Internal Bone Growth Stimulators for Spine Fusion

An internal bone growth stimulator is implanted at the time of the spinal fusion surgery near the site of the fusion.  The goal is to enhance the chance of achieving a successful fusion, and thereby reduce the patient’s pain. 

What to Know about Internal Bone Growth Stimulators

The implanted bone growth stimulator is a small medical device, about the size of a matchbox, that is implanted in a soft pocket of tissue under the skin in the lower back to the side of spine during a lumbar spine fusion. 

The device includes a battery pack attached to wires that lay on top of the site of the bone graft, such as the posterolateral gutter area of the spine. The wires deliver 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 used to help set up the fusion, such as pedicle screws or a cage.  

An implanted electrical stimulator may be used with any type of spine fusion surgery, such as an ALIF, a PLIF, a posterolateral gutter fusion, and other surgical approaches. 

See Postoperative Care for Spinal Fusion Surgery

What Patients Say About the Implanted Bone Growth Stimulator

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. 

The device is usually not noticeable under clothes. 

Patients do not feel any painful or tingling electrical sensations. 

Most patients report that they can go through airport metal detectors without a problem.

Postoperative Instructions for an Internal Bone Growth Stimulator

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, participating in water therapy, any type of bathing will not affect the device. 

Removal of the Device

The implanted device is typically 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. 

The procedure to remove the device 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 place and are not noticeable to the patient.

Potential Risks and Adverse Effects

While internal electrical stimulators are generally considered safe, it is important to note that in certain situations the electromagnetic effects of this type of treatment are unknown or may be problematic.  For example: 

• The effect of bone growth stimulation during pregnancy or nursing is not known 
• The electrical current may impact some types of pacemakers and defibrillators. 
• The device may not allow for an MRI scan to be done
• The procedure carries a small risk of infection 
• Some people report feeling discomfort at the site of the device 
• Some people may have an immune reaction to the implanted device

This list is not comprehensive, and patients are advised to discuss the specific risks and their individual situation with their doctors.

Pros and Cons of Implanted Bone Growth Stimulator

One main advantage of an internal bone growth stimulator over a device that is worn externally 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.

The main disadvantages are related to the fact that the device is surgically implanted, for example:

• A second surgery is required to remove the device.  While this is a minor procedure and is done on an outpatient basis, it is still a surgery and carries some degree of risk.
• The patient may not be able to have an MRI scan done. 

Finally, using an internal bone growth stimulator adds an extra cost to the spine fusion.  This cost is typically covered by most insurance plans, but not all.  For many people considering spine fusion surgery, the likelihood of improved fusion results and reduced pain may make it worth the added cost.