New Bone Growth Stimulation Devices for Spine Fusion

More recently, two other non-invasive technologies—external bone growth stimulators—have been approved for use as an adjunct to improving the success for spinal fusion. Much like the pulsed electromagnetic field (PEMFs) device, the capacitive coupling (CC) and combined magnetic field (CMF) devices are worn externally, and are used for up to nine months after the spine fusion surgery.

Capacitive Coupling (CC) for spine fusion:

The newest entry into the spinal fusion bone growth stimulation market is capacitive coupling. This device was FDA-approved in 2000 and is indicated as an adjunct to enhance the clinical success for primary (one and two-level) lumbar spinal fusion.

Incorporating capacitive coupling technology into the smallest, lightest non-invasive bone growth stimulator available, it stimulates a continuous biological response. Worn 24 hours a day, two small, wafer-thin skin pads/electrodes are placed directly onto the skin over the fusion site.

Like other bone growth stimulation devices, the precise mechanisms of action, which promote healing, are not completely known. Published basic science has shown the capacitive coupling demonstrates a biological response.¹⁵

The concept of using capacitive coupling as an adjunct to lumbar spine fusion is relatively new. One study has been published to date.¹⁸ While CC has been commercially available since the early 1990’s for non-union fractures, efficacy in spinal fusion has (only) recently been demonstrated in a multi-center randomized double-blind study. The overall success rate of the stimulated patients (84%) compared to the non-stimulated patients (64%) was statistically significant. Of the groups used to stratify the data, four of seven, showed statistical significance between the actively stimulated patients and the placebo patients.

Combined magnetic fields (CMF) for spine fusion:

Unlike the PEMFs device, the CMF device delivers a time varying magnetic field by superimposing the time-varying magnetic field onto an additional static magnetic field. The device is usually worn for 30 minutes daily. The rationale for the combined field with 30 minute per day treatment was based on animal data, which demonstrated increased bone stiffness at the 30-minute dose. However, the treatment effect was far greater in this animal model with 24-hour per day treatment, indicating a dose response. In addition, a comparison of pulsed electromagnetic field (PEMF) with combined magnetic fields (CMF) in a rabbit tibial osteotomy model showed the two signals to be very similar at equal treatment times.¹⁶

The latest clinical study examining the use of adjunctive combined magnetic fields to enhance non-instrumented posterolateral spinal fusion was reported at the American Association of Orthopedic Surgeons 2000 meeting.¹⁷ The series revealed an overall success rate of 64% in the stimulated group compared to 43% in the control group. In this clinical trial, combined magnetic fields appeared to only be effective in women, with no improvement in fusion rates among men. There are no other published scientific studies documenting the clinical efficacy of combined magnetic fields.