95SProceedings of the NASS 22nd Annual Meeting / The Spine Journal 7 (2007) 1S–163S

PATIENT SAMPLE: A total of 10 patients with known sagittal imbal-

ance syndrome underwent bilateral TLIFs with cages correction. There

were seven women and three men in the study. The average age of the

patient was 52 years oldþ/-6 years.

OUTCOME MEASURES: The outcome measures used in the study were

radiographic evaluation and Oswetry outcome measures. The kyphotic an-

gle, coronal, and sagiital balance were measured preoperatively and

postoperatively.

METHODS: Ten patients underwent diskectomy of L5-S1 and bilateral

TLIF with multiple cages to correct sagittal imbalance syndrome. Follow

up took place at an average of 28 months (12–44).

RESULTS: The mean correction of the kyphotic angle at the L5-S1 level

was 22.9 �þ/-9.6 �. The average improvement in sagittal balance was

3.95þ/-.05 cm. The mean coronal balance improved 0.48þ/-1.4 cm. Esti-

mated blood loss during the procedure was 1,398þ/-738 mL. The Oswes-

try score improved from 42.1þ/-14.4 preoperatively to 20.3þ/-13.8

postoperatively. No deaths or permanent neurologic deficits occurred.

CONCLUSIONS: There are many factors to consider when deciding to

correct a sagittal imbalance deformity with multiple SPOs and a PSO.

The patient’s ability to tolerate substantial blood loss and the perceived ca-

pacity to undergo anterior exposure, all while achieving the desired

amount of correction are important factors. Our results demonstrated that

performing bilateral TLIFs with multiple cages can prove to be a useful

alternative in the correction of sagittal imbalance syndrome.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2007.07.242

P27. Cost-effectiveness of Interspinous Process Decompression for

Lumbar Spinal Stenosis: A Comparison with Conservative Care and

Laminectomy

Grant Skidmore, MD1, Stacey Ackerman, MSE, PhD2, Christopher Bergin,

MD3, Daniel Ross, MBA2, Jesse Butler, MD3, Manish Suthar, MD4,

Joshua Rittenberg, MD5; 1Neurological Specialists, Inc, Norfolk, VA, USA;2Covance Market Access Services Inc., San Diego, CA, USA; 3Illinois

Bone and Joint Institute, Ltd., Chicago, IL, USA; 4Pain Prevention and

Rehabilitation Center, St. Louis, MI, USA; 5Spine and Sports

Rehabilitation Center, Chicago, IL, USA

BACKGROUND CONTEXT: A gap in the continuum of care for lumbar

spinal stenosis (LSS) currently exists between conservative care and inva-

sive surgery. Interspinous Process Decompression (IPD) has been devel-

oped as a new minimally invasive treatment for LSS patients with

moderately impaired physical function. The clinical effectiveness of IPD

has been demonstrated in a randomized clinical trial to be superior to

continued conservative care and, based on our review of the published lit-

erature, roughly equivalent to laminectomy (LAMI). However, the cost-

effectiveness of IPD has not previously been investigated.

PURPOSE: The purpose of this study is to evaluate the cost-effectiveness

of IPD compared to conservative care and LAMI.

STUDY DESIGN/SETTING: Primary data were analyzed from a random-

ized clinical trial at 9 US sites comparing IPD (X STOP; St. Francis Med-

ical Technologies, Alameda, CA) versus conservative care with 2-year

follow-up. Data for LAMI come primarily from the published literature.

PATIENT SAMPLE: The trial included 69 IPD and 62 conservative care

patients (age 50þ) who were moderately impaired (baseline Zurich Claudi-

cation Questionnaire (ZCQ) physical function scoreO2) and had neurogenic

intermittent claudication secondary to imaging-confirmed LSS at 1 (72.3%)

or 2 (27.7%) levels. These patients had undergone at least 6 months of con-

servative care. The mean age was 69.8 years (70.2% were 65 years).

OUTCOME MEASURES: The incremental cost-effectiveness ratio (in 2006

US dollars) is calculated by dividing incremental direct medical costs by incre-

mental Quality Adjusted Life Years (QALYs). Medical technologies with

ratios less than $50,000 per QALY are generally considered cost-effective.

