The FDA has laid out the ethical groundwork: if a patient has no other options, a safe (sterile) surgery may be performed. It's only because they revoked his approval to use the specific type of implant. Would it really require so much money to demonstrate sterility? Or did Kennedy just not want to have to deal with bureaucracy and barely functional/dying patients and therefore took matters into his own hands? If so I don't blame him; if you can't communicate with your subject it's hard to make sure everything is being done right.
To Kennedy, he had no other options.