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  • Author Author: ninjatrent
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Combined Magnetic Field Bone Growth Stimulation Device - Teardown

ninjatrent

A few years ago, I underwent a surgical procedure called a Spinal Fusion. Afterwards a special medical device was prescribed to assist with the fusion process. This device is called a Combined Magnetic Field Bone Growth Stimulator.

 

The little kid in me has been eager to see the inner workings of this device. It was only a matter of time before it would be taken apart.

 

Here are some photos of what was found inside.

 

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Device Description

 

The SpinaLogicRegistered bone growth stimulator (DJO, Vista, CA) consists of a three-dimensional patient interface contoured to follow the curvature of the lumbar spine, a control box containing the electronics, and a battery pack . The device is used for 30 consecutive minutes a day until fusion occurs as determined by the treating physician. The patient interface consists of a single transducer coil to generate the magnetic field and a magnetoresistive element to provide feedback as to the magnitude of the earth’s magnetic field which ranges from 25 to 65 microTesla (μT). The coil is constructed using 504 turns of 30-gauge copper magnetic wire.

 

When the specified current is applied to the coil, it generates an extremely low-frequency and extremely low-intensity magnetic field that has both alternating and direct current (AC and DC) components, labelled a combined magnetic field (CMF). Specifically, the field oscillates sinusoidally at a frequency of 76.6 Hertz with an AC component of 40.0 ± 8.0 μT, peak to peak, and a DC component of 20.0 ± 2.0 μT.

 

The source for this information.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4779460/

 

  • in reply to ninjatrent

