Do Children With Blount Disease Have Lower Body Mass Index After Lower Limb Realignment?

Background: Children with Blount disease are typically obese. The goal of our study was to assess whether children with Blount disease had lower body mass index (BMI) after surgical correction of their lower limb deformity. Methods: A surgical data base was used to identify children with Blount disease. Demographic information including age of disease onset, ethnicity, health insurance status, and laterality was noted. Preoperative and most recent BMI values were documented. Using full-length standing radiographs, the mechanical axis deviation (MAD) and leg length discrepancy (LLD) were measured preoperatively and at latest follow-up. The relationship of the change in BMI with various demographic and radiologic parameters was evaluated. Results: Fifty-one children (32 males, 19 females) with Blount disease (23 early onset, 28 late onset) affecting 70 lower extremities (32 unilateral and 19 bilateral) underwent a variety of surgical procedures. All 47 children who underwent gradual correction with external fixation also underwent nutritional counseling while receiving inpatient rehabilitation. At an average follow-up of 48 months, MAD improved from 80.5 mm medial to 16.1 mm medial (P < 0.0001) and LLD improved from 19.6 to 10.9 mm (P=0.0002). During the same time period, the BMI increased from 35 (95% confidence interval, 32-37) to 38 (95% confidence interval, 35-41; P=0.0006). Compared with their preoperative BMI, 76% of the children had an increase in their BMI at the latest follow-up. There was no association of the change in the patient's BMI with their age of disease onset, sex, ethnicity, health insurance status, final MAD, or LLD. There was a tendency for the patient's BMI to increase with longer follow-up (P=0.002). Using multivariate analysis, only the length of follow-up was associated with an increase in BMI (P=0.026). Conclusions: Despite improvement in limb alignment and LLD after surgery, the BMI of the majority of children with Blount disease increased over time. Other strategies for addressing obesity amongst these children are warranted. Level of Evidence: Level IV-case series.