The Effect of Socioeconomic Deprivation on Radiographic Deformities in Children With Blount Disease.

BACKGROUND: Blount disease can occur at any time during the growth process, primarily with a bimodal distribution in children younger than 4 years old and adolescents. The disease process most commonly presents in Black adolescents, with disease severity positively correlated with obesity. Given the known associations among race, obesity, and socioeconomic status, we investigated the relationship between the degree of social deprivation and severity of lower extremity deformities among a community-based cohort with Blount disease.

METHODS: A retrospective review of hospital records and radiographs of patients with previously untreated Blount disease was conducted. Patients were classified as having early-onset or late-onset Blount disease based on whether the lower limb deformity was noted before or after the age of 4 years. The area deprivation index (ADI), a nationally validated measure that assesses socioeconomic deprivation by residential neighborhood, was calculated for each patient as a surrogate for socioeconomic status. Higher state (range: 1 to 10) or national (range: 1 to 100) ADI corresponds to increased social deprivation. Full-length standing radiographs from index clinic visits were evaluated by 2 reviewers to measure frontal plane deformity. The association of ADI with various demographic and radiographic parameters was then analyzed.

RESULTS: Of the 65 patients with Blount disease, 48 (74%) children were Black and 17 (26%) were non-black children. Nineteen children (32 limbs) had early-onset and 46 children (62 limbs) had late-onset disease. Black patients had significantly higher mean state (7.6 vs. 5.4, P=0.009) and national (55.1 vs. 37.4, P=0.002) ADI values than non-black patients. Patients with severe socioeconomic deprivation had significantly greater mechanical axis deviation (66 mm vs. 51 mm, P=0.008). After controlling demographic and socioeconomic factors, the results of multivariate linear regression showed that only increased body mass index (β=0.19, 95% CI: 0.12-0.26, P<.001) and state ADI (β=0.021, 95% CI: 0.01-0.53, P=.043) were independently associated with greater varus deformity.

CONCLUSIONS: Socioeconomic deprivation was strongly associated with increased severity of varus deformity in children with late-onset Blount disease. Our analysis suggests that obesity and socioeconomic factors are the most influential with regard to disease progression.

LEVEL OF EVIDENCE: Level III.