Bone Stimulators

Bone growth and fusion in a surgically treated spinal segment can be stimulated by specialized medical devices called bone stimulators, which emit low-voltage electric currents. The newly formed bone grows in the interbody space and fuses the treated spinal segments.

Bone stimulators can either be implanted (internal) or worn outside the body (external). There are 3 different types of electrical stimulation:

1. Direct current stimulation
2. Pulsed electromagnetic field stimulation
3. Capacitive coupled electrical stimulation

Due to high costs and inconsistent results, only 32% of spine surgeons use bone stimulators to enhance spinal fusion in their patients. ¹ Bhavsar MB, Han Z, DeCoster T, Leppik L, Costa Oliveira KM, Barker JH. Electrical stimulation-based bone fracture treatment, if it works so well why do not more surgeons use it?. Eur J Trauma Emerg Surg. 2020;46(2):245-264. doi:10.1007/s00068-019-01127-z

Internal Bone Stimulators

The internal bone stimulators are implanted in the body and have a battery pack that is placed under the skin. The wires of the device lay on top of the transverse processes (a muscle attachment site on the left and right sides of each vertebra) in the posterolateral gutter (the area just outside the spine).

The battery pack creates a lump under the skin and can be removed after 6 to 12 months, when adequate bone growth and fusion have been stimulated. Removing the pack is a simple procedure and is done under local anesthesia.

Read more about Internal Bone Growth Stimulators for Spine Fusion

External Bone Stimulators

The external bone stimulators can be worn by the patient on their skin either as thin pads taped over the fusion site or as a brace containing coils. These external stimulators need to be in contact with the body for specific periods of time throughout the day. As this setup may be inconvenient to some patients, the rate of patient compliance in wearing this device may be low, although some products have software that can monitor compliance.

Read more about External Bone Growth Stimulators for Spine Fusion

Bone stimulators are typically employed for patients who have a lower likelihood of obtaining a solid fusion, such as in multilevel fusions, revision surgery (after a failed fusion), or for smokers. Both internal and external stimulators are expensive but can be worth the expense for patients who need extra help, such as women with osteoporosis. ² Andersen T, Christensen FB, Langdahl BL, et al. Fusion mass bone quality after uninstrumented spinal fusion in older patients. Eur Spine J. 2010;19(12):2200-2208. doi:10.1007/s00586-010-1373-2 Commercial and government insurances typically cover external stimulation for patients with risk factors who undergo multi-level fusions. Patients are advised to check their benefits with their insurance provider.

Read more about How an Electrical Bone Growth Stimulator Helps with Spine Fusion

Platelet-Rich Plasma

A more recent technique to stimulate bone growth and spinal fusion involves the use of platelet-rich plasma. Plasma is a colorless liquid derived from the blood after the blood is centrifuged (spun down at a high speed). Blood plasma contains growth factors that may help to promote the formation of bone after surgery.

This technique is still being studied in clinical studies and using animal models; further research is needed before drawing conclusions on its effectiveness. The most recent research indicates that platelet-rich plasma has limited benefits, or no benefits, in the success of spinal fusion and pain relief after surgery. ³ Muthu S, Jeyaraman M, Ganie PA, Khanna M. Is Platelet-Rich Plasma Effective in Enhancing Spinal Fusion? Systematic Overview of Overlapping Meta-Analyses. Global Spine J. 2022;12(2):333-342. doi:10.1177/2192568220988278 ^{, 4} Cai YF, Tian TZ, Chen LY, et al. The effect of platelet-rich plasma on the fusion rate and clinical outcome of spinal fusion surgery: A systematic review and meta-analysis. PLoS One. 2020;15(12):e0243204. Published 2020 Dec 3. doi:10.1371/journal.pone.0243204

Other ways to enhance or promote bone fusion include the use of osteoporosis drugs and the possible use of controlled-release formulations in the future. ⁵ Zhang Y, Jiang Y, Zou D, Yuan B, Ke HZ, Li W. Therapeutics for enhancement of spinal fusion: A mini review. J Orthop Translat. 2021;31:73-79. Published 2021 Dec 6. doi:10.1016/j.jot.2021.11.001 Advanced methods of bone stimulation continue to be researched and developed.