29SProceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

PURPOSE: Our goal is to confirm that primary intervertebral disc (IVD)

cells cultured in short-term monolayer is an appropriate system to test gene

therapy agents.

STUDY DESIGN/SETTING: Laboratory study.

PATIENT SAMPLE: N/A.

OUTCOME MEASURES: N/A.

METHODS: Adult bovine NP and AF cells cultured in monolayer were

transduced with adenoviruses expressing human bone morphogenetic

proteins (AdBMPs) or Sox9 (AdSox9). Chondrocyte phenotypic markers

(e.g., type II collagen and aggrecan) and the chondrocyte hypertrophy

marker (type X collagen) were measured six days after viral transduction

by reverse transcriptase chain reaction (RT-PCR).

RESULTS: Primary NP and AF cells transduced with AdBMPs, AdSox9,

or adenovirus expressing green fluorescence protein only (AdGFP, as con-

trol) continued to express healthy chondrocyte phenotypic markers and

showed no evidence of the expression of the chondrocyte hypertrophy

marker (type X collagen gene). Thus, we have shown that bovine NP

and AF cells transduced with adenovirus overexpressing 12 different

BMPs or Sox9 maintain their chondrocyte- or fibrocyte-like phenotype

in short-term culture.

CONCLUSIONS: In this study, primary bovine IVD cells transduced with

adenovirus overexpressing 12 BMPs or Sox9 preserved their phenotype in

short-term culture. These cells did not express the type X collagen gene,

an undesirable chondrocyte hypertrophic gene that could lead to ossification.

Therefore, low passage IVD cells cultured in monolayer is an appropriate

culture system to test therapeutic genes; these cells may also be appropriate

for engineering tissues or for cell therapy for degenerative disc diseases.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.068

Wednesday, November 11, 20095:10–6:10 PM

Focused Paper Presentations 4: Biomechanics

57. Biomechanical Importance of S1 and Iliac Fixation when

Instrumenting to the Pelvis: Analysis of Four Modern Lumbosacral

Fixation Techniques

John Tis1, Melvin Helgeson, MD2, Anton Dmitriev2, Ronald Lehman, Jr.,

MD2; 1Walter Reed Army Medical Center, Washington, DC, USA;2Washington, DC, USA

BACKGROUND CONTEXT: There has been no proven optimal method

for instrumenting across the lumbosacral junction and into the pelvis. As

a result, fixation to the pelvis is fraught with a higher rate of complications

and pseudarthrosis over other spinal arthrodesis procedures.

PURPOSE: We set out To evaluate the stabilizing potential of four tech-

niques of lumbosacral fixation: modified Galveston technique, iliac screws

connected caudal to S1, iliac screws connected cephalad to S1, and S2

screws without iliac screws.

STUDY DESIGN/SETTING: Bovine cadaveric lumbopelvic biomechan-

ical study.

PATIENT SAMPLE: Bovine Cadaveric Specimens.

OUTCOME MEASURES: N/A.

METHODS: Thirty two (n532) calf spines (L2-Sacrum/pelvis) were

tested under axial rotation, flexion/extension, and lateral bending. Groups

included: Group 1, Modified Galveston technique(no S1 fixation) (n58);

Group 2, S1 screws & iliac screws w/crosslinks distal to S1 (n58); Group

3, S1 screws and iliac screws w/crosslinkscephalad to S1 (n58); and

Group 4, S1 and S2 screws without iliac fixation (n58). Following non-de-

structive testing, specimens were fixed& flexed to failure, with peak failure

moment (Nm).

RESULTS: During ROM testing, all reconstructions significantly reduced

lumbosacral ROM under all methods of loading. There was a significant

increase in flexion/extension at L6-S1; without S1 fixation (Group 1) com-

pared to Groups 2–4. When crosslinks were not included, Group 3 had sig.

less ROM in axial rotation compared to Group 4 (S1,S2). Furthermore,

there was a trend towards decreased axial rotation ROM (p50.08) when

comparing Group 3 to Group 1. There were no sig. differences between

groups for lateral bending at L3-S1 or L6-S1. There was a sig. decrease

in ROM when crosslinks were added to the constructs in all 4 groups.

