Predictability of in-brace correction and Cobb's Angle at Brace Weaning using supine radiographs for adolescent idiopathic scoliosis

Abstract

INTRODUCTION: For adolescent idiopathic scoliosis (AIS) patients undergoing brace, a 50% in-brace correction is the general rule. However, this is an arbitrary figure and does not take into account the curve flexibility. This study aimed to predict in-brace correction of scoliosis using our standard supine radiographs. METHODS: This is a retrospective correlation analysis of pre-brace supine and in-brace standing radiographs for patients undergoing Boston brace treatment for AIS. Patients with AIS undergoing brace treatment from June to December 2008 were reviewed from initial referral date until maturity. All included subjects were aged ≥10 years, Risser sign 0, premenarchal for girls and with a major curve of 25° to 40°. Supine radiographs were performed the day of brace fitting while the inbrace radiograph was taken after the patient had worn the brace for 2 weeks. Other analysed factors included age, gender, body height, weight, age of menarche, and self-reported brace compliance. The Cobb’s angle correction obtained by supine radiographs was used as prediction analysis of in-brace correction using linear regression. RESULTS: A total of 60 patients (55 females, 5 males) with a mean age of 11.9 years were recruited. The mean pre-bracing, supine and in-brace Cobb’s angles were 31.7°, 23.9° and 20.0°, respectively. Linear regression analysis showed strong positive correlation (R=0.713; p<0.001) between change in Cobb’s angle in supine and in-brace radiographs. CONCLUSION: This study showed that supine radiographs have predictive value for determining in-brace correction of AIS. Thus, curve flexibility has a strong effect on curve correction using bracing.