METHODS: Success rates are defined using the ZCQ criteria. QALYs are

calculated using patient-level SF-36 data from the trial that have been

transformed using the method of Nichol. Costs include first- and second-

line treatments, follow-up, and adverse events over two years. Unit costs

are based on the 2006 Drug Topics Redbook, 2006 Medicare Physician

Fee Schedule, and 2006 Medicare Provider Analysis and Review (MED-

PAR) data (representing 100% of Medicare inpatient payments).

RESULTS: For IPD patients treated in the inpatient setting, the incremen-

tal cost-effectiveness ratio relative to conservative care is $44,916 per QA-

LY, whereas, relative to LAMI, it is $22,175 per QALY. For outpatient

treatment with IPD, the ratios are $32,583 per QALY relative to conserva-

tive care and $3,879 per QALY relative to LAMI. The ratios fall within

a narrow range as key assumptions, such as patient age (!65 versus 65)

and number of levels treated (1 versus 2 levels) are varied. Comparatively,

these findings suggest that IPD is more cost-effective than lumbar discec-

tomy versus continued conservative care, which has a ratio estimated to be

around $51,000 per QALY. Of note, compared to LAMI, outpatient IPD is

nearly as cost effective as total hip replacement surgery (a well-established

cost-effective procedure, estimated at approximately $2,000 per QALY).

CONCLUSIONS: In patients with LSS treated with IPD, the clinical and

quality-of-life benefits yielded favorable cost-effectiveness ratios. These

results support the broader use of IPD to help address a substantial gap

in the continuum of care from conservative care to invasive surgery.

FDA DEVICE/DRUG STATUS: X STOP� Interspinous Process Decom-

pression System: Approved for this indication.

doi: 10.1016/j.spinee.2007.07.243

P28. Cutting C2 Bilaterally in Posterior Atlanto-axial Instrumented

Fixation: Answers to a Controversial Issue

Matthew Kang, MD1, Nicholas Post, MD1, Mary Ellen Costa2,

Joshua Marcus2, Maxim Koslow, MD1, Cooper Paul, MD1,

Anthony Frempong-Boadu, MD1; 1New York University, New York, NY,

USA; 2NY, USA

BACKGROUND CONTEXT: Resecting or preserving the C2 root in pos-

terior C1-C2 instrumented fixation is controversial in the literature. Goel et

al. was the first to publish favoring the resection of C2, but did not specif-

ically address potential C2 related disturbances in postoperative patient in-

terviews. Others have stated that resection of C2 has lead to debilitating

neuralgias. Preservation of C2 can result in neuralgia from a screw’s mass

effect. In the literature, the exact incidence of postoperative neuralgia,

using either technique, is unknown and reports are largely anecdotal.

PURPOSE: To look specifically at the postoperative status of patients’ C2

function and discusses other technical advantages when the C2 root is cut

in posterior C1-C2 instrumented fusion.

STUDY DESIGN/SETTING: Retrospective review of patients’ office and

hospital charts specifically looking at C2 nerve root function post C1-C2

posterior instrumented fusion and intraoperative blood loss. If necessary,

brief telephone interviews used to complete patient assessments.

PATIENT SAMPLE: Fifteen patients (mean age 70 yrs.) who underwent

C1-2 fixation, with C2 cut, from 2002–2007. Indications included: type 2

dens fracture, rheumatoid arthritis, spondylotic ligamentous laxity, os

odontoideum, and synovial cyst.

OUTCOME MEASURES: Postoperative incidence of C2 neuralgia after

cutting C2 in posterior C1-C2 instrumented fixation is analyzed. If present,

the degree of discomfort and debilitation to the patient is assessed by ques-

tionnaire. Also, quantitative measure of estimated blood loss in our patients

is compared with that of similar procedures, which spare C2, in the literature.

