European Spine Journal

, Volume 28, Issue 12, pp 3066–3075 | Cite as

A critical thoracic kyphosis is required to prevent sagittal plane deterioration in selective thoracic fusions in Lenke I and II AIS

  • Dominique A. RothenfluhEmail author
  • Alexandra Stratton
  • Colin Nnadi
  • Nicolas Beresford-Cleary
Original Article



Thoracic hypokyphosis following AIS correction may be associated with reduced lumbar lordosis with potential adverse effects on the global sagittal balance. In the present study, we were interested in how the amount of thoracic kyphosis influences the sagittal profile and balance in selective thoracic (STF) and thoracolumbar fusions.


Out of 154 patients, 86 patients had correction of AIS Lenke I or II with a side-loading pedicle screw system and completed a 2-year follow-up. Patient factors such as age, Risser grade, lowest and upper instrumented vertebra, and lumbar modifier were recorded. Coronal Cobb and sagittal parameters were measured using Surgimap. Statistical analysis according to distributions and multiple linear and logistic regressions was performed using STATA for Mac v13.


In STF, logistic regression against post-operative change in SVA versus thoracic kyphosis allowed calculation of a critical thoracic kyphosis of 23° (ROC AUC 0.65, spec 0.70, sens 0.63), below which deterioration of the sagittal vertical axis is more likely (PPV 71.4%). Patients with hypokyphosis exhibited an increase in the SVA (pre-operative 7.2 ± 37.1 mm vs. 23.1 ± 27.6 mm at 2 years, p = 0.0164), whereas it was maintained from pre-operative to 2 years post-operative if thoracic kyphosis is above 23° (pre-operative 2.5 ± 28.9 mm vs. 5.4 ± 26.9 mm at 2 years, p = 0.579).


A critical thoracic kyphosis of 23° and more should be aimed for in hypokyphotic patients to potentially avoid post-operative sagittal plane deterioration with mechanical and likely also clinical consequences.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material.


Adolescent idiopathic scoliosis Hypokyphosis Sagittal plane Thoracic kyphosis 


Compliance with ethical standards

Conflict of interest

The authors declare no conflicts of interest related to this work.

Supplementary material

586_2019_6093_MOESM1_ESM.pptx (188 kb)
Supplementary material 1 (PPTX 188 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Oxford University Hospitals NHS Foundation TrustNuffield Orthopaedic CentreOxfordUK
  2. 2.Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), Botnar Research CentreUniversity of OxfordOxfordUK
  3. 3.The Ottawa HospitalUniversity of OttawaOttawaCanada

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