48S Proceedings of the NASS 24th Annual Meeting / The Spine Journal 9 (2009) 1S-205S

during level walking, and muscular activity measured during stationary flex-

ion, extension, and lateral bending using surface EMG (Noraxon, Scottsdale,

AZ). Standard t-test was used to determine significance (p!0.05).

RESULTS: There was a trend towards increased gait velocity and in-

creased cadence in fused patients. Torso displacement in the sagittal plane

was increased whereas truncal rotation was decreased post-fusion as com-

pared to normal subjects. Significant reduction in pelvic tilt, as well as hip

and knee ROM in both stance and swing phase were measured post-fusion

(P!0.05). Dramatic reductions of the area, mean, and peak values of each

EMG phase (flexion and relaxation) were seen in trapezius, latissimus dor-

si, and multifidus activity during forward flexion, extension, and lateral

bending in post-operative patients (p!0.05).

CONCLUSIONS: Overall, patients who have undergone posterior spinal

fusion for idiopathic scoliosis demonstrate significantly altered gait pat-

terns as well as diminished paraspinal muscular recruitment during spinal

motions. Further study is required to determine if these altered mechanics

result in clinically significant musculoskeletal complications after fusion.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.112

Thursday, November 12, 20094:00–5:00 PM

Concurrent Session 1: Health Policy

91. Direct Economic Impact of Posterior Minimally Invasive

Decompression and Fusion Compared to Conventional Open for

Spondylolisthesis

Randolph Gray, MBBS, FRACS1, Michael Fehlings, MD, PhD, FRCS(C),

FRCS2, Eric Massicotte, MD, MSC, FRCSC2, Stephen Lewis, MD, FRCS,

MSC2, Raja Rampersaud, MD, FRCS(C)2; 1Krembil Neuroscience Centre,

Toronto Western Hospital, Toronto, Ontario, Canada; 2University of

Toronto, Toronto, Ontario, Canada

BACKGROUND CONTEXT: The utility of Minimally Invasive Fusion

(MIS) remains controversial. Reduced acute surgical morbidity has been

shown for MIS technique, however concerns such as limited comparative

outcomes studies, learning curve, the potential for increased complications

and increased cost, MIS techniques they have not been widely adapted or

accepted within the surgical spine community. To date the impact of cost

has not been formally assessed with a comparable control group.

PURPOSE: The objective of this study was to compare the peri-operative mor-

bidity and direct economic impact of one or two level primary decompression

and fusions for low grade (I-II) degenerative or isthmic spondylolisthesis using

a minimally invasive surgical (MIS) vs. conventional open techniques.

STUDY DESIGN/SETTING: Retrospective review of prospectively col-

lected data, in a spinal unit comprising of four-experienced fellowship

trained spinal surgeons.

PATIENT SAMPLE: 78 consecutive patients with a mean age of 57.12

(range 22–81) years, undergoing one or two level spinal fusion for spondy-

lolisthesis in the one institution were included in the study.

OUTCOME MEASURES: In-hospital micro-costing data including OR,

nursing, imaging, labs, pharmacy and allied health cost was utilized. The

peri-operative outcome measures of Length of Stay, OR time, intra opera-

tive blood loss, change in haemoglobin, and complications were also in-

cluded in the study.

METHODS: A retrospective cohort study was performed using prospective

data from 78 consecutive patients (n5 37 [MIS -one surgeon]/n541 [open -

three surgeons]) between 2005 and 2008 in a single institution froma completely

socialized health care system. All 4 surgeons had at least 5 years of experience

with the fusion techniques studied. Independent review was performed.

RESULTS: The groups were comparable in age, sex, pre-operative hemo-

globin (Hb), ASA, Charlson co-morbidity index, BMI and levels fused. All

MIS patients had an inter-body cage(s) compared to only 14 in open group.

