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.
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