Data from two studies including 52 patients with avascular necrosis of the femoral heads and 76 patients without such feature a higher pooled prevalence of the MTHFR TT genotype in the latter group (3.9% vs. 1.97%, p = 0.66) with no heterogeneity (I2 = 0) [plot not shown]. This evidence concerns the gene MTHFR and avascular necrosis.