The efficacy of bracing for adolescent idiopathic scoliosis remains controversial, despite the fact that braces have been routinely prescribed since the 1950s. Whether braces affect the natural history of adolescent idiopathic scoliosis has been debated for too long, and it is still considered ethically permissible to study brace efficacy by randomizing the treatment recommended to patients. This paper examines a key issue: how much brace wear is effective? "If you don't follow your doctor's instructions, the treatment may not work" is one take-home message of this paper. Actually, the converse is where the real significance lies; braces evidently can be effective, provided that they are worn for sufficient time.
Since brace treatment is not considered to be effective for adults, the debate centers on children with adolescent idiopathic scoliosis. But where exactly do the limits of efficacy lie? This line of thought leads to two important questions: First, does the brace effectively prevent progression of the curve in young patients; and second, at what curve magnitude and at what skeletal age are the advantages of brace treatment outweighed by the disadvantages?
This prospective study provides some insight into the first question of efficacy and provides strong evidence that there is a dose-response relationship between brace efficacy and the total amount of time that the brace is worn. The authors conclude that the Boston brace (Boston Brace International, Avon, Massachusetts) can decrease the frequency of Cobb-angle progression and operative intervention. This finding is not entirely unexpected, and it helps to resolve conflicting reports from prior investigations of efficacy. In 1987, Houghton et al.1 presented objective data showing that compliance with recommended brace wear was a problem among adolescents. The present study also builds on the finding in the study by Rahman et al.2 that thirty-four patients had better outcomes if they wore their braces for longer periods of time.
The second question, which is not formally addressed by Katz et al., is at what age and at what curve magnitude do the disadvantages of bracing outweigh the advantages? If the mode of action of a brace requires that there be some residual growth sensitive to mechanical loading3, then early intervention is indicated. Sanders et al.4 reported on a simplified method of classification to predict progression of adolescent idiopathic scoliosis on the basis of the skeletal age of the patients. They reported eight stages of skeletal maturity that were based on capping and closing of the finger and distal radial physes as seen on an anteroposterior radiograph of the hand. They correlated skeletal maturity with the risk of progression of adolescent idiopathic scoliosis and found that scoliosis curves mainly progress between Stage 2 and Stage 5. Stage 2 is the beginning of puberty; Stage 3 correlates with peak growth velocity; Stage 4 correlates with Risser 0 and an open triradiate cartilage; Stage 5 correlates with Risser 0, a closed triradiate cartilage, and premenarcheal adolescents; and Stage 6 correlates with Risser 1, a closed triradiate cartilage, and postmenarcheal adolescents. The authors concluded that, by Stage 5, the risk of a curve further progressing to require surgical correction is minimal.
In the present study, ninety-one of the 100 patients were girls and fifty-five (60%) had already reached menarche before treatment was started. Fifty-three had closed triradiate cartilages, and, in five patients, the status of the triradiate cartilage was unknown. If these five patients also had a closed triradiate cartilage, 58% of the patients in this study would have been classified as having Stage-5 skeletal maturity by the system of Sanders et al.4, which would place them at a very low risk of progression. Despite this shortcoming, the authors of the present study showed a close correlation between hours of brace wear and a successful outcome, defined as curve progression of <6°. Successful treatment was found in 82% of patients who wore the brace for more than twelve hours per day, 61% in patients who wore the brace between seven and twelve hours per day, and 31% in patients who wore the brace for fewer than seven hours per day. It is important to note that the skeletal maturity of the patients had a major effect on the results of the present study. A successful outcome (defined as progression of <6°) occurred in 44% of the patients who were Risser 0, in 67% of those who were Risser 1, and in 70% of those who were Risser 2. Similarly, a successful outcome occurred in 29% of the patients who had an open triradiate cartilage and in 66% of the patients who had a closed triradiate cartilage.
The study design is innovative and efficient (no external funding was required to conduct it), yet it only represents Level-2 evidence, since it is not a randomized trial. Rather than detracting from the quality of the work, this designation draws attention to a weakness in the assignment of level of evidence. That designation may work well in trials of pharmaceutical agents compared with placebos, but, in orthopaedics, a more creative approach to study design is usually required, as is evident in this paper.
There are some methodological aspects of note. While substantial attention is given to accurate measurement of brace wear, the Cobb angle, which is the dependent variable, remains a potential Achilles heel of the study. The Cobb angle must be measured with great care from a given radiograph to achieve the study's threshold precision, indicating a 6° change. The patient's spinal shape in any one radiograph depends on several factors, including posture, time of day5, and patient positioning for the radiograph. Because the spine is flexible, the Cobb angle is a "moving target" that does not distinguish between the vertebral and disc components of the scoliosis deformity.
Some points made within the discussion merit additional attention. If brace wear is not to be full time, then the daytime and evening hours appear to be the most effective times. This casts some doubt on night-time bracing, although some night-time only braces are designed differently than the Boston brace to overcorrect when worn and such overcorrection is not practical during the waking hours. The effect of stage of maturation at the onset of treatment is potentially confusing, since patients who were prescribed a brace at a later stage of maturity had a better outcome. This finding was probably due to the more mature patients having already passed their peak growth velocity, which would mean that the rapid progression of the scoliosis during puberty was slowing down. It seems to be clear that early intervention, contingent on early detection, is a key factor in the success of brace treatment for patients with adolescent idiopathic scoliosis.
In conclusion, this manuscript adds important information to the literature concerning the efficacy of bracing in the treatment of adolescent idiopathic scoliosis. This study reports the largest series to date of patients treated with a brace that accurately reported the number of hours that it was worn. The results support the concept that if a brace is worn as prescribed, the success of preventing curve progression in patients with adolescent idiopathic scoliosis is high. In fact, the authors were able to generate a dose-response curve in which the number of hours the brace was worn was correlated with the success rate in preventing curve progression. However, many patients did not avoid the need for surgery, and the reasons for this may require more intense study of younger, less skeletally mature patients as well as those known to be at greatest risk of progression in the absence of any treatment.
*In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the National Institutes of Health. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.
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