Air filled breast expander or saline implant?

Hello I have Mentor CPX expanders now. Filled to 2000cc. I’m happy with them, but one is leaking . I don’t want to go any bigger, so I want to replace them with permanent implants or with other expanders . Around my lower back, I have an infection, so 4 kg on my chest will not help. I prefer less kilograms. Without going smaller. So I would prefer an air or gas filled implant , I read about it that doctors use it, but is it really true?