From the research I was able to do yesterday, the answer is for you to run a very strong course of anti-biotics. If it is possible, you need to be hospitalized and give a really good course of ansef along with pain meds that are more easily controllable in the hospital.
After you are deemed infection free, I would highly recommend having a new surgery to remove the bad harrington rods and possibly have a different material used for implant. It seems as though your body has chosen to reject the metal used for your implant and you need to get it out and have a different material used.
Yes, it is a risk and the pain may not be fruitful but the chance that you will heal and get back on course for your md treatment. I cannot comprehend how bad it feels for you but remember it can get better.
Good luck and keep us updated as to your progress.