You need to get with a medical malpractice attorney and have them send a preservation letter instructing them not to destroy or dispose of the screws.  From there, the attorney can also help you procure your medical records which should document the need for the second surgery and the condition of the screws.  From there, they can help you make a decision on whether to file a medical malpractice claim or a product liability claim (or some combination thereof).  Considering the response that you have received so far, you need to get this moving now before they dispose of the screws.