The present invention includes a method and devices for treating osteonecrosis in, e.g., children, adolescents, and adults comprising: identifying a subject in need of treatment for osteonecrosis； drilling two or more holes into a bone in need of treatment for osteonecrosis； inserting two or more needles or cannulas into the holes in the bone； washing an interior of the bone with a washing fluid introduced through one or more of the needles or cannulas inserted into the bone； and after washing the interior of the bone introducing one or more bone growth promoting materials or cells into the bone.
