Curve magnitude and skeletal maturity are important factors in determining the efficacy of bracing for the treatment of adolescent idiopathic scoliosis (AIS), but curve morphology may also affect brace success, according to a study conducted to determine the influence of curve morphology on the response to bracing with a TLSO. The study concluded that patients with thoracic curves are at greater risk for brace failure than patients with lumbar curves, despite similar initial curve magnitudes and average amount of daily brace wear. A change in curve pattern may imply flexibility and is associated with brace success, according to the authors, and patients with thoracic curves should be counseled accordingly.
Researchers conducted a retrospective review of patients managed with an orthosis for the treatment of AIS. The patients were prospectively enrolled at the initiation of brace wear and were followed through completion of bracing or until surgery was performed. Inclusion criteria were main curves of 25-45 degrees and a Risser stage of 0, 1, or 2 at the time of brace prescription. Compliance with bracing was measured with Thermochron temperature data loggers. Radiographs made at brace initiation, brace cessation, and final follow-up were used to retrospectively categorize curves with use of the modified Lenke (mLenke) classification system and more broadly to categorize them as main thoracic or main lumbar. The effect of morphology on outcome was evaluated using chi-square and Fisher’s exact tests.
The study cohort included 168 patients. There was no difference in curve magnitude at the time of brace initiation or in average hours of daily brace wear between groups. The rate of surgery or progression of the curve to greater than or equal to 50 degrees was 34.5 percent (29 of 84) in mLenke-I curves, 54.5 percent (6 of 11) in mLenke-II curves, 29.4 percent (10 of 34) in mLenke-III curves, 17.6 percent (3 of 17) in mLenke-V curves, and 13.6 percent (3 of 22) in mLenke-VI curves. There were no mLenke-IV curves at the time of brace initiation. The rate of surgery or progression to greater than or equal to 50 degrees was 34.1 percent (44 of 129) in the combined thoracic group and 15.4 percent (6 of 39) in the combined lumbar group.
In brace-compliant patients (greater than 12.9 hours per day), the rate of surgery or progression to greater than or equal to 50 degrees was 30.3 percent (20 of 66) in main thoracic curves and 5.3 percent (1 of 19) in main lumbar curves. One-tenth of curves changed morphology during bracing. The rate of surgery or progression to greater than or equal to 50 degrees was 35.8 percent (43 of 120) in persistent main thoracic curves, 20 percent (6 of 30) in persistent main lumbar curves, 12.5 percent (1 of 8) in main thoracic curves that became main lumbar curves, and 0 percent (0 of 9) in main lumbar curves that became main thoracic curves.
The study was published June 7 in the Journal of Bone & Joint Surgery.