Improving prediction of progression of idiopathic scoliosis based on curve size and skeletal maturity.

Purpose: To define the risk of curve progression of idiopathic scoliosis (IS) to 35°, 40°, 45°, and 50° based on current curve magnitude and Sanders stage for boys and girls, using a large cohort of patients and encounters, to improve granularity and allow more accurate estimations to guide treatment.

Methods: Retrospective analysis of a prospectively collected scoliosis database. Generalized estimation equation logistic regression models estimated probabilities of curve progression to 35°, 40°, 45°, and 50° based on starting curve size and Sanders stage. Probabilities and their 95% confidence intervals were calculated for each combination of variables to each endpoint separately for boys and girls.

Results: A total of 309 patients (80% girls) were included. Starting curve size and Sanders stage were significant predictors for progression in both sexes (all P ≤ 0.04). Higher starting curve sizes and lower Sanders stages were associated with greater odds of progression. Risk of progression was still present even at higher Sanders stages.

Conclusion: IS curves follow a predictable pattern, having more risk for progression when curves are larger and Sanders stages are smaller. Risk of curve progression is a spectrum based on these factors, indicating some risk of progression exists even for many smaller curves with higher Sanders stages. The improved granularity of this analysis compared to prior efforts may be useful for counseling patients about the risks of curve progression to various curve size endpoints and may aid shared decision-making regarding treatments.

Level of evidence or clinical relevance: Level III: retrospective cohort study.