Ileum refers to a portion of the small intestine. Ilium refers to a bone in the pelvis. Although the ilium is not a long bone, the point is to make an association. Occasionally a doctor will provide you with the spelling of a term or medication. Although they may be correct it is recommended that you verify their spelling before making it a permanent part of the patient's record.
Many doctors make mistakes when it comes to spelling.
Take a 5 minute break every 45 minutes or so, use a quality office chair, and be sure to use a wrist rest with your keyboard.