Bone stimulators, which emit low electrical currents, can be used to stimulate bone growth and enhance the spinal fusion. Bone stimulators can either be implanted (internal) or worn on the outside of the spine (external).
The internal bone stimulators have a battery pack that is placed under the skin, with wires that lay on top of the transverse processes (a muscle attachment site) in the posterolateral gutter.
Generally, patients will want the battery pack removed at a later date (after six to twelve months) because it creates a lump under the skin. Removing the pack is a simple procedure that is done under local anesthesia.
The external bone stimulators do not require a separate procedure for removal, but carry the added inconvenience for patients of having to wear an external appliance. Some physicians also question the rate of patient compliance with wearing this device, although some products have software that can monitor compliance.
Bone stimulators are most typically employed for patients who have a lower likelihood of obtaining a solid fusion, such as for patients with multilevel fusions, revision surgery (after a failed fusion), or for smokers. Both internal and external stimulators are expensive ($3,000-$5,000), but they can be worth the expense if they help result in solid fusions for patients who need the extra help.