During destructive testing, peak failure moments for the different recon-

structions were 71.7 Nm, 65.4 Nm, 73.9 Nm, 32.2 Nm, respectively. Group

4 showed a sig. reduction in peak failure compared to Group 1 (p!0.001),

Group 2 (p50.001), and Group 3 (p!0.001). There was no significant

difference between Groups 1, 2, and 3 during destructive testing.

CONCLUSIONS: S1 screws are essential when instrumenting to the ilium.

S2 screws were inferior to iliac fixation (iliac screws or Galveston tech-

nique). Crosslinks significantly improve construct stiffness when placed near

the S1 sacral screws.

FDA DEVICE/DRUG STATUS: Pedicle Screws: Approved for this

indication.

doi: 10.1016/j.spinee.2009.08.070

58. Pelvic Radius Angle: An Essential Parameter for Sagittal

Spinopelvic Alignment

Roger Jackson, MD1, Anne McManus, RN2, Jill Moore2, Chris Hales2;1North Kansas City Hospital, North Kansas City, MO, USA; 2Midwest

Spine Foundation, North Kansas City, MO, USA

BACKGROUND CONTEXT: Evaluation of sagittal sacropelvic mor-

phology and its association with lumbopelvic alignment is important and

clinically relevant. Radiographic assessment of this morphology is often

difficult due to anatomic variation of the proximal sacrum. Consequently,

several different ways of measuring pelvic morphology are used today.

PURPOSE: Provide an efficient and user friendly methodology to evalu-

ate standing sagittal profile and define minimum requirements for lordosis.

The approach should eliminate registration of the sacral endplate yet still

convey important clinical information.

STUDY DESIGN/SETTING: Evaluation of measurements for lumbopel-

vic alignments on standing 36’’ lateral radiographs.

PATIENT SAMPLE: 200 asymptomatic adult volunteers. A clinically

relevant group of 24 high grade lytic spondylolisthesis patients was used

to determine both efficiency and reliability of the pelvic morphology mea-

surements for 2 different methodologies.

OUTCOME MEASURES: Means, standard deviations and ranges were

calculated. Statistical correlations for the measurement parameters were

computed. For the patient films, time to complete the morphology mea-

surements as well as intra- and inter-observer reliabilities for these mea-

surements were determined by and compared between 3 observers.

METHODS: Pelvic Lordosis (PL) was measured from the Pelvic Radius

(PR) line, originating at the Pelvic Hip Axis, to the S1 endplate and the

Pelvic Radius Angle (PRA), another primary parameter of pelvic morphol-

ogy as well as balance around the hips, was measured from the PR line to

the horizontal, as all previously defined in the literature. Pelvic Incidence

(PI) was determined. Vertebral endplate slopes (VES) were measured from

the horizontal up (þ) or down (-) to a vertebral body endplate tangent line.

Total lordosis (T12-S1) was measured by the Cobb method from the infe-

rior T12 endplate to the superior S1 endplate. The following 2 equations

were evaluated: PRA 5 sacral endplate slope (SES) þ PL (fixed pelvic

contribution to lordosis), wherein neither SES or PL needed to be directly

measured; and combined Lumbo-Pelvic Lordosis (LPL) 5 PRA 6 a spe-

cific VES. In the patients, PRA and PI were studied so that both efficiency

and reliability of their measurements could be compared.