METHODS: Two surgeons, at a single hospital center, placed C1 lateral

mass and C2 pars screws in all patients under flouroscopic guidance. Thir-

teen patients underwent open technique and two patients had the instru-

mentation placed using a minimally invasive variation. Estimated blood

loss was recorded from the brief operative note and anesthesia records.

The follow up period ranged from postoperative day 1 to 20 months

96S Proceedings of the NASS 22nd Annual Meeting / The Spine Journal 7 (2007) 1S–163S

(average 7 months). Patient neurologic outcomes were measured using

office/hospital charts, direct examination, and/or telephone interview.

RESULTS: Excluding one patient lost to follow up, no one had a C2 dis-

turbance which affected everyday life. Outcomes ranged from intact C2

function to noticeable numbness on palpation without uncomfortable neu-

ralgias post procedure. Two patients had infections, one deep and one su-

perficial, both treated without further complications. Using a Medline

search, we noted up to a three-fold reduction in average blood loss when

compared to studies preserving C2 in similar procedures. There were no

failed fusions to date.

CONCLUSIONS: Cutting the C2 root can provide several operative advan-

tages and dramatically decrease blood loss in posterior C1-C2 instrumented

fixation without significant C2 resection related complaints post procedure.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2007.07.244

P29. Assessment of Age as Key Determinant of In-hospital Mortality,

Neurological Recovery, and Axonal Preservation in Spinal Cord

White Matter after Acute Traumatic Cervical Spinal Cord Injury

Julio C. Furlan, MD, MBA, MSC, PhD1, Michael G. Fehlings, MD, PhD,

FACS, FRCS(C)1; 1University of Toronto and University Health Network,

Toronto, Ontario, Canada

BACKGROUND CONTEXT: Despite an increasing incidence of spinal

cord injury (SCI) in the elderly, surprisingly little is known regarding neu-

rological outcomes in elderly with an acute SCI.

PURPOSE: This study was focused on the potential age-related differ-

ences on mortality, neurological recovery, and axonal preservation in spi-

nal cord white matter after acute traumatic cervical SCI.

STUDY DESIGN/SETTING: A retrospective cohort study and a histopath-

ological, immunocytochemical examination of postmortem spinal cord tissue.

PATIENT SAMPLE: The cohort study included all consecutive cases of

acute traumatic cervical SCI admitted from 1998–2000. The histopathological

study included all individuals with severe (motor complete) cervical SCI and

controls without neurotrauma from the TWH Spinal Cord Tissue Bank.

OUTCOME MEASURES: Mortality in the acute care SCI facility; neu-

rological recovery assessed by American Society Injury Association Im-

pairment Scale (AIS); number of axons within spinal cord tracts; and

area of degeneration.

METHODS: Younger individuals (age!65 years) were compared to elderly

subjects. In the cohort study, both groups were compared using Kaplan-

Meier curve and log rank test. Significant neurological recovery was defined

as improved AIS during the followup time. Gender and etiology of injury

(fall, MVA and others) were treated as potential confounders in a logistic

model. In the histopathological study, extent of degeneration was quantitated

after staining for myelin using luxol fast blue. Using NF200 immunostaining,

the number of axons within corticospinal tracts (CST), dorsal column (DC),

and lateral funiculus (LF) were quantitated from by image analysis.

RESULTS: In the cohort study, there were 23 elderly (10F, 13M; age 65–

89 years, mean, 40) and 28 younger individuals (4F, 24M; age 18–64

years, mean, 75). The distribution of severity of SCI was similar in both

groups (p50.116). Elderly and younger individuals with acute SCI were

not significantly different regarding survival in the acute SCI care facility

(p50.515) or neurological recovery post-SCI (p50.356). Analyzing a sub-

set of SCI individuals who were followed by a minimum of 6 months post-

injury (31/51), neurological recovery was unaffected by age (p50.502) or

gender (p50.208). However, there was a trend for an association between

neurological improvement and etiology of SCI (p50.064). The histopath-

ological study included 7 SCI individuals (2F, 5M; ages 31-82 years;

mean, 60) and 5 controls (2F, 3M; ages 30–73 years; mean, 51). Both

groups were comparable regarding age (p50.42) and gender distribution

(p51). SCI and control groups significantly differed regarding the number

of axons within CST (p!0.001) and LF (p50.004), but not DC (p50.201).

