133SProceedings of the NASS 27th Annual Meeting / The Spine Journal 12 (2012) 99S–165S

compressive modulus during static axial compression (466.76 6 77.63 vs.

476.76 6 110.03 N/mm2), or rotational stiffness (1.27 6 0.18 vs. 1.30 6

0.21 N-m/deg) between the six-screw and four-screw constructs. Static tor-

sion tests displayed increased maximum torque between the six-screw and

four-screw constructs (27.92 6 4.41 vs. 24.42 6 3.20 N-m). Surprisingly,

the six-screw construct exhibited decreased maximum load values com-

pared to the four-screw construct (2150.80 6 439.25 vs. 2471.00 6

612.31 N).

CONCLUSIONS: Index-level pedicle screws affect the short-segment

constructs, particularly in peak torque and maximum compressive load.

However, in terms of construct stiffness, index-level screws do not have

a statistically significant impact on short-segment pedicle screw constructs.

Furthermore, the polyurethane models implemented in this study have

been proven to be a viable option for future biomechanical testing. Given

the high variability of animal and cadaveric spines, these data are much

more consistent than those presented in previous studies. The nature of

the model allows for a more reliable comparison of spinal constructs.

Though the model is an attempt to mimic that of a human thoracolumbar

spinal segment, the results should not be taken as direct correlations to true

human cadaveric spines. Further testing must be conducted to assess the

validity of the burst fracture models.

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

any applicable devices or drugs.

http://dx.doi.org/10.1016/j.spinee.2012.08.349

P76. Analysis of Health-Related Quality of Life Improvements

Among Patients with Adult Spinal Deformity

International Spine Study Group1, Michael O’Brien, MD2, Richard Hostin,

MD2, Ian McCarthy, PhD3, Neil Fleming, PhD4, Gerald Ogola, MS4,

Rustam Kudyakov, MD, MPH4, Kathleen Richter, MS4, Rajiv Saigal, MD,

PhD5, Sigurd Berven, MD6, Vedat Deviren, MD5, Christopher P. Ames,

MD5; 1Brighton, CO, US; 2Southwest Scoliosis Institute, Plano, TX, US;3Baylor Health Care System, Plano, TX, US; 4Baylor University Medical

Center, Dallas, TX, US; 5University of California San Francisco, San

Francisco, CA, US; 6UCSF Department of Orthopaedic Surgery, San

Francisco, CA, US

BACKGROUND CONTEXT: Change in health related quality of life

(HRQOL) is a critical component in assessing the cost-effectiveness of sur-

gical treatment for adult spinal deformity (ASD), and there is reason to be-

lieve that changes in HRQOL vary according to patient demographics and

the pathology of ASD.

PURPOSE: Analyze the impact of demographic variables and pathology

of ASD on changes in HRQOL among patients receiving surgical treat-

ment for four categories of ASD: Primary Idiopathic Scoliosis (PIS), Pri-

mary Degenerative Scoliosis (PDS), Primary Sagittal Plane Deformity

(PSPD), and Revision (R).

STUDY DESIGN/SETTING: Multi-center, retrospective, consecutive

case series.

PATIENT SAMPLE: Three hundred twenty-three consecutive patients

undergoing surgical treatment for ASD.

OUTCOME MEASURES: HRQOL measures based on the Medical Out-

comes Study Short Form 36 (SF-36) physical and mental component

scores (PCS and MCS, respectively), the Oswestry Disability Index

(ODI), and the Scoliosis Research Society (SRS functional activity, pain,

self-image, and mental health scores) questionnaires after at least one year

following surgery.

METHODS: Patients ranged from 18 to 85 years of age, with an average

age of 54. Patients were assigned to one of four diagnostic categories based

on pre-operative radiographs and history: PDS (n559, 18%), PIS (n5102,

32%), PSPD (n539, 12%), and R (n5123, 38%). Statistical analysis in-

cluded paired t-tests, analysis of variance (ANOVA), and multivariate

regression.

