A Predictive Model of Progression for Adolescent Idiopathic Scoliosis Based on 3D Spine Parameters at First Visit

Marie-Lyne Nault, MD, PhD; Marie Beauséjour, PhD; Marjolaine Roy-Beaudry, MSc; Jean-Marc Mac-Thiong, MD, PhD; Jacques de Guise, PhD; Hubert Labelle, MD; Stefan Parent, MD, PhD


Spine. 2020;45(9):605-611. 

In This Article

Abstract and Introduction


Study Design: Prospective cohort study.

Objective: The objective of the present study was to design a model of AIS progression to predict Cobb angle at full skeletal maturity, based on curve type, skeletal maturation, and 3D spine parameters available at first visit.

Summary of Background Data: Adolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) spinal deformity that affects 1% of adolescents. Curve severity is assessed using the Cobb angle. Prediction of scoliosis progression remains challenging for the treating physician and is currently based on curve type, severity, and maturity. The objective of this study was to develop a predictive model of final Cobb angle, based on 3D spine parameters at first visit, to optimize treatment.

Methods: A prospective cohort of AIS patients at first orthopedic visit was enrolled between 2006 and 2010, all with 3D reconstructions. Measurements of five types of descriptors were obtained: angle of plane of maximum curvature, Cobb angles, 3D wedging, rotation, and torsion. A general linear model analysis with backward selection was done with final Cobb angle (either just before surgery or at skeletal maturity) as outcome and 3D spine parameters and clinical parameters as predictors.

Results: Of 195 participants, 172 (88%) were analyzed; average age at presentation was 12.5 ± 1.3 years and mean follow-up to outcome, 3.2 years. The final model includes significant predictors: initial skeletal maturation, curve type, frontal Cobb angle, angle of plane of maximal curvature, and 3D disk wedging (T3-T4, T8-T9) and achieved a determination coefficient (R2) = 0.643. Positive and negative predictive values to identify a curve of 35 degrees are 79% and 94%.

Conclusion: This study developed a predictive model of spinal curve progression in scoliosis based on first-visit information. The model will help the treating physician to initiate appropriate treatment at first visit.

Level of Evidence: 3


Adolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) spinal deformity affecting mostly girls. It begins at the time of the pubertal growth spurt and the cause is often unclear. The prevalence of AIS with a Cobb angle of 10° or more is 1.34% (95% CI = [0.98%–1.70%]) in children between 10 and 17 years old.[1,2] A major clinical challenge is the difficulty of predicting curve progression at the initial presentation in the individual patient.

Historically, curve magnitude, skeletal maturation, and chronological age were considered relevant risk factors of curve progression.[3] Curve location was suggested as an additional factor and patient maturity was better described relying on skeletal age from the Risser sign and the Tanner–Whitehouse score, as well as menarcheal status.[2–4] The Risser sign is the state of ossification and fusion of the iliac apophysis (stages 0–5), corresponding to skeletal maturation. These risk factors are not sufficiently discriminant to adequately support treatment decision and they cannot accurately predict final deformity. A nomogram has been developed to assess the incidence of progression for specific curves,[3] but its use is suggested only as a reference for counselling families about the risk of progression, rather than for guiding treatment. A review[4] confirmed that there were no objective measures to reliably predict curve progression in order to choose appropriate candidates for early curve management. Uncertainty regarding curve progression and outcome can create anxiety in families and patients with scoliosis as well as unnecessary psychosocial stress associated with brace treatment. The failure to accurately predict the risk of progression can also lead to nonoptimal treatment, either by precluding timely, appropriate and efficient management, or by generating unnecessary medical visits and radiographs.

Previous data suggest that the 3D morphology of the spine can help predict AIS progression. Recent prospective and retrospective studies showed that nonprogressive and progressive groups differed in various 3D morphological parameters at the very first visit to the orthopedist.[5,6]

A recent report by the 3D Scoliosis Committee of the Scoliosis Research Society (SRS) reinforced the importance of a clinically useful 3D classification to characterize spinal deformity and optimize surgical correction in severe cases.[7] However, the potential of 3D spinal parameters to predict curve progression in mild and moderate scoliosis has not been determined.

The objective of the present study was to design a model of AIS progression to predict Cobb angle at full skeletal maturity, based on curve type, skeletal maturation, and 3D spine parameters available at first visit. This study specifically targeted patients with mild to moderate AIS and the potential for significant further growth, in whom the risk of progression remained unknown and was highly important for guiding treatment.