The spino-pelvic ratio: a novel global sagittal parameter associated with clinical outcomes in adult spinal deformity patients

International Spine Study Group (ISSG), Wesley M. Durand, Alan H. Daniels, David K. Hamilton, Peter Passias, Han Jo Kim, Themistocles Protopsaltis, Virginie LaFage, Justin S. Smith, Christopher Shaffrey, Munish Gupta, Michael Kelly, Eric Klineberg, Frank Schwab, Doug Burton, Shay Bess, Christopher Ames, Robert Hart

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Purpose: Analysis of interactions of spinal alignment metrics may uncover novel alignment parameters, similar to PI-LL. This study utilized a data-driven approach to hypothesis generation by testing all possible division interactions between spinal alignment parameters. Methods: This study was a retrospective cohort analysis. In total, 1439 patients with baseline ODI were included for hypothesis generation. In total, 666 patients had 2-year postoperative follow-up and were included for validation. All possible combinations of division interactions between baseline metrics were assessed with linear regression against baseline ODI. Results: From 247 raw alignment metrics, 32,398 division interactions were considered in hypothesis generation. Conceptually, the TPA divided by PI is a measure of the relative alignment of the line connecting T1 to the femoral head and the line perpendicular to the sacral endplate. The mean TPA/PI was 0.41 at baseline and 0.30 at 2 years postoperatively. Higher TPA/PI was associated with worse baseline ODI (p ' 0.0001). The change in ODI at 2 years was linearly associated with the change in TPA/PI (p = 0.0172). The optimal statistical grouping of TPA/PI was low/normal (≤ 0.2), medium (0.2–0.4), and high (' 0.4). The R-squared for ODI against categorical TPA/PI alone (0.154) was directionally higher than that for each of the individual Schwab modifiers (SVA: 0.138, PI-LL 0.111, PT 0.057). Conclusion: This study utilized a data-driven approach for hypothesis generation and identified the spino-pelvic ratio (TPA divided by PI) as a promising measure of sagittal spinal alignment among ASD patients. Patients with SPR ' 0.2 exhibited inferior ODI scores. Level of evidence: III.

Original languageEnglish
Pages (from-to)2354-2361
Number of pages8
JournalEuropean Spine Journal
Volume29
Issue number9
DOIs
StatePublished - Sep 1 2020

Keywords

  • Adult spinal deformity
  • Pelvic incidence
  • Sagittal alignment
  • T1 pelvic angle

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