An internal bone growth stimulator is implanted at the time of the spinal fusion surgery. This device is quite small and is implanted in a soft pocket of tissue under the skin in the lower back to the side of spine. It delivers small electrical currents directly to the area in the spine where bone growth (the spine fusion) is to occur.
An implanted stimulator may be used with or without any other devices related to the fusion, such as pedicle screws or a cage, and is unrelated to the spine surgeon's choice of which technique to use for the spine fusion surgery .
Some patients report that they can feel the internal bone growth stimulator under the skin when they touch the area, and some say that they do not notice it at all. It is usually not noticeable under clothes. The devices do not create any painful or electrical sensations.
There are no special activity restrictions for patients with an implanted electrical stimulator; however, many surgeons will restrict their patient's activities because of the fusion surgery. Swimming and bathing will not affect the device. Most patients report that they can go through airport metal detectors without any problem.
The implanted device may be removed at the end of its useful life (e.g. six to twelve months after implantation), depending on the surgeon's and the patient's preference. If the spine surgeon removes the device, the procedure is usually done through a small incision in the lower back as an outpatient procedure with IV sedation. The small wires on top of the fusion site are usually left in and are not noticeable to the patient.
While internal electrical stimulators are considered very safe, it is important to note that the electromagnetic effects of this type of treatment are unknown for pregnant women, and for some types of pacemakers and defibrillators.
Other Considerations for Bone Growth and Spine Fusion
A theoretical advantage of an internal bone growth stimulator over external devices is that patients obviously cannot remove the device, and therefore there is 100% patient compliance with using it and the full benefit of the treatment can be realized.
One drawback is that it the implantable stimulator adds extra cost to the spinal fusion procedure. Use of these devices are often considered cost effective, however, as they increase the chances of obtaining a successful fusion.