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Scoliosis flexibility correlates with post-operative outcomes following growth friendly surgery



The purpose of this study was to determine the relationship between pre-operative scoliosis flexibility and post-operative outcomes, including curve correction and complications, for patients who have been treated with growth friendly surgery (GFS) for early onset scoliosis (EOS).


The study was conducted as a retrospective review of prospectively collected data from an international, multicenter, EOS database. EOS patients with pre-operative flexibility radiographs (traction or bending) were identified. Pre-operative flexibility and immediate post-operative correction were calculated for each patient. Post-operative complications were recorded at final follow-up. Pearson correlations were determined for flexibility vs correction for all patients and were compared between etiologies and between device types (MCGR, TGR, VEPTR).


107 patients (14 congenital, 43 neuromuscular, 31 syndromic, 19 idiopathic) with mean age 7.1 years at index surgery were identified. Mean pre-operative scoliosis was 77°. Mean flexibility of 36% was not significantly different between etiologies. Mean immediate post-operative scoliosis was 46° (p < 0.001 vs. pre-operative) with mean correction of 38%. Correction rate was not significantly different between etiologies; however, correction rate was different between device types (MCGR 45%, TGR 40%, VEPTR 14%; p =  < 0.001). Pearson correlation for flexibility vs correction was fair (r = 0.37, p < 0.001). This correlation was observed for idiopathic (r = 0.53, p = 0.020) and neuromuscular (r = 0.46, p = 0.0020) scoliosis, but not for congenital or syndromic scoliosis. At a mean of 6.1 year follow-up (minimum 2 years to 15.5 years), 60 of 81patients (74%) experienced at least one complication. Odds ratio for developing a complication was 3.00 (1.03–8.76) for patients with pre-operative flexibility < 45% (p < 0.05).


As lower pre-operative flexibility was associated with less scoliosis correction and with a higher risk of post-operative complications, curve flexibility should be considered when deciding upon the timing of growth friendly surgery.

Level of evidence

Level III—retrospective comparative study.

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Availability of data

Registry data is available to member institutions. Measurements and analysis done at the IWK Health Centre are on a password protected server. Access may be arranged through application to the REB.

Code availability

Statistical analysis was conducted using Excel version 2002 (Microsoft Corporation, Redmond, Washington, USA) and R version 4.0.2. (R Core Team, Vienna, Austria).


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Authors and Affiliations




RB, KM, AM, BY, LA, PS, PS, GT, Pediatric Spine Study Group, RE-H: design or the acquisition, analysis, or interpretation of data, drafted the work or revised it critically, approved, accountable.

Corresponding author

Correspondence to Ron El-Hawary.

Ethics declarations

Conflict of interest

Riley Bowker has nothing to disclose. Kevin Morash has nothing to disclose. Amir Mishreky reports personal fees from Dalhousie University Faculty of Medicine Summer Student Research Program, during the conduct of the study. Burt Yaszay reports reports grants and personal fees from Stryker, grants and personal fees from Depuy Synthes, grants and personal fees from Nuvasive, personal fees from Biogen, personal fees from Medtronic, personal fees from Globus, personal fees from Orthopediatrics, outside the submitted work. Lindsay Andras reports personal fees from Zimmer Biomet, other from Eli Lilly, other from Journal of Pediatric Orthopaedics, personal fees from Medtronic, personal fees from Nuvasive, non-financial support from Orthobullets, other from Pediatric Orthopaedic Society of North America, other from Scoliosis Research Society, outside the submitted work. Peter Sturm reports personal fees from Nuvasive, personal fees from Depuy Synthes Spine, outside the submitted work. Paul Sponseller has nothing to disclose. George Thompson reports personal fees from Shriners Hospitals for Children, personal fees from OrthoPediatrics, personal fees from Wolters Kluwer, personal fees from Broadwater, other from Scoliosis Research Society, other from Nuvasive, outside the submitted work. Pediatric Spine Study Group reports grants from Pediatric Orthopaedic Society of North America, grants from Food and Drug Administration, grants from NuVasive, grants from DePuy Synthes Spine, grants from Children’s Spine Foundation, and grants from Growing Spine Foundation. Ron El-Hawary reports grants and personal fees from Depuy Synthes Spine, grants and personal fees from Medtronic Spine, personal fees and other from Orthopediatrics, other from Pediatric Spine Foundation, other from Scoliosis Research Society, personal fees from Wishbone Medical, personal fees from Globus Medical, outside the submitted work.

Ethical approval

This work is a sub-study of the Pediatric Spine Study Group Registry which was approved by the Research Ethics Board at the IWK Health Centre (#1002256) in accordance with the ethical standards outlined in the Tri-Council Policy Statement and the 1964 Declaration of Helsinki and its later amendments.

Consent to participate

All research participants or their legal guardians provided written consent to be a part of the registry and have the data collected be used in ongoing research on scoliosis.

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Not applicable.

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Bowker, R., Morash, K., Mishreky, A. et al. Scoliosis flexibility correlates with post-operative outcomes following growth friendly surgery. Spine Deform 10, 933–941 (2022).

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  • Early onset scoliosis
  • Growth friendly
  • MCGR
  • Flexibility