The effect of thoraco-lumbo-sacral orthosis wear time and clinical risk factors on curve progression for individuals with adolescent idiopathic scoliosis.

Background Context: The effectiveness of bracing with a thoraco-lumbo-sacral orthosis (TLSO) for adolescent idiopathic scoliosis (AIS) has been studied extensively, with a growing body of evidence supporting TLSO use. In this study we examine the effect of wear time and other important causal factors affecting curve progression and develop a risk model that can be applied to individual patients and is based on important casual factors.

Purpose: Understand the impact of TLSO wear time and other risk factors in order to guide optimal treatment.

Study Design/setting: Prospective, multicenter, cohort study.

Patient Sample: Individuals with a diagnosis of AIS, age of 10 to 16 years, primary Cobb angle of 20° to 45°, Risser 0 to 2, <1 year post menarche if female, who were to be treated with a TLSO.

Outcome Measures: (1) Rate of primary curve progression, (2) surgery recommendation during TLSO treatment.

Methods: Wear time was monitored with thermochrons. Participants were followed until the end of growth. We examined the causal effects of wear time and baseline skeletal maturity as measured by triradiate cartilage (TRC) status, Cobb angle, and age. We then fit an outcome prediction model (logistic regression) based on important casual factors.

Results: Our final cohort consisted of 145 individuals (baseline age 12.1-13.4 years). Wear time was an important cause of response to treatment, including an interaction with TRC status. Baseline Cobb angle and age were also meaningful causes of response. The prediction model was accurate (79%) and had good specificity (81%) and moderate sensitivity (68%) and an area under the receiver operating characteristic curve (AUC) of 0.81. Additionally, we were able to independently confirm previous estimates of treatment efficacy, with an odds ratio around 2.0.

Conclusions: Our study showed the explicit causal effects of wear time, and baseline skeletal maturity, Cobb angle and age. The risk model we developed can be used for counseling patients and their families regarding TLSO wear and expectations for outcome.