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Combined Assessment of Pelvic Tilt, Pelvic Incidence/Lumbar Lordosis Mismatch and Sagittal Vertical Axis Predicts Disability in Adult Spinal Deformity: A Prospective Analysis: PAPER #20*

Schwab, Frank J. MD; Bess, Shay MD; Blondel, Benjamin MD; Hostin, Richard MD; Shaffrey, Christopher I. MD; Smith, Justin S. MD, PhD; Boachie‐Adjei, Oheneba MD; Burton, Douglas C. MD; Akbarnia, Behrooz A. MD; Mundis, Gregory M. MD; Ames, Christopher P. MD; Kebaish, Khaled; Hart, Robert A. MD; International Spine Study Group; Lafage, Virginie PhD

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Summary: Sagittal spinal malalignment (SSM) is commonly defined by increased sagittal vertical axis (SVA), however SVA alone may underestimate the severity of SSM. Spino‐pelvic parameters provide a more complete assessment of SSM. Multi‐center, prospective analysis of consecutively enrolled adult spinal deformity patients demonstrated pelvic tilt (PT) and pelvic incidence/lumbar lordosis mismatch (PI‐LL) combined with SVA predict patient disability and provide a guide for patient assessment. Threshold values for severe disability (ODI≥40) included: PT≥22°, SVA ≥46mm, and PI‐LL≥11°.

Introduction: Sagittal spinal malalignment (SSM) is commonly defined by increased sagittal vertical axis (SVA), however, SVA alone may underestimate the severity of SSM. Spino‐pelvic parameters provide a more complete assessment of SSM. Little data has correlated spino‐pelvic parameters with disability. Purpose: evaluate correlations between sagittal spino‐pelvic parameters and health related quality of life (HRQOL) scores.

Methods: Demographic, radiographic, and HRQOL data were obtained from patients consecutively enrolled into a multi‐center, prospective study evaluating operative (OP) vs. nonoperative (NON) treatment for adult spinal deformity (ASD). Inclusion criteria: age >18 years and radiographic diagnosis of ASD (scoliosis >20°, or SVA > 5cm, or pelvic tilt > 25°, or thoracic kyphosis > 60°). Radiographic evaluation: frontal and lateral spino‐pelvic measurements. HRQOL questionnaires: Oswestry Disability Index (ODI), Scoliosis Research Society Questionnaire (SRS‐22r). Radiographic parameters were correlated with HRQOL values. Radiographic parameters demonstrating highest correlation with HRQOL values were evaluated to determine a disability threshold of ODI≥40.

Results: Between 10/2008 to 12/2010, 492 consecutive ASD patients (mean age 51.9 years, SD 16.8) were enrolled. Patients treated OP (n=178) were older (55 vs. 50.1 years, p<0.05), had greater SVA (5.5 vs. 1.7cm, p<0.05), greater pelvic tilt (PT; 22° vs. 11°, p<0.05) and greater pelvic incidence/ lumbar lordosis mismatch (PI‐LL; 12.2 vs. 4.3; p<0.05) than NON (n=314). OP demonstrated greater disability on all HRQOL measures compared to NON (ODI =41.4 vs. 23.9, p<0.05; SRS total=2.9 vs. 3.5, p<0.05). Pearson analysis demonstrated PT, SVA, and PI‐LL correlated most strongly with disability for both OP and NON patients (p<0.001). Linear regression models demonstrated threshold radiographic spino‐pelvic parameters for ODI≥40 included: PT≥22° (r=0.38), SVA ≥46 mm (r=0.47), PI‐LL≥11 (r=0.45).

Conclusion: SSM is a disabling condition. Prospective analysis of consecutively enrolled ASD patients demonstrated PT and PI‐LL combined with SVA predict patient disability and provide a guide for patient assessment. Threshold values for severe disability included: PT≥22°, SVA ≥46mm, and PI‐LL≥11°.

© 2011 Lippincott Williams & Wilkins, Inc.

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