Study design: A retrospective study of a cohort of 132 girls with adolescent idiopathic scoliosis (AIS).
Objectives: Evaluate the changes in height and scoliosis angle over time by the use of a mathematical model and determine a relationship between height and angle values in patients with AIS.
Summary of background data: The influence of growth on idiopathic scoliosis (IS) is still not fully understood. Although it has not been completely demonstrated, it is accepted that a relationship exists between height growth and curve progression, as well as that curve stabilization occurs when growth ends, but it has not yet been demonstrated whether both occur at the same time.
Method: One hundred thirty-two girls were included in a retrospective study. Inclusion criteria were: adolescent IS, Cobb angle > or =10 degrees , menarche age well documented, and follow-up of at least 2 years in 6-month controls. Main variables were: menarche age, height, Cobb angle, and treatment. Height and angle changes over the time were adjusted by several curvilinear regression models. Calculations were made of the gradient between each consecutive time point (first derivative function). Growth was considered as tending to stabilize when the function gradient changed its sign or was negligible. Height and Cobb angle correlation coefficients for repeated measures were estimated within patients for curves managed with observation and curves managed with a brace. Comparisons among these correlations were based on the Fisher-Z transformation.
Results: Height function gradient changed sign at 1 year postmenarche, and Cobb angle function gradient was negligible around menarche. There was a correlation between mean heights and mean angles, being higher for girls managed only with observation. When comparing mean heights in one semester with the mean heights of the previous one, there were statistically significant differences until 2.5 years postmenarche, although after the first year, these differences were clinically irrelevant. A significant increase for angle values was observed in the same period for the group of girls managed with observation and in the 6 months before menarche for the girls managed with a brace.
Conclusions: A mathematical model was used to demonstrate when height and angle growths tend to stabilize (1 year after menarche for height values and at the time of menarche for angle values) in AIS. In the absence of a brace effect, a significant correlation between both growth rates was noted up until 2.5 years after menarche.