The findings revealed that 16 gut microbial species and their metabolic pathways, including genus Eggerthella and the superpathway of sulfate assimilation and cysteine biosynthesis of the gut microbiota, and 23 immunophenotypes, such as the absolute count of CD33− HLA DR + Myeloid cell and T cell %lymphocyte, demonstrated a causal relationship with osteonecrosis. This evidence concerns the gene CD33 and osteonecrosis.