Blood loss (206 vs. 798mls), transfusions (0 vs. 17%) and length of stay

(5.9 vs. 8.6 days) were significantly (p!0.01) lower in the MIS group.

Complications were also less in the MIS group (MIS: durotomy(1),

UTI(3)/Open: durotomy (3), UTI(8), neurodeficit(1)). Average cost of an

open fusion was 1.28 times greater then cost of a MIS fusion

(p50.001). There was a significant positive correlation between the length

of stay and cost of surgery (Open p5 0.001, MIS p50.01). Patient age,

BMI or instrumentation did not have a significant influence on the cost.

CONCLUSIONS: This matched cohort study demonstrates reduced acute

postoperative morbidity and a 28% reduction in direct institutional cost as-

sociated with MIS lumbar fusion compared to open. This study refutes the

common perception of high costs associated with minimally invasive fu-

sion and supports reduced acute surgical morbidity.

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

any applicable devices or drugs.

doi: 10.1016/j.spinee.2009.08.114

92. Clinical Outcomes in Worker’s Compensation Patients: A Case-

Control Study

Leah Carreon, MD, MSC, Steven Glassman, MD, Mladen Djurasovic, MD,

John Johnson, MD, Rolando Puno, MD, Mitchell Campbell, MD,

John Dimar, II, MD; Leatherman Spine Center, Louisville, KY, USA

BACKGROUND CONTEXT: Previous studies have demonstrated poor

outcomes in patients receiving workers compensation after lumbar fusion.

However, a case-control study where patients are matched for covariates

known to affect outcomes after lumbar fusion including baseline clinical

outcome measures has not been done.

PURPOSE: To compare clinical outcomes after lumbar fusion in patients

receiving worker’s compensation to a case-matched control group who are

not on worker’s compensation.

STUDY DESIGN/SETTING: Case-control propensity matched.

PATIENT SAMPLE: 58 matched pairs of worker’s compensation:non-

worker’s compensation patients who underwent posterolateral lumbar

fusion.

OUTCOME MEASURES: Oswestry Disability Index (ODI), Short Form

36 (SF-36), Back and Leg pain numeric rating scales.

METHODS: From 783 patients who underwent posterolateral fusion with

complete pre-operative and two-year post-operative outcome measures, 60

patients who were receiving worker’s compensation were identified. Pro-

pensity scoring technique was used to match these patients to a control

group not receiving worker’s compensation using gender, age, smoking

status, BMI, diagnosis, number of levels fused, pre-operative ODI, SF-

36 PCS (Physical Composite Summary), SF-36 MCS (Mental Composite

Summary), back and leg pain scores producing 58 matched pairs.

RESULTS: There were no significant differences between the demograph-

ics and pre-operative outcome scores in the two groups. At two-years post-

operative, patients not receiving worker’s compensation had a significantly

greater improvement in ODI, SF-36 PCS and back pain scores compared to

those receiving worker’s compensation. The mean two year ODI, SF-36

PCS and back pain raw scores of patients receiving worker’s compensation

were significantly lower than those not receiving worker’s compensation.

11 of 58 (19%) patients receiving worker’s compensation achieved mini-

mum clinically important difference (MCID) in terms of ODI (ODI12.8)

compared to 21 of 58 (36%) of those not receiving worker’s compensation

(p50.061). Only 5 of 58 (9%) patients receiving worker’s compensation

achieved substantial clinical benefit (SCB) in terms of ODI (ODI18.8)

compared to 19 of 58 (33%) of those not receiving worker’s compensation

(p50.002). Only 9 of 58 (16%) patients receiving worker’s compensation

achieved SF-36 PCS MCID (PCS4.9) compared to 23 of 58 (40%) of those

not receiving worker’s compensation (p50.006). Only 7 of 58 (12%) pa-

tients receiving worker’s compensation achieved SF-36 PCS SCB

(PCS6.2) compared to 21 of 58 (36%) of those not receiving worker’s com-

pensation (p50.004).