Curve progression matching with skeletal growth in adolescent idiopathic scoliosis using the distal radius and ulna (DRU) classification

Abstract

Introduction: For adolescent idiopathic scoliosis (AIS) patients, it is important to determine their peak growth velocity for timely treatment in preventing curve progression. The ability to predict when the curve progression risk is greatest is necessary to maximize benefits of any intervention. Currently, there was limited information regarding the period of bracing and timing of weaning with success of curve control, particularly in relation to growth. This study aims to determine if there is any relationship between skeletal growth rate and curve progression rate in AIS patients, and how the distal radius and ulna (DRU) classification is able to define these parameters. Material and Methods: Data collection was performed for the growth parameters and Cobb angle of AIS patients who presented at Risser 0-3 and followed to maturity at Risser 5. Standing body height (BH), arm span (AS), curve magnitude, Risser sign and the DRU classification were studied. For analysis of clean data free from the effects of interventions such as bracing or surgery, only data from initial presentation to commencement of intervention was recorded. Growth rate (based on BH and AS) and the curve progression rate were then calculated for each DRU grade. Statistical analyses included Spearman correlation coefficient and paired t-test. Results: A total of 318 AIS (74.2% females) patients with mean age of 12.3 ± 1.5 years were studied. Mean follow-up before commencing intervention/reaching skeletal maturity was 4.3 ± 2.3 years. Significant correlations were found between radius and ulna grades with both the growth and curve progression rates (p < 0.001), the curve progression rate also significantly but weakly correlated (p < 0.001) with growth rates. When comparing peak growth and peak curve progression, there were statistical significant difference (p < 0.001) for both radius and ulna grades at which these peaks occurred. The curve progression peaked consistently after peak growth by a significant difference of one radius and ulna grade. The peak rate of curve progression can occur up to 8.3 months after the peak growth spurt of both body height (BH) and arm span (AS). Reductions in growth and curve progression rates reached a plateau at R9 and U7 (DRU grades). Conclusion: By utilizing the DRU grading, this large-scale study illustrates that the maximal curve progression occurs after the peak growth spurt, suggesting that the curve should be monitored closely even after peak growth. Our findings also demonstrate the period of potential curve continuing progression beyond the peak curve progression phase until the end of impactful growth. It is crucial that that DRU grades are capable to define such close relationship between growth and curve progression. The clinical use of DRU allows observation of not only growth at the important period before skeletal maturity, but how that relates to scoliotic curve progression rate as well. This plays a role in clinical decision-making on the timing of any scoliosis interventions.