Vitamin D and tibiofemoral joint orientation angles in children

Vitamin D is an important component in musculoskeletal development and function in children. The aim of our study was to investigate serum vitamin D levels and tibiofemoral joint orientation angles in children. We performed a retrospective review on a consecutive series of children presenting with lower limb complaints. The children underwent an assessment of serum vitamin D level and full-length standing lower limb anteroposterior radiographs, and were divided into normal and deficient vitamin D groups. Tibiofemoral angles (TFAs) [lateral distal femoral angle (LDFA); medial proximal tibial angle (MPTA)] were measured by three independent observers and compared between the groups. Correlation tests between serum vitamin D level and TFAs were also performed. Sixty (39 boys, 21 girls) children were reviewed. The mean serum vitamin D level for the entire group was 26.8 ng/ml and 75% of the children were deficient. The mean serum vitamin D levels in the normal (11 boys, four girls) and deficient (28 boys, 17 girls) groups were 46.7 ng/ml (range: 32-100) and 20.2 ng/ml (range: 4-29), respectively. The mean right and left LDFAs were significantly higher in the normal compared to the deficient vitamin D group (right LDFA: 98.7° vs. 92.2°, P=0.031; left LDFA: 99.1° vs. 92.6°, P=0.018). We also found a correlation between serum vitamin D level and LDFAs (right ρ=0.29, P=0.03; left ρ=0.30, P=0.02). We found no difference in the right and left MPTAs in the normal and deficient vitamin D groups. In addition, we could not find a correlation between serum vitamin D level and MPTAs. The majority of children were vitamin D deficient. Serum vitamin D level was associated with a change and correlation to the LDFAs compared to MPTAs. Further work is required to investigate the effect of vitamin D supplementation on TFAs in children.