Novel supine correction index helps predict brace outcomes in adolescent idiopathic scoliosis patients

Jason Cheung

Curve progression with brace treatment in patients with adolescent idiopathic scoliosis (AIS) can be predicted by their curve flexibility and in-brace correction rate, new research shows. The findings—which were published in The Bone and Joint Journal by Jason Cheung (University of Hong Kong, Hong Kong) et al—indicated that a higher supine flexibility and correction rate, as well as a supine correction index (SCI) of greater than 1.21 predicted a lower risk of curve progression in bracing in patients with AIS.

The study aimed to assess the ability of morphological spinal parameters to predict the outcome of bracing in patients with AIS and to establish a novel SCI for guiding bracing treatment.

Patients with AIS to be treated by bracing were prospectively recruited between December 2016 and 2018, and were followed until brace removal. A total of 207 patients with a mean age at recruitment of 12.8 years (standard deviation [SD]: 1.2) were enrolled in the study.

Cobb angles, supine flexibility, and the rate of in-brace correction were measured and used to predict curve progression at the end of follow-up. The SCI was defined as the ratio between correction rate and flexibility. Receiver operating characteristic (ROC) curve analysis was carried out to assess the optimal thresholds for flexibility, correction rate, and SCI in predicting a higher risk of progression, defined by a change in Cobb angle of ≥5° or the need for surgery.

The study found that baseline Cobb angles were similar (p=0.374) in patients whose curves progressed (32.7° [SD 10.7]) and in those whose curves remained stable (31.4° [SD 6.1]). In addition, high supine flexibility (odds ratio [OR] 0.947; 95% confidence interval [CI], 0.910 to 0.984; p=0.006) and correction rate (OR 0.926; 95% CI, 0.890 to 0.964; p<0.001) predicted a lower incidence of progression after adjusting for Cobb angle, Risser sign, curve type, menarche status, distal radius and ulna grading, and brace compliance.

ROC curve analysis identified a cut-off of 18.1% for flexibility (sensitivity 0.682, specificity 0.704) and a cut-off of 28.8% for correction rate (sensitivity 0.773, specificity 0.691) in predicting a lower risk of curve progression. A SCI of greater than 1.21 predicted a lower risk of progression (OR 0.4; 95% CI, 0.251 to 0.955; sensitivity 0.583, specificity 0.591; p=0.036).

Speaking to Spinal News International, Cheung said: “Joint decision-making between parents and clinician is necessary when prescribing brace treatment for adolescent idiopathic scoliosis. Success often requires substantial discussion and proper explanation of the expected treatment process. By providing prognostic data, the ability of the child to tolerate prolonged treatment and of the parents to encourage their child to comply with brace-wear time is greatly enhanced.

“In this study, we identified curve flexibility (via supine radiographs) and brace fitting (in-brace correction rate) as two major prognostic factors for brace success. In particular, the supine correction index, calculated based on supine curve flexibility and in-brace correction rate, of greater than 1.21 predicts a lower risk of curve progression. This is a useful tool for the clinician to gauge the likelihood of brace success and for effective counselling of patients and their parents.”


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