In the controls, the number of axons within CST, LF, and DC were not sig-

nificantly correlated with age/gender. There were no significant differences

between younger and elderly SCI individuals regarding the extent of

degeneration or the number of preserved axons.

CONCLUSIONS: Mortality in the acute stage after SCI and neurological

recovery post-injury are not significantly associated with age at injury. Al-

though neurological improvement was unaffected by age/gender, the etiol-

ogy of SCI might be associated with neurological recovery in the chronic

stage post-injury. The number of axons within spinal cord tracts was unaf-

fected by age in the controls and in the SCI group. Age does not appear to

affect the extent of degeneration post-SCI.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2007.07.245

P30. Outcomes of Patients at High Risk for Non-Union Undergoing

Reconstructive Spinal Surgery with Osteogenic Protein-1: A

Prospective Consecutive Cohort Study with Long Term Follow-up

Julio C. Furlan, MD, MBA, MSC, PhD1, Raja Rampersaud, MD,

FRCS(C)2, Eric M. Massicotte, MD, MSC, FRCS(C)2, Richard Perrin,

MD1, Yuriy Petrenko, MD3, Michael G. Fehlings, MD, PhD, FRCS(C),

FACS1; 1Krembil Neuroscience Centre, University Health Network and

University of Toronto, Toronto, Ontario, Canada; 2University Health

Network and University of Toronto, Toronto, Ontario, Canada; 3University

Health Network, Toronto, Ontario, Canada

BACKGROUND CONTEXT: The ability of osteogenic protein 1 (OP-1)

to induce bone formation has led to an increasing interest in its use in

fusion surgery.

PURPOSE: This prospective study examines the safety and efficacy of

OP-1 in patients deemed at high risk for developing a pseudoarthrosis fol-

lowing reconstructive spinal surgery.

STUDY DESIGN/SETTING: Prospective cohort study.

PATIENT SAMPLE: Patients at high risk for pseudoarthosis were defined

as those with connective tissue disorders, individuals with major medical

co-morbidities that could adversely affect bone healing, patients with his-

tory of previous failed fusions, and/or patients with limited availability or

poor quality of autogenous bone graft.

OUTCOME MEASURES: Outcome measures included adverse events,

radiographic fusion, the Oswestry Disability Index (ODI), and the SF-36

questionnaire.

METHODS: The SF-36 and ODI questionnaires were applied at baseline

(pre-operative evaluation) and at 3, 6, 12, 18, and 24 months following the

surgical OP-1 implant. The minimum clinically important differences were

based on previously reported data for the SF-36 (i.e. seven points in each

domain) and for the ODI (i.e. ten points). An independent musculoskeletal

radiologist reviewed all radiographs in a blinded manner. Radiographic in-

stability was defined as translation of larger than 2 mm and/or angulation

of larger than 5 � on post-operative flexion/extension x-rays. A solid fusion

was defined as evidence of bridging bone on radiographic evaluation. A

successful radiological outcome, therefore, was established if no radio-

graphic instability was observed along with radiological evidence of intact

instrumentation and evidence of osseous union. Gender, age and level of

spine disease (cervical/occipitocervical versus lumbar/lumbosacral) were

considered as potential covariates. Data were analyzed using Student’s

paired t-test and multiple logistic regression.

RESULTS: We included 17 males and 13 females with a mean age of 53

years (range 20–77 years) who were operated for cervical (n512) or lum-

bar pathology (n518) with a median postoperative followup of 24 months.

There was on average a 13% improvement (p50.001) in the mean postop-

erative ODI (39%64.6%) in comparison to the mean pre-operative ODI

(52%63.2%). This was paralleled by significant improvements in the

physical health (34.263 to 28.761.5; p50.015) and mental health

(43.762 to 47.563.1; p50.025) SF-36 scores. Twenty-six of the 30 pa-

tients were deemed to have a solid fusion. There were no allergic reactions

to OP-1 and no symptomatic hematomas.