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

RESULTS: Across all diagnostic categories, patients reported significant

improvement in all outcome measures except for SRS mental health:

SF-36 MCS (mean52.80; p!0.01), SF-36 PCS (5.98; p!0.01), ODI

(9.27; p!0.01), SRS functional activity (0.41; p!0.01), SRS self-image

(1.08; p!0.01), and SRS pain (0.88; p!0.01). No significant differences

in HRQOL improvements were observed across different categories of

ASD. ANOVA and multivariate regression results indicated a significant

(p!0.05) positive relationship between changes in HRQOL and age. Sim-

ilarly, multivariate regression results for a subset of patients with BMI data

(n5139) showed a significant (p!0.05) positive relationship between

changes in HRQOL and BMI.

CONCLUSIONS: Patients reported significant improvements in SF-36

MCS, SF-36 PCS, ODI, SRS functional activity, SRS self-image, and

SRS pain scores following surgical treatment for ASD. Improvements do

not appear to be dependent on the diagnostic category of deformity. Al-

though results differ somewhat across HRQOL measures, the analysis in-

dicates that older patients and patients with higher BMI may exhibit

significantly more improvement relative to younger patients and those with

lower BMI.

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

any applicable devices or drugs.

http://dx.doi.org/10.1016/j.spinee.2012.08.350

P77. Severity of Heterotopic Ossification in Relation to Cervical

Prosthesis Type and Surgery-Related Factors

David C. Noriega, MD1, Bel�en G. Medrano2, Jesus Manuel Cortes1,

Marina Martinez2, Ruben Hernandez1, Maria Plata, SA2, Mar�ıa Brotat3;1Valladolid, Spain; 2Hospital Clinico Universitario de Valladolid,

Valladolid, Spain; 3Madrid, Spain

BACKGROUND CONTEXT: As an alternative to fusion by arthrodesis,

the main goal of replacing a damaged cervical disc by an artificial prosthe-

sis is to restore and maintain mobility of the spinal segment.Heterotopic

ossification (HO) has been observed as an undesirable consequence of

the procedure as it reduces disc mobility.The reasons of HO are still poorly

understood.

PURPOSE: Analyze some factors that appear to be correlated with HO

frequency and severity and compared 3 different types of disc prosthesis.

STUDY DESIGN/SETTING: Retrospective analysis, local ethics comitte

approved.Severity of the HO was assessed through MacAfee score, on the

basis of CT and X-ray. Blindly and separately graded by 3 different profes-

sionals: radiologist, orthopedic surgeon and a spine surgeon.

PATIENT SAMPLE: Fifty-four patients, 26 men and 28 women, mean

age 48.3; range 37-74 years. Of these, 42 patients had surgery on one level

and 12 patients at two levels (IVLs), for a total of 66 implanted prosthesis.

Average follow-up was 44 months.Three artificial prosthesis (types A, B

and C) were used.

OUTCOME MEASURES: Sex, age, surgical time, postoperative bleed-

ing, surgery level, prosthesis type. The severity of the HO phenomenon

was assessed through use of the MacAfee score [1], established on the

basis of both CT and X-ray images. These were blindly – and separately

- graded by three different qualified professionals: a radiologist, an ortho-

pedic surgeon and a spine surgeon. 43.9% of the examined IVLs, HO

scores were the same whether based on CT or X-ray image grading.

51.5% of the examined IVLs, HO scores based on CT images showed

a higher severity, compared to scores based on X-rays.

METHODS: Statiscal analysis to evaluate correlation of HO with inde-

pendent and dependent variables and in beteween groups (sex, age, surgi-

cal level, prosthesis type, lengthof surgery).

RESULTS: CT results: no ossification 9.1%prosthesis (6 type A), HO

grade I 19.7%prosthesis (11 type A, 2 type B), HO grade II for 22.7% pros-

thesis (5 type A, 3 type B, 7 type C), HO grade III for 42.4% prosthesis (4

type A, 11 type B, 13 type C) HO gradeIV for 6.1% prosthesis (1 type A, 3

type B) X-ray results: no ossificationf 33.3% prosthesis (18 type A, 4 type

B), HO grade I for 21.2% prosthesis (4 type A, 4 type B, 6 type C), HO

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