Weight and Infantile Blount Disease

Background: Blount disease is growth disorder of the proximal tibia, resulting in genu varum, internal rotation, and procurvatum. Three different forms of the condition are described: infantile, or early onset, juvenile onset, and adolescent or late onset. Although several hypotheses exist, the etiology of Blount disease remains unknown. The best-founded hypothesis is the "increased mechanical force hypothesis". In particular, the relation between obesity and Blount disease. Although, most studies supporting this hypothesis are conducted in high income countries. However, unlike in the Western population that was studied to establish this hypothesis, Blount disease is relatively common in African countries and obesity is not. Methods: This study is a retrospective, case control study in a rural hospital in Ghana (2012-2021). Demographic information, body weight, and age at presentation were collected. The World Health Organization (WHO) weight-for-age growth standard was used. Overweight was defined as a percentile between 85th and 97th. Obese as a percentile between 97th and 99th. Above the 99th percentile was defined as severely obese. Results: In total 96 patients with infantile Blount disease were included, all of black Ghanaian descent. The mean age of onset of Blount disease in our patients was 1.7 (±0.9) years, and the mean age at presentation was 6.3 (±3.4) years. This was not different between boys (n = 27) and girls (n = 69). The mean weight for age percentile in our population was 56.8th (±35.3th), and 68% was of normal weight, 15% overweight, 8% obese, and 9% severely obese. Our study population had a significant (p < 0.05) higher mean weight percentile compared with the local control group (n = 79, 37.0th ± 26.0th). Conclusion: Although our study population of patients with infantile Blount was significantly heavier compared with the control group, the mean weight (56.8th ± 35.3th) was well within normal values. Obesity might have a role in the development of infantile Blount disease, but it is shown to be not as an important factor in the Ghanaian population (18% obese) compared with the more extensively studied US population with much higher obesity rates. Level of Evidence: Level III. See Instructions for Authors for a complete description of levels of evidence.