1. Clinical correlation of SRS-Schwab Classification with HRQOL measures in a prospective non-US cohort of ASD patients
Dennis H. Nielsen, MD; Lars V. Hansen, MD; Casper R. Dragsted, MD; Martin Gehrchen, MD, PhD; Benny Dahl, MD, PhD, DMSci Spine Unit, Dept. of Orthopaedic Surgery, Rigshospitalet, Copenhagen University Hospital, Denmark

2. E-Poster #218 Clinical correlation of SRS-Schwab Classification…
Presenter: Dennis H. Nielsen (a) Globus Medical
Co-Authors: Lars V. Hansen No disclosures
Casper R. Dragsted No disclosures
Martin Gehrchen (a) Globus Medical, (a) Medtronic
Benny Dahl (a) Globus Medical, (a) Medtronic
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3. Introduction – Methods – Results – Discussion – References
The SRS-Schwab Adult Spinal Deformity Classification1 is regarded as an important communication tool for spine surgeons as it summarizes the complex pathology of ASD with four coronal curve types and three sagittal modifiers. For each of the sagittal modifiers the cutoff values separating level 0 from + have been proposed to predict severe disability defined by an Oswestry Disability Index (ODI) of more than 401,2. Purpose: The aim of the present study was to assess the clinical correlation of the sagittal modifiers with Health Related Quality of Life (HRQOL) measures in a prospective, consecutive non-US cohort of ASD patients.

4. SRS-Schwab Classification
Introduction – Methods – Results – Discussion – References
SRS-Schwab Classification
Coronal curve types (>30⁰) T: Thoracic only T/L: Thoracolumbar/Lumbar only D: Double curve N: No major coronal deformity
Sagittal modifiers
PI-LL
0: < 10⁰
+: 10 – 20⁰
++: >20⁰ PT
0: < 20⁰
+: ⁰
++: > 30⁰
Global alignment
0: SVA < 4 cm
+: SVA 4 – 9.5 cm
++ SVA > 9.5 cm
PI-LL = Pelvic Incidence minus Lumbar Lordosis
PT = Pelvic Tilt
SVA = Sagittal Vertical Axis

5. Introduction – Methods – Results – Discussion – References
Between March and August 2013 patients aged >18 years having sufficient long standing X-rays, prospectively answered the following questionnaires:
Oswestry Disability Index (ODI) EQ5D
VAS for back pain SF36v.1
SRS22r
The radiographs were uploaded to an online imaging system and assessed according to the SRS-Schwab classification system by one of two investigators.

6. Introduction – Methods – Results – Discussion – References
Statistics
The distribution of HRQOL scores were assessed using Quantile-Quantile (QQ) plots and the Shapiro-Wilk Normality test.
Homoscedasticity of within-group variance was assessed with Bartlett’s test.
For Normally distributed HRQOL scores (ODI, SRS22 total score and SF36 Physical Component Score (PCS)), the differences in means across sagittal modifier levels 0, + and ++ were assessed with one way ANOVA.
For non-Normally distributed HRQOL scores (VAS back pain and EQ5D index) the Kruskal-Wallis rank sum test was used.
Mean/rank differences between each pair of levels were not tested because of insufficient power caused by small sample size.
All statistics were calculated using R v (R Core Team, 2014)
P-values < 0.05 were considered significant

7. Introduction – Methods – Results – Discussion – References
112 patients participated.
Six patients were adult AIS patients
Seven had deformity surgery performed within 3 months
One had sagittal images impossible to classify.
Thus 14 patients were excluded
98 patients were included for analysis
median age was 64 years (range 18-85)
64% were female
49% had a history of previous deformity surgery
Distribution of the SRS-Schwab classification was as follows:
Curve type PI-LL PT Global alignment (SVA)
N (73%) 0 (53%) 0 (35%) 0 (35%)
L (14%) + (15%) + (41%) + (37%)
D (11%) ++ (32%) ++ (24%) ++ (28%)
T (2%)

8. Introduction – Methods – Results – Discussion – References
Table 1. Mean HRQOL Scores for 98 Consecutive Non-US Adult Patients with Spinal Deformity by Sagittal Modifier Grade According to the SRS-Schwab Classification
PI-LL PT
SVA + ++
ODI#
35.5
41.6
46.5
37.4
37.3
48.0
33.7*
39.7*
47.6*
SRS22r total score
3.2*
2.8*
2.6*
3.0*
3.1*
2.5*
3.1
3.0
2.7
VAS back pain#Ŧ
3.8*
4.5*
7.1*
3.5
4.5
7.3
4.1*
7.4*
EQ5D indexŦ
0.66*
0.65*
0.56*
0.59
0.66
0.56
0.32*
SF36 PCS
34.1*
30.9*
26.4*
33.1*
32.7*
25.5*
35.5*
30.5*
26.2*
PI-LL, Pelvic Incidence minus Lumbar Lordosis; PT, Pelvic Tilt; SVA, Sagittal Vertical Axis; ODI, Oswestry Disability Index; SRS, Scoliosis Research Society; VAS, Visual Analogue Scale, EQ, EuroQol; SF, Short Form; PCS, Physical Component Score; # lower scores means better quality of life; Ŧ median scores; * significant variation across modifier grades (P<0.05)

9. Introduction – Methods – Results – Discussion – References
Any classification system should be easy to use, classifying patients according to clinical impact with a high degree of reliability.
The SRS-Schwab Classification modifier cut offs were calculated using ODI scores1 and one previous study have shown significant variation of ODI and SF36 PCS across levels of all modifiers3.
Although we were only able to show significant variation of ODI across levels of SVA, all SRS-Schwab classification modifiers separated patients according to SF36 PCS in a consecutive non-US cohort of ASD patients.
The other HRQOL measures varied significantly across levels of two modifiers each (Table 1).

10. Introduction – Methods – Results – Discussion – References
The strengths of the current study were the prospective design and the consecutive cohort of ASD patients from a non-US tertiary referral institution.
The most significant weakness of the current study was the sample size, which prevented us from comparing each modifier level to one another (i.e. 0 vs. +, + vs. ++ and 0 vs. ++) due to low power.
We showed a difference in discriminative abilities of the HRQOL measures when applied to ASD patients grouped by SRS-Schwab sagittal modifiers. ODI scores was least discriminative with the variation being significant only across levels of SVA.
The small sample size could explain the non-significant variation of ODI across levels of PI-LL and PT.

11. Introduction – Methods – Results – Discussion – References
Schwab F, Ungar B, Blondel B, Buchowski J, Coe J, Deinlein D, et al. Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study. Spine May 20;37(12):1077–82.
Schwab FJ, Blondel B, Bess S, Hostin R, Shaffrey CI, Smith JS, et al. Radiographic Spino-pelvic Parameters and Disability in the Setting of Adult Spinal Deformity: A Prospective Multicenter Analysis. Spine [Internet] Mar 25;38(13):803–12.
Terran J, Schwab F, Shaffrey CI, Smith JS, Devos P, Ames CP, et al. The SRS-Schwab adult spinal deformity classification: assessment and clinical correlations based on a prospective operative and nonoperative cohort. Neurosurgery [Internet] Oct [cited 2014 Jan 13];73(4):559–68.
Smith JS, Klineberg E, Schwab F, Shaffrey CI, Moal B, Ames CP, et al. Change in Classification Grade by the SRS-Schwab Adult Spinal Deformity Classification Predicts Impact on Health-Related Quality of Life Measures: Prospective Analysis of Operative and Non-operative Treatment. Spine (Phila Pa 1976) [Internet] Jun 11 [cited 2013 Aug 12];38(19):1663–71.