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

International Spine Study Group (ISSG)

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


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


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

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine


Dive into the research topics of 'The spino-pelvic ratio: a novel global sagittal parameter associated with clinical outcomes in adult spinal deformity patients'. Together they form a unique fingerprint.

Cite this