Brace Success as Related to Curve Type, Compliance, and Maturity in Adolescents with Idiopathic Scoliosis

Commentary The Bracing in Adolescent Idiopathic Scoliosis Trial (BrAIST) definitively demonstrated that patients who wear a thoracolumbosacral orthosis (TLSO) have a significantly greater chance of preventing the spinal curvature from reaching the commonly accepted surgical threshold of ≥50° during adolescence as compared with patients not managed with bracing1. While these general results were important for refuting the skepticism surrounding bracing, many questions persist related to brace use. This latest study by Dr. Thompson and coauthors addresses an important question: Is the effectiveness of the TLSO dependent on the curve type? The authors address this question by retrospectively comparing the responses of thoracic-dominant (main thoracic) and lumbar-dominant (main lumbar) scoliosis to bracing using Boston or computer-aided design (CAD), solid underarm TLSOs. The investigators used a modification of the Lenke classification (mLenke) to categorize curves. In this modification, a minor curve is considered “structural” if its magnitude is ≥80% of the dominant (major) curve. The authors provided a sound rationale for defining “structural” and the curve types within the mLenke classification scheme. Their approach has merit for assessing smaller scoliosis curves over time, when bending radiographs are less relevant. Nonetheless, we need a longitudinal study to test the stability of the mLenke classification as defined by the authors. The study provides convincing evidence that bracing with a TLSO is more effective for lumbar-dominant curves than for thoracic-dominant curves. The rate of reaching the surgical threshold was 15.4% for lumbar-dominant patterns compared with 34.1% for thoracic-dominant patterns. Compliance, defined as wearing the brace >12.9 hours/day, did enhance the treatment effect for both patterns, reducing the rate of those reaching the surgical threshold to approximately 30% for thoracic-dominant curves and approximately 5% for lumbar-dominant curves. Therefore, considering that the failure rate in the BrAIST observation group was 58%, one can see that bracing is effective in treating both thoracic-dominant and lumbar-dominant scoliosis. An exception may be curves with the mLenke-II pattern, in which a 54.5% rate of reaching the surgical threshold was found. At least 10 of the original 222 patients were excluded from the trial for losing or failing to wear the brace and only 85 (51%) of 168 patients in the cohort wore the brace the requisite time of >12.9 hours/day, underscoring the demanding nature of brace treatment for adolescent boys and girls. However, the study reinforces the body of literature showing that compliance is important for success. Maxim Integrated Thermochron i-Buttons or similar devices can be used to monitor the patients’ time in the brace and to counsel the patients and their parents. These devices are commercially available, and practitioners managing these patients should consider adopting such devices. Scoliosis is not a static condition, and the follow-up of patients after brace completion and beyond Risser stage 4 revealed that approximately 33% of the curves had progressed >5° and 22% had progressed to ≥50° at the last assessment (a mean of 22 months after brace cessation). The progression rate was similar for both thoracic-dominant and lumbar-dominant curves. These longer-term results must be evaluated with caution, since 18% of the cohort was lost to follow-up after reaching the end points for bracing. Several obvious questions on the use of the TLSO for treatment of adolescent idiopathic scoliosis remain. Can success be predicted by flexibility or “in-brace correction”? This study suggests that flexibility is important, as the patients with a thoracic-dominant curve who demonstrated a conversion to a lumbar-dominant curve had a greater success rate with bracing. The study’s main finding evokes the question, is there a better approach for treating thoracic-dominant curves? Some practitioners now have patients use a nighttime bending brace in conjunction with the standard TLSO2. Is this reasonable? What should we do with the mLenke-II double thoracic curves? Consideration of the effect of thoracic lordosis on brace success has yet to be studied, to my knowledge. The low rate of scoliosis in males prevents generalization of results across sex. Similarly, obesity is likely to reduce effectiveness. Further, as in many other clinical studies, the sample size was inadequate to account for maturity and growth as drivers of scoliosis progression. Of the 49 patients entering the study at Risser stage 1 or 2, only 2 developed curves (both thoracic) of ≥50°. Thus, there is a need for larger-scale studies to determine the impact of these important variables3. In 2005, the Scoliosis Research Society (SRS) published guidelines4 to help standardize inclusion criteria based on defining the population at risk for progression as well as outcome measures relevant to the natural history of adolescent idiopathic scoliosis. Some may disagree with the accepted end points (Risser stage 4 and a curve of ≥50°), but the benefits of consistent application can now be appreciated. Many important published studies3,5 have adopted the guidelines. Because of the consistent research approach, we can now say definitively that the TLSO is effective if the patient is compliant. An important message from this study is that thoracic scoliosis, especially in the immature patient (Risser stage 0), is less responsive to treatment with a TLSO, even if the patient is compliant. The next step for the SRS is to organize a multicenter study that focuses specifically on this highest-risk group.