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

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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.

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Funding

This study was supported by the ISSG Foundation.

Author information

Authors and Affiliations

  1. Warren Alpert Medical School of Brown University, Providence, RI, USA

    Wesley M. Durand

  2. Department of Orthopaedic Surgery, Warren Alpert Medical School of Brown University, 1 Kettle Point Avenue, East Providence, RI, 02914, USA

    Alan H. Daniels

  3. University of Pittsburgh Medical Center, Pittsburgh, PA, USA

    David K. Hamilton

  4. Department of Orthopedics, NYU Langone Orthopedic Hospital, New York, NY, USA

    Peter Passias & Themistocles Protopsaltis

  5. Hospital for Special Surgery, New York, NY, USA

    Han Jo Kim, Virginie LaFage & Frank Schwab

  6. University of Virginia Health System, Charlottesville, VA, USA

    Justin S. Smith

  7. Duke University, Durham, NC, USA

    Christopher Shaffrey

  8. Washington University, St. Louis, MO, USA

    Munish Gupta & Michael P. Kelly

  9. University of California-Davis, Sacramento, CA, USA

    Eric Klineberg

  10. University of Kansas Hospital, Kansas City, KS, USA

    Doug Burton

  11. Denver International Spine Center, Denver, CO, USA

    Shay Bess

  12. University of California-San Francisco, San Francisco, CA, USA

    Christopher Ames

  13. Swedish Neuroscience Institute, Seattle, WA, USA

    Robert Hart

Authors
  1. Wesley M. Durand
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  2. Alan H. Daniels
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  3. David K. Hamilton
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  7. Virginie LaFage
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  12. Eric Klineberg
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  13. Frank Schwab
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  14. Doug Burton
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  15. Shay Bess
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  16. Christopher Ames
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  17. Robert Hart
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Consortia

International Spine Study Group (ISSG)

Corresponding author

Correspondence to Alan H. Daniels.

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Author-specific potential conflicts of interest have been detailed in the conflict of interest disclosure.

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This study was approved by IRBs at participating institutions.

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Durand, W.M., Daniels, A.H., Hamilton, D.K. et al. The spino-pelvic ratio: a novel global sagittal parameter associated with clinical outcomes in adult spinal deformity patients. Eur Spine J 29, 2354–2361 (2020). https://doi.org/10.1007/s00586-020-06472-x

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  • DOI: https://doi.org/10.1007/s00586-020-06472-x

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