Brace Wear Control of Curve Progression in Adolescent Idiopathic Scoliosis

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J.A. Herring, D.E. Katz, R.H. Browne, D.M. Kelly, and J.G. Birch reply:
We welcome this opportunity to reply to Dr. Price’s observations about our study relating brace wear to control of progression of adolescent idiopathic scoliosis. He notes, and we fully agree, that a simple correlation does not prove a conclusion, and, we would add, does not prove cause and effect.
We began this study with true uncertainty regarding the effectiveness of bracing and only concluded that bracing altered progression when we discovered quite complex positive correlations between treatment and outcome. Many studies have supported the finding that curves progress most during the adolescent growth spurt and that closure of the triradiate cartilage is a valid indicator of a decline in the growth velocity curve. If bracing were ineffective, the least evident correlation should be in the patients entering treatment with an open triradiate cartilage. We found, to the contrary, that these rapidly growing adolescents had the strongest correlation between curve control and hours of brace wear. We then dissected out the time of brace wear compared with lack of curve progression and found that night wear, which most patients find the most tolerable, had the least correlation with successful treatment. In the group with an open triradiate cartilage, the greatest effective wear occurred when the patient wore the brace while upright, with wear to school and after school being the most important. We also looked at those with closed triradiate cartilage at the time of presentation and found a clear dose-response curve with a different slope, representing the less progressive nature of scoliosis at this growth stage. The graphs for time of wear likewise had a different slope but demonstrated the same relationship, with day wear being more important than night wear. In other words, we found consistent relationships between hours of wear and scoliosis control through multiple analyses with different variables.
Dr. Price suggests that a patient with a nonprogressive curve will wear the brace because it is more comfortable. We recorded patient-reported comfort at each visit and found no correlation between comfort and brace wear. We analyzed curve flexibility with the same hypothesis but did not find greater wear in those with more flexible curves, which theoretically may make the brace more comfortable. Dr. Price also suggests that patients who were labeled as noncompliant would further reduce their brace wear. In this study, the only patients who were considered noncompliant were the small number of patients who gave back the braces. In addition, the treating team and the patients were blinded to wear data throughout treatment. The previously published study of these patients1 demonstrated that the patient’s report of wear and the orthotist’s and doctor’s estimations of wear did not correlate with actual wear. Dr. Price notes that bracing is not benign, and we agree completely. The successful patients in our study wore the brace for more than twelve hours per day for an average of eighteen months. We in no way imply that bracing is easy, just that it is effective. At least now when we encourage a patient to wear the brace, we have evidence that it is worth the effort, and we have some concept of the required daily hours of wear.
As noted in The Journal’s online review by Aronsson and Stokes2, Level-II studies such as this one are of great importance in surgical fields and provide information that is not otherwise obtainable because of the difficulties of patient accrual for Level-I studies.
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