Abstract
Introduction:
Blount's disease can be defined as idiopathic proximal tibial vara. Several etiologies including the mechanical theory have been described. Obesity is the only causative factor proven to be associated with Blount disease.
Varus deformity is also a clinical feature of rickets and 31% of children with vitamin D deficiency rickets presented with varus deformities to the local Metabolic Bone clinics. The aim of this study is to assess if there is an association between vitamin D and Blount's disease. We hypothesize that children with Blount disease are more likely to be vitamin D deficient.
Method:
This a retrospective study of pre-operative and post-operative patients with Blount's disease who were screened for vitamin D deficiency. Patients with known vitamin D deficiency and rickets were excluded. The study patients had the following blood tests: calcium, phosphate, alkaline phosphatase, parathyroid hormone and 25-hydroxyvitamin D. Body mass index (BMI) was also assessed.
Results:
We recruited 50 patients. The mean age of these patients was 10.4 years (SD 3.88) with average BMI of 28.7 (SD 10.2). Fifty two % were overweight. Thirty (60%) patients were diagnosed with infantile, 16(32%) adolescent and 4(8%) juvenile Blount disease.
Eight (16%) patients were found to be vitamin D depleted (less than 20 ng/ml). Of these eight patients, six had insufficient 25-hydroxyvitamin D levels (12–20 ng/ml) and while the other two were vitamin D deficient (less than 12 ng/ml).
Conclusion:
Vitamin D deficiency is a public health problem worldwide. This study confirms that the prevalence of Vitamin D deficiency in children with Blount's disease is similar to healthy children and infants living in Johannesburg. There is no evidence that Vitamin D deficiency is a factor in causing Blount's disease. Routine screening for Vitamin D deficiency in children with Blount disease is not recommended.
