My husband was in a car wreck back in '99 and fractured his spine in 3 places. Rods and pedicle screws were put in, but they kept coming loose and had to be replaced. At that time, they put in what they told us was a battery to stimulate the bone. At some point, the screws came loose again, and he developed severe back pain and huge basketball-sized squishy lumps on his back. He saw orthopedic surgeons who took samples of the fluid inside and they told him they had no idea what it was. He went on like this for almost 10 years. Finally, a doctor referred him to a Neurosurgeon who took one look and said he needed surgery immediately. The next day he was in surgery and after the surgeon said he couldn't figure out how my husband was still alive. All of the hardware was removed, and the battery was leaking. He had to have bone grafts and tissue grafts. He had MRSA, Sepsis, Septic Shock, and Osteomyelitis. He was hospitalized for 3 weeks as they weren't sure he would make it.
He still has pain and all they were giving him was tramadol. He finally had it out with them and they ordered oxycodone. But even that just takes the edge off.
I would never ever recommend those stimulators. As you said, it can cost you your life.