Factors That Influence In-Brace Correction in Patients with Adolescent Idiopathic Scoliosis

Objective

To identify the factors affecting in-brace correction in patients with adolescent idiopathic scoliosis (AIS).

Methods

We performed a retrospective analysis of patients with AIS receiving Gensingen brace treatment in our scoliosis center from July 2015 to October 2017 was performed. The selection of patients was in accordance with the Scoliosis Research Society inclusion criteria for a bracing study. Some radiographic and clinical parameters, including the Cobb angle, rib–vertebra angle difference, coronal and sagittal balance, lumbar–pelvic relationship (LPR), Risser sign, curve type, age, gender, height, weight, body mass index, and menstrual status were collected. The correlation and difference analyses were performed to identify the factors influencing in-brace correction.

Results

A cohort of 112 patients with AIS (94 girls and 18 boys) were included in the present study. The mean in-brace correction was 59.29% ± 22.33% (range, 16.22%–100.00%). In-brace correction showed a significantly negative correlation with the major curve Cobb angle, minor curve Cobb angle, total curve Cobb angle, and LPR (P < 0.05 for all). Sagittal and coronal imbalance could reduce the curve correction (P < 0.001 and P = 0.008, respectively). The remaining parameters were not related to in-brace correction.

Conclusions

In-brace correction in the present study was 59.29% ± 22.33% (range, 16.22%–100.00%). Some factors, including the Cobb angle, sagittal and coronal balance, and LPR, have an effect on in-brace correction. The results from the present study can provide some useful information for brace design and fabrication.

Introduction

Adolescent idiopathic scoliosis (AIS) is a complex 3-dimensional deformity of the spine with a lateral curvature >10° that affects ∼2%–3% of adolescents.¹ A brace has been used for the management of skeletally immature patients with mild AIS for nearly 45 years. The effectiveness of the brace has been controversial for many years owing to the shortage of level 1 data.2, 3, 4, 5, 6 To solve the controversy, the Scoliosis Research Society has proposed the standardization of criteria for future AIS brace studies.⁷ The Bracing in Adolescent Idiopathic Scoliosis Trial by Weinstein et al.⁸ has confirmed the efficacy of brace treatment. In their study, the brace group had a greater success rate compared with the observation group (72% vs. 48%). Thus, bracing has become the reference standard for the conservative treatment of AIS.

Despite the high rate of bracing success, some patients will still experience bracing failure. Previous studies have found that in-brace correction, compliance, curve type, Risser sign, body mass index, and gender can contribute to the failure of brace treatment.9, 10, 11, 12, 13, 14, 15 Of these factors, in-brace correction might be the most important predictive factor for curve progression in braced patients with AIS.5, 6, 9 In-brace correction refers to the percentage of decrease in the curve size at the initial brace prescription. However, unlike most established surgical criteria, no definite in-brace correction has been determined that can expect to result in positive outcomes from brace treatment. Previous investigators have reported several cutoff points for in-brace correction to stratify patients with different bracing outcomes, including 10%, 30%, 40%, 50%, and 60%.4, 9, 16, 17, 18 An in-brace correction of 50% has been widely recognized as the aim of brace treatment in clinical practice.3, 5 Given the significance of in-brace correction, some studies have been performed to determine the best method to predict the in-brace correction. Ohrt-Nissen et al.¹⁹ reported that supine lateral bending radiographs could closely estimate the expected in-brace correction. Cheung et al.²⁰ found a significant correlation between the supine Cobb angle and in-brace Cobb angle. In the study by Weiss et al.,²¹ in-brace correction was found to negatively correlate with the Risser sign, patient age, and primary curve Cobb angle. However, the potential risk factors for in-brace correction have not been well elucidated. The purpose of the present study was to identify the factors influencing in-brace correction in patients with AIS.