Hi, thanks for writing to HCM. As per your description, I am taking it granted that extreme means Stage 4 disease process. This is just to inform you that the management of AVN depends on the stage of the disease. In your son s case EXTREME AVN means stage 4, in which case Bone grafting is not going to work. Because during bone grafting procedure only the femoral head is addressed but not the acetabulum (as acetabulum is also damaged in stage 4 disease), so bone grafting will fail inevitably. MRI scan of the hip joint will provide the exact extent of damage inside the joint. IF THERE IS NO INVOLVEMENT OF THE ACETABULUM IN MRI SCAN, then THR is not indicated. Total hip replacement is meant only for stage 4 cases . I suggest you to consult an arthroplasty surgeon and follow his advice accordingly. Hope this information is helpful.