The spino-pelvic ratio: a novel global sagittal parameter associated with clinical outcomes in adult spinal deformity patients.
European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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.
Neurosciences (Brain & Spine)
Orthopedics & Sports Medicine
Durand, Wesley M; Daniels, Alan H; Hamilton, David K; Passias, Peter; Kim, Han Jo; Protopsaltis, Themistocles; LaFage, Virginie; Smith, Justin S; Shaffrey, Christopher; Gupta, Munish; Kelly, Michael P; Klineberg, Eric; Schwab, Frank; Burton, Doug; Bess, Shay; Ames, Christopher; Hart, Robert A; and International Spine Study Group (ISSG), "The spino-pelvic ratio: a novel global sagittal parameter associated with clinical outcomes in adult spinal deformity patients." (2020). Articles, Abstracts, and Reports. 3247.