RESULTS: PRA was approximately 70�, but always !90� and O55�;Total lordosis was more variable (34� to 80�), however Total LPL

(PRA þ T12 VES) was approximately 90� and always O70�; Distal LPL

30S Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

(PRA 6 L4 VES) was always 45�; L4 VES was approximately neutral

(range: 16� to -24�); T12 VES was always positive (4� to 37�); PI was

approximately 55� (range 31� to 80�) and PRA was better correlated with

the lordosis measurements (r5-.72) compared to PI (r5-.52). In the

volunteers, intra- and inter-observer reliabilities were very high for both

PRA and PI measurements (r .95 for all). When applied clinically in the

patients, intra- and inter-observer reliabilities were better for PRA vs. those

for PI (r5.93 and .89 vs. r5.79 and .68, respectively). Measurement of

PRA was 50% faster than PI.

CONCLUSIONS: PRA and VES can determine minimum lordosis

requirements, which are dependent on individual pelvic morphology, with-

out having to identify the entire sacral endplate. This methodology, based

on the PR technique, can be both efficiently and reliably applied in the

clinical setting of any spinal practice. When fixing the lordosis by surgical

fusion, minimum requirements should be met.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.071

59. The Effect of Sagittal Alignment on Posterior Fixation at the

Cervicothoracic Junction

Thomas Sylvester, MD1, Alexander Ghanayem, MD1, Susan Renner, PhD2,

Leonard Voronov, MD, PhD2, Braden McIntosh2, Gerard Carandang2,

Robert Havey, MS2, Dongkeun Lee2, Anastasios Dimitriadis, MD2,

Avinash Patwardhan, PhD2; 1Loyola University Chicago, Maywood, IL,

USA; 2Hines VA Hospital, Hines, IL, USA

BACKGROUND CONTEXT: Traumatic injuries at the cervicothoracic

junction are common injuries with reported incidences as high as 9% in

spinal cord injured patients. Fixation at this level is challenged by the ana-

tomical transition from the flexible, lordotic cervical spine to the rigid, ky-

photic thoracic spine. Much data has been published regarding the

adequacy of varying lengths of anterior, posterior and combined fusion con-

structs. However, there has been no data regarding the influence of sagittal

alignment on posterior cervicothoracic stabilization.

PURPOSE: The purpose of this study is to characterize the effect of

sagittal alignment on a posterior fusion for a two column cervicothoracic

junction injury.

STUDY DESIGN/SETTING: Biomechanical Laboratory Study.

PATIENT SAMPLE: Cadaveric specimens.

OUTCOME MEASURES: N/A.

METHODS: Eight fresh-frozen cadaveric spine specimens (levels C5-T1,

age 49.8þ/8.4 years) were cleaned of soft tissue, leaving the ligamentous

structures intact. Each specimen was radiographed to rule out obvious

deformity or malignancy. Pedicle screws were placed bilaterally at C7

and T1. Follower load guides were secured to C6 and C7. C5 and T1 were

secured proximally and distally in PMMA. The intact specimen was com-

pressed to 150 N using the follower load technique. The load path at C7-T1

was then varied in the anterior-posterior plane to simulate a change in

kyphotic sagittal alignment at the C7-T1 disc space from the follower load

alignment (0 degrees) to a relative kyphotic alignment (40 degrees). This

procedure was then repeated for each specimen with a C7-T1 posterior

two column injury with and without posterior fixation in place. C7-T1 seg-

mental angular and translational motion was measured using both opto-

electronic instrumentation and digital fluoroscopy. Comparisons (t-test)

were then made between the follower load alignment and the increased

kyphotic alignment.

RESULTS: Analysis of the eight tested specimens demonstrated that in-

creased kyphosis at the C7-T1 disc space significantly increased C7-T1 an-

terior slip from 0.8760.85% to 2.0461.91% (p50.03) and angular motion

from 0.2060.52 degrees to 1.3861.08 degrees (p50.03) in the posterior

two-column injury model. Increased kyphosis also significantly increased

C7-T1 angular motion in the intact spine from 0.5060.35 degrees to

2.3661.56 degrees (p50.03). Increased kyphosis with posterior fixation

for the two-column injury did not significantly affect the C7-T1 anterior

slip (0.4860.47% vs. 0.6861.78%, p52.39) or angular motion

(0.8260.50 degrees vs. 0.5360.32 degrees, p50.23).

CONCLUSIONS: Increasing sagittal alignment, or kyphosis, at the cervi-

cothoracic junction is related to several factors such as normal variation in

upper thoracic spine alignment and the relative changes in posture that

occur with natural aging. As our population ages, issues of fixation and

sagittal alignment in cervicothoracic trauma become an important consid-

eration. This data suggests that C7-T1 single level posterior fixation of

a two column cervicothoracic junction injury, using a pedicle screw-rod

construct may be sufficient to resist significant angular motion and trans-

lation at that level. While our study applies only to the immediate stability

of the spine after injury and fixation, our data suggest that our fixation

model provides a stable environment for the formation of bony fusion.

Further studies are necessary to study long term implications of sagittal

alignment on posterior cervicothoracic fixation.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.072

60. Impact of Degenerative Changes of Soft Tissue Structures on

Motion at Diseased and Adjacent Levels in Lumbar

Spondylolisthesis as Assessed with Kinetic MRI

Scott Daffner, MD1, Kent Sheridan2, Min Ho Kong, MD2, Jeffrey Wang,

MD3; 1West Virginia University, Morgantown, WV, USA; 2University of

California, Los Angeles, Los Angeles, CA, USA; 3University of California,

Los Angeles, Santa Monica, CA, USA

BACKGROUND CONTEXT: Pathologic changes associated with the de-

velopment of degenerative lumbar spondylolisthesis include degeneration of

the intervertebral disc, facet joint arthrosis, ligamentum flavum hypertrophy,

interspinous ligament degeneration, and paraspinal muscle fatty atrophy.

Prior studies of lumbar kinematics in this condition have relied almost exclu-

sively on plain radiographic assessment of motion or cadaveric experiments.

Kinetic MRI (kMRI) allows accurate measurement of spinal segmental

motion while also permitting assessment of associated soft tissue structures.

To date, no studies have reported the in vivo role of these soft tissue structures

in segmental motion in lumbar spondylolisthesis.

PURPOSE: To assess segmental motion at spondylolisthetic and adjacent

levels based on the degree of degenerative changes of associated soft tissue

structures.

STUDY DESIGN/SETTING: In vivo imaging study of human lumbar

spinal kinematics.

PATIENT SAMPLE: 113 patients with single-level Grade 1-2 degenera-

tive spondylolisthesis at L3-4, L4-5, or L5-S1 and 307 patients with symp-

tomatic back or leg pain but no spondylolisthesis.

OUTCOME MEASURES: Angular and translational segmental motion

at diseased and adjacent segments.

METHODS: All patients underwent weightbearing kMRI of the lumbar

spine in neutral, 30� of flexion, and 20� of extension. Mid-sagittal T2 W

images were evaluated. Digital imaging software determined values of

translational motion (TM) and angular motion (AM) through the range

of motion. An experienced spine surgeon graded the degree of disc degen-

eration (DDD), facet degeneration (FD), ligamentum flavum hypertrophy

(LF), interspinous ligament degeneration (IS), and paraspinal muscle fatty

atrophy (PSM) based on previously described scoring systems. Motion

values at the diseased and adjacent segments were compared to degenera-

tive change grades at the diseased level as well as to control values

obtained for patients with degenerative changes at corresponding levels

who did not have spondylolisthesis.

RESULTS: As DDD grade increased, TM at diseased levels increased

whereas TM at adjacent levels decreased. AM slightly increased initially

then decreased at diseased levels, whereas adjacent levels showed a steady

decrease in AM. As FD increased, TM slightly increased at diseased and

adjacent levels; AM steadily decreased. With LF hypertrophy, TM in-

creased and AM remained stable with L3-4 and L4-5 spondylolisthesis,