Most likely you can replace the damaged posts. It's normal to attach the post to concrete with a bracket, or a bolt. The replacement posts must be treated, never use cedar or redwood in contact with cement. You will need to build a temporary support for the weight of the stairs, remove the old posts, then inspect the concrete. Make sure the concrete slopes away from the post to avoid water sitting at the wood. If the concrete is OK you could drill a hole, attach new brackets and new posts. If this is a wet area, it might help to seal the cut ends of the post before installing, once again keep mosisture out of the wood. Good Luck.