum

iron. Lower preoperative serum ferritin might be risk factors of postoper-

ative RLS.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2010.07.340

P65. The Effects of Age, Sex, Race, and Weight on the Rate

of Intervertebral Disc Degeneration

Krzysztof Siemionow, MD1, Howard An, MD1, Koichi Masuda, MD2,

Gunnar Andersson, MD1, Gabriella Cs-Szabo, PhD1; 1Rush University

Medical Center, Chicago, IL, USA; 2University of California, San Diego,

San Diego, CA, USA

BACKGROUND CONTEXT: Intervertebral disc (IVD) degeneration is

believed to begin as early as the second decade of life, and is viewed by

most as an inevitable consequence of ageing. Age, sex, race, weight and

lumbar level are some of the factors that play a role in IVD degeneration.

The rate at which IVDs degenerate has not been established.

PURPOSE: The purpose of this study was to find the rate of IVD degen-

eration with ageing and to establish if there is a difference between lumbar

levels. Knowing the annual rate of IVD degeneration could result in im-

proved clinical decision making.

STUDY DESIGN/SETTING: A magnetic resonance imaging (MRI)

study of fresh cadaver lumbar spines.

METHODS: Complete lumbar spine segments (T11/12 to S1) which were

harvested from fresh cadavers underwent MRI. The nucleus pulposus,

annulus fibrosus, cartilaginous and bony end-plate, and the peripheral ver-

tebral body were assessed with MRI and IVD degeneration was graded by

two observers from grade 1 (nondegenerated)-grade 5 (severely degener-

ated) based on a scale developed by Thompson et al. Age, sex, race, weight

were recorded and used for statistical analysis. Statistical analysis was per-

formed using simple and multiple linear regression as well as simple mean

comparisons using analysis of variance and t-tests.

RESULTS: 435 cadaver spines and 1684 IVDs were available for analysis.

There were 302 male and 133 females. The age range was 14–81, average

age was 60.5. Regression analysis revealed that age predicted deterioration

at all lumbar levels and that the L5/S1 IVD degenerated at a significantly

faster rate of 0.040/year compared to 0.031, 0.032, 0.031, 0.028 for L12,

L23, L34, L45, respectively. Multiple regression analysis revealed that

sex and weight had no significant effect on IVD degeneration whereas

non-Caucasian race was associated with lower Thompson score at L12,

L23, L34.

CONCLUSIONS: The relatively early degeneration at L5-S1 in all races

and less degeneration in the upper lumbarmotion segments in non-Caucasian

race needs further investigation.Other factors such as sagittal alignment, fac-

et joint arthritis, and genetic predisposition may also play a role in IVD

degeneration.

All referenced figures and tables will be available at the Annual Mee

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2010.07.341

P66. Biomechanics of Disc Arthroplasty: What Can Be Done to

Improve Results: Present and Future Perspectives

Leonardo Oliveira, BSc1, Luis Marchi, MD2, Etevaldo Coutinho, MD2,

Luiz Pimenta, MD, PhD2; 1Universidade Federal de Sao Paulo, Sao Paulo,

Brazil; 2Instituto de Patologia da Coluna, Sao Paulo, Brazil

BACKGROUND CONTEXT: Current lumbar total disc replacement

(TDR) devices require an anterior approach for implantation.The anterior ap-

proach to place lumbar TDR devices has inherent biomechanical limitations

and surgical risks. Within the possible intraoperative issues are: the damage

to various abdominal structures, such to the grand vessels, to bowel compo-

nents and to the sympathetic neural plexus, without mentioning the long dis-

charge and rehabilitation time. Besides the surgical risks, there is resection of

the anterior longitudinal ligament (ALL). Placement of a TDR device from

a true lateral (XLIF) approach allows for easier, less invasive access to the

disc space, as has been shown in reports of XLIF for fusion procedures. Lat-

eral implantation of TDR also preserves the stabilizing ligaments, which are

a natural restraint to excessive rotations and translations, and thereby help to

minimize facet stresses. Importantly, implantation from a lateral approach

leaves greater opportunity for safer revision surgery, if necessary, by avoiding

scarring of anterior vasculature.Additionally, the footprint of the lateral TDR

device capitalizes on the biomechanical support of the ring apophysis.

PURPOSE: To present the clinical and radiological results of a true lateral

implantation of total disc replacement.

STUDY DESIGN/SETTING: Prospective, non randomized clinical trial

to evaluate the safety and effective of the lateral total disc replacement im-

planted by the XLIF approach.

PATIENT SAMPLE: Patients included 16 males and 20 females, average

age 43 yrs (24–60).

OUTCOMEMEASURES: VAS pain scores improved from an average of

9.3 at pre-op to 2.27 after 3 years. Oswestry Disability Index improved

from an average of 57 at pre-op to 16.5 after 3 years.

METHODS: A TDR device designed for implantation through a true

lateral, retroperitoneal, transpsoas approach (XLIF) was implanted in 36

patients with discography-confirmed 1- or 2-level DDD. Clinical and

radiographic outcomes assessments were prospectively collected.

RESULTS: Surgeries included 14 1-level, 3 2-level, and 19 hybrid TDR/

ALIF cases. The surgery was performed through a 4 cm lateral incision in

an average of 134 minutes (90–300) and with an average 58 cc blood loss

(30–150). There was no intra-op or post-op complications. Postoperative

x-rays showed good device placement, with restoration of disc height,

foraminal volume, and sagittal balance. All patients were up and walking

within 12 hours of surgery

CONCLUSIONS:Mid-term results of a laterally placed TDR device dem-

onstrate maintenance of pain relief and functional improvement. The ben-

efits of this technique – minimal morbidity, avoiding mobilization of the

great vessels, preserving the anterior longitudinal ligament, biomechani-

cally stable orientation, and broader revision options - suggest a promising

new direction for TDR procedures.

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

doi: 10.1016/j.spinee.2010.07.342

P67. A Comparative Study of Posterior Fixation in Acute Unstable

Thoracolumbar Injuries by Monoaxial and Polyaxial Pedicle Screws

Rajeshwar N. Srivastava, MD; King Georges Medical College, CSM

Medical University, Lucknow, India

BACKGROUND CONTEXT: The pedicle offers a strong point of at-

tachment of the posterior elements to the vertebral body and pedicle

ting and will be included with the post-meeting online content.