When Should We Wean Bracing for Adolescent Idiopathic Scoliosis?

Abstract

Background: Current brace weaning criteria for adolescents with idiopathic scoliosis (AIS) are not well defined. Risser Stage 4, ≥ 2 years since the onset of menarche, and no further increase in body height over 6 months are considered justifications for stopping bracing. However, despite adherence to such standards, curve progression still occurs in some patients, and so better criteria for brace discontinuation are needed.

Questions/purposes: (1) Is no change in height measurements over 6 months and Risser Stage 4 sufficient for initiating brace weaning? (2) What is the association between larger curves (45°) at brace weaning and the progression risk? (3) Are a more advanced Risser stage, Sanders stage, or distal radius and ulna classification associated with a decreased risk of curve progression? (4) When should we wean patients with AIS off bracing to reduce the time for brace wear while limiting the risk of postweaning curve progression?

Methods: All AIS patients who were weaned off their braces from June 2014 to March 2016 were prospectively recruited and followed up for at least 2 years after weaning. A total of 144 patients were recruited with mean followup of 36 ± 21 months. No patients were lost to followup. Patients were referred for brace weaning based on the following criteria: they were Risser Stage 4, did not grow in height in the past 6 months of followup, and were at least 2 years postmenarche. Skeletal maturity was assessed with Risser staging, Sanders staging, and the distal radius and ulna classification. Curve progression was determined as any > 5° increase in the Cobb angle between two measurements from any subsequent six monthly followup visits. All radiographic measurements were performed by spine surgeons independently as part of their routine consultations and without knowledge of this study. Statistical analyses included an intergroup comparison of patients with and without curve progression, binomial stepwise logistic regression analysis, odds ratios (ORs) with their 95% confidence intervals (CIs), and a risk-ratio calculation. A reasonable protective maturity stage would generate an OR < 1.

Results: Among patients braced until they had no change in height for 6 months, were 2 years postmenarche for girls, and Risser Stage 4, 29% experienced curve progression after brace weaning. Large curves (≥ 45°) were associated with greater curve progression (OR, 5.0; 95% CI, 1.7-14.8; p = 0.002) as an independent risk factor. Patients weaned at Sanders Stage 7 (OR, 4.7; 95% CI, 2.1-10.7; p < 0.001), radius Grade 9 (OR, 3.9; 95% CI, 1.75-8.51; p = 0.001), and ulna Grade 7 (OR, 3.1; 95% CI, 1.27-7.38; p = 0.013) were more likely to experience curve progression. The earliest maturity indices with a reasonable protective association were Sanders Stage 8 (OR, 0.21; 95% CI, 0.09-0.48; p < 0.001), and radius Grade 10 (OR, 0.42; 95% CI, 0.19-0.97; p = 0.042) with ulna Grade 9 (no patients with curve progression).

Conclusion: Brace weaning indications using Risser staging are inadequate. Curve progression is expected in patients with large curves, irrespective of maturity status. Bone age measurement by either Sanders staging or the distal radius and ulna classification provides clearer guidelines for brace weaning, resulting in the least postweaning curve progression. Weaning in patients with Sanders Stage 8 and radius Grade 10/ulna Grade 9 provides the earliest and most protective timepoints for initiating brace weaning.

Level of evidence: Level II, prognostic study.

Fig. 1

This radiograph demonstrates the appearance of Risser Stage 4, which is identified as ossification of the whole length of the iliac apophysis that is not yet fused to the ilium.

Fig. 2

This radiograph shows Sanders Stage 7 with closure of all digital physes except for the distal radius and ulna. On this same radiograph, the distal radius and ulna classification is considered radius Grade 9 (narrowing of the whole physeal plate without fusion) and ulna Grade 8 (fusion of > 50% of the medial ulna physis).

Fig. 3

On this hand and wrist radiograph, the Sanders stage is still 7 because the distal radius physis is white; however, for the distal radius and ulna classification, the radius grade is 10 (fused physis but scar still seen) while the ulna grade is 9 (complete fusion of the physeal plate).

Fig. 4

We mapped the curve progression rate for Risser staging, Sanders staging and the distal radius and ulna classification. The arrows indicate the direction in decreasing curve progression rate with advancements in skeletal maturity. The curve progression rate was 0% in those with radius Grade 10/ulna Grade 7 and ulna Grade 9, Radius Grade 10/ulna Grade 8 in those with Risser Stage 5, and at radius Grade 11.