Body mass index and Blount's disease: a single academic hospital experience

Abstract

BACKROUND: Blount’s disease is a developmental disorder of the proximal tibia with progressive varus, flexion and internal rotation deformity. It is often seen in overweight children and strongly associated with obesity. As the prevalence of childhood obesity is increasing worldwide, the incidence of Blount’s disease has been noted to be on the increase as well. In the South African population, most children are malnourished with high levels of undernutrition compared to other middle-income countries. We hypothesised that in our institution, patients with Blount’s disease have a body mass index (BMI) lower than reported in studies from mainly developed countries. The aim of the study was to investigate the relationship between BMI and Blount’s disease in a South African academic institution. METHODS: All clinical and radiological records of patients with Blount’s disease at a tertiary hospital in South Africa over a six-year period were retrospectively reviewed. Five patients did not meet inclusion criteria and were excluded from the study. Data collected included patients’ demographics, weight, height and radiological investigations. A control group of randomly selected paediatric orthopaedic patients was studied. RESULTS: A total of 39 Blount’s patients (19 females, 20 male) were studied. All the Blount’s patients were of black ethnicity. There were nine patients with early-onset and 30 patients with late-onset Blount’s disease. The mean BMIs for Blount’s disease and control groups were 26 kg/m² and 20 kg/m² respectively (p<0.001). There was no statistical difference in sex, laterality, BMI and BMI-percentiles (BMI%) between early-onset and late-onset Blount’s disease. There was no relationship between BMI and severity of Blount’s disease deformities. CONCLUSION: High BMI is associated with Blount’s disease in the cohort studied. There was no relationship between increasing BMI and severity of Blount’s deformities. No relationship was found between sex, onset or laterality and Blount’s disease in our study.