I had an L5-S1 posterior/ anterior fusion 9 months ago. It failed and I am in for a second fusion of L4-S1 this time. On a recent CT scan and x-ray, it shows what they call "Halos". There is empty space between the screws and bone from where the screws are grinding against the bone when I move. OUCH! I am afraid that, because they are no longer tightly in place, that they will come out! Could this happen? What should I do if I notice a little lump in my back. Please help!