Decreased Bracing Effectiveness in Overweight Patients with Adolescent Idiopathic Scoliosis

Purpose: To determine whether overweight patients with adolescent idiopathic scoliosis (AIS) are less successful with bracing than those who are not overweight.

Methods: We reviewed all AIS cases at our institutions for the past ten years who met the inclusion criteria: no prior treatment, Custom TLSO or Boston brace use, curves 25-40 degrees with Risser sign 0-2 at brace initiation, and follow-up to skeletal maturity. Overweight was defined as a body mass index >85th percentile. Success with bracing was defined as curve progression <5 degrees. Statistical analysis included independent t-test, multiple regression analysis, and calculation of the odds ratio.

Results: There were 276 patients who met the inclusion criteria and had sufficient data for analysis, with 12% (34) overweight. Average age at bracing was 12.8 years. The mean time in the brace was 14.3 hours per day (S.D. 5.5) and the mean initial curve magnitude was 32.5 degrees (S.D. 4.35). Curve progression ranged from -20 to 47 degrees with a mean progression of 4 degrees and a standard deviation of 9 degrees for the whole sample. For those overweight versus not overweight the curve progressions means were 8.8 degrees (S.D. = 7.9) and 3.6 degrees (S.D. = 9.3), respectively. The range of curve progression was -10 to 25 degrees for those who were overweight and -20 to 47 degrees for those not overweight. There is a statistically significant difference between the mean curve progression of the overweight patients versus those not overweight (t = -3.108, df -=274, p <.01). Regression analysis showed that 14.6% of the variance in curve progression is explained by average hours in brace per day, being overweight, gender, and age when brace started (F= 11.554, p < .001). Those patients who were overweight were 2.5 times as likely to be unsuccessful than those who were not overweight.

Conclusion: The results suggest that overweight AIS patients will have greater curve progression and be less successful with bracing than those not overweight. The ability of a brace to transmit corrective forces to the spine through the ribs and soft tissue may be compromised in overweight patients.

Significance: The effect of being overweight on the outcome of bracing children with AIS has not been reported. This factor should be taken into account when making treatment decisions. Further study is warranted to determine a threshold effect.