Predicting curve progression at skeletal maturity in adolescent idiopathic scoliosis using the distal radius and ulna classification

Abstract

Purpose: The aim of study is to determine the risk of clinically significant curve progression in adolescent idiopathic scoliosis (AIS) based on the initial Cobb angle and test the utility of the distal radius and ulna (DRU) classification in predicting these outcomes. Methods: This was a prospective study of all AIS patients who presented with Risser sign of 0-3 and were followed till skeletal maturity or surgery, with minimum 2-year follow-up. Outcomes of 40° and 50° were used for analysis based on the cut-offs of adulthood progression risk and surgical threshold, respectively. Statistical analyses were performed with logistic regression to determine probabilities of reaching curve progression of 40° or 50° based on initial Cobb angle and DRU grading. Results: A total of 513 AIS patients was studied. At R6/U5, most curves (probability ≥48.1-55.5%) beyond Cobb angle of 25° progressed to the 40-degree threshold. For curves 35° or more, there was high risk of unfavorable outcomes regardless of maturity. Most patients at R9 did not progress regardless of initial curve magnitude (probability 0% to reach 50-degree threshold for initial Cobb angle ≥35 degrees). Conclusion: This large-scale study illustrates the utility of the DRU for predicting curve progression and may guide timing of treatment. AIS patients who are skeletally immature at high risk for progression to 40° or 50° at the end of growth despite a mild initial curve. Those with a scoliosis ≥35° are at increased risk of an unfavorable outcome despite being near skeletal maturity.