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Fig. 1 Patient wearing a Boston brace fitted with a temperature sensor.

AAOS Now

Published 7/1/2010
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Terry Stanton

Sensors show success of bracing for scoliosis

Bracing is effective for adolescent idiopathic scoliosis when compliance is good

Investigators who used sensors to monitor brace wear by patients with idiopathic adolescent scoliosis found that patients who wore their Boston brace consistently achieved better results than those who were less compliant. The study, “Brace Treatment Controls Progression in Adolescent Idiopathic Scoliosis,” conducted by Donald E. Katz, CO; J. Anthony Herring, MD; and colleagues, was named the outstanding clinical scientific paper at the 2010 annual meeting of the Pediatric Orthopaedic Society of North America.

The effectiveness of brace treatment for adolescent idiopathic scoliosis remains controversial and unproven, in large part due to the lack of accurate monitoring of wear. Estimates of wear by the patient, the parents, the treating physician, and the orthotist are unreliable, according to the authors. In the first year of bracing, for example, physicians fail to identify 25 percent of patients who were noncompliant with prescribed wear.

Grading on a curve
In the study, the investigators followed 100 of 126 patients whose curves were between 25 degrees and 45 degrees. The participants were prescribed Boston braces outfitted with heat sensors (Fig. 1) that measured the exact hours of brace wear. Patients were prescribed either 16 or 23 hours of brace wear, and the orthopaedic teams were blinded to the wear data. When treatment was completed, hours between brace wear were compared and the frequency of curve progression of 6 degrees or more and with progression to surgery.

Overall, the authors found a correlation between hours of brace wear and curve progression. The effect of brace wear duration was seen most markedly in patients with Risser scores of 0 or 1 at the beginning of treatment and in patients with open triradiate cartilage at the onset.

Patients who wore their braces to school and immediately afterward fared the best. In 82 percent of patients who wore braces more than 12 hours per day, curves did not progress, while lack of progression was seen in only 31 percent of those who wore the brace less than 7 hours (p = 0.0003). An inverse correlation was also seen between hours of wear and the need for surgical management (p = 0.0001).

The key to this study was the temperature data logger that was installed within each orthosis to achieve an accurate record of wear. Because the logger is not small enough to be concealed, patients were told that its purpose was to correlate temperature with the patient’s level of comfort, so as notto influence wear patterns. This approach was approved by the Institutional Review Board.

The temperature sensor is insulated from the environment and samples the temperature on the inside of the orthosis every 15 minutes. A previous trial had shown that the duration of wear as estimated by an algorithm was found to correspond to the actual logged wear duration with an accuracy of 99.93 percent.

When the patient puts on the brace, the sensor quickly equilibrates to within a few degrees of body temperature. The investigators recorded a wear time once the temperature stabilized to between 90ºF and 99ºF.

Tracking progress
The Boston braces were custom-fitted to the patients. After about 4 weeks of wear, patients returned for a standing posteroanterior (PA) radiograph while wearing the brace to document the amount of curve correction.

Subsequently, patients returned to the clinic every 4 months for a standing PA radiograph while not wearing the brace. Radiographic data included the curve type—single thoracic, thoracolumbar, lumbar, double major, double thoracic, and triple major; triradiate cartilage status (open or closed); and the Risser scale (Table 1).

In-brace correction was defined as the percentage of the improvement of the major curve on the standing brace-on radiograph compared with the most recent standing radiograph without the brace.

Successful completion of treatment was defined as a mature patient with less than 6 degrees of progression of the main curve out of the brace. For double curves, the curve with the largest Cobb measurement was termed the primary curve. Treatment failure was noted when the secondary curve progressed to a 6 degrees or more greater than the primary curve, or surgical management was required.

For the entire cohort, brace treatment was considered successful in 50 patients who had less than 6 degrees of progression of the major curve. Of the 75 pa-tients at the Risser 0 scale, 33 (44 percent) had nonprogression and 42 (56 percent) had progression. Success rates were higher in more mature patients, with two thirds of patients at Risser 1 maturity and 70 percent of patients at Risser 2 maturity. Curve type did not in-fluence outcome; treatment was successful in 33 of 63 patients (55 percent) with double major curves. Eleven of 26 patients with thoracic curves and 5 of 12 patients with other types of curves had successful outcomes (Table 2).

Lessons learned
The authors noted that “even our most compliant patients did not reach the prescribed level of wear over the entire bracing period, which averaged 18 months. When 23 hours were prescribed, the hours of wear were not sig-nificantly different than when 16 hours were recommended.” The authors said that patients most likely to have successful outcomes were those who wore the brace 12 or more hours per day, regardless of what was prescribed.

“We could speculate that brace wear while upright is biomechanically more important than brace wear while supine,” the authors wrote. “On the other hand, it is more likely that the successful outcomes in those wearing the brace beyond night time simply identifies the more diligent brace wearers.”

The study found no differences in hours of brace wear between boys and girls, although past studies have found that boys are frequently poor brace wearers. This finding, however, should be viewed with caution because the patient group included only 9 boys.

Disclosure information: Dr. Herring—Medtronic, Elsevier.

Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom line

  • A heat sensor fitted in a brace allowed investigators to record accurate daily brace wear times for patients with adolescent idiopathic scoliosis.
  • Bracing can be effective in preventing progression of curvature in these patients.
  • Bracing effectiveness depends on the length of time (hours per day) the patient wears the brace; a minimum of 12 hours per day of brace wear is required for efficacy.

Sensors show success of bracing for scoliosis