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Published in: European Spine Journal 11/2023

22-09-2023 | Pseudarthrosis | Original Article

L1-pelvic angle: a convenient measurement to attain optimal deformity correction

Authors: Hani Chanbour, William Hunter Waddell, Justin Vickery, Matthew E. LaBarge, Andrew J. Croft, Michael Longo, Steven G. Roth, Jeffrey M. Hills, Amir M. Abtahi, Scott L. Zuckerman, Byron F. Stephens

Published in: European Spine Journal | Issue 11/2023

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(1) Evaluate the associations between L1-pelvic angle (L1PA) and both sagittal vertical axis (SVA) and T1-pelvic angle (T1PA), and (2) assess the clinical impact of L1PA.


A single-institution retrospective cohort study was undertaken for patients undergoing adult spinal deformity (ASD) surgery from 2013 to 2017. Ideal L1PA was defined as (0.5xPelvic Incidence)-21. Pearson correlation was performed to compare L1PA, SVA, and T1PA. Univariate/multivariate regression was performed to assess the effect of L1PA on mechanical complications, controlling for age, BMI, and postoperative pelvic incidence-lumbar lordosis mismatch (PI/LL). Due to the overlapping nature of patients with pseudarthrosis and rod fracture, these patients were analyzed together.


A total of 145 patients were included. Mean preoperative L1PA, SVA, and T1PA were 15.5 ± 8.9°, 90.7 ± 66.8 mm, and 27.1 ± 13.0°, respectively. Mean postoperative L1PA, SVA, and T1PA were 15.0 ± 8.9°, 66.7 ± 52.8 mm, and 22.3 ± 11.1°, respectively. Thirty-six (24.8%) patients achieved ideal L1PA. Though the correlation was modest, preoperative L1PA was linearly correlated with preoperative SVA (r2 = 0.16, r = 0.40, 95%CI = 0.22–0.60, p < 0.001) and T1PA (r2 = 0.41, r = 0.62, 95%CI = 0.46–0.76, p < 0.001). Postoperative L1PA was linearly correlated with postoperative SVA (r2 = 0.12, r = 0.37, 95%CI = 0.18–0.56, p < 0.001) and T1PA (r2 = 0.40, r = 0.62, 95%CI = 0.45–0.74, p < 0.001). Achieving ideal L1PA ± 5° was associated with a decreased risk of rod fracture/pseudarthrosis on univariate and multivariate regression (OR = 0.33, 95%CI = 0.12–0.86, p = 0.024). No association between achieving ideal L1PA and patient-reported outcomes was observed.


L1PA was modestly correlated with SVA and T1PA, and achieving ideal L1PA was associated with lower rates of rod fracture/pseudarthrosis. Future studies are warranted to better define the clinical implications of achieving a normal L1PA.

Level of evidence

L1-pelvic angle: a convenient measurement to attain optimal deformity correction
Hani Chanbour
William Hunter Waddell
Justin Vickery
Matthew E. LaBarge
Andrew J. Croft
Michael Longo
Steven G. Roth
Jeffrey M. Hills
Amir M. Abtahi
Scott L. Zuckerman
Byron F. Stephens
Publication date
Springer Berlin Heidelberg
Published in
European Spine Journal / Issue 11/2023
Print ISSN: 0940-6719
Electronic ISSN: 1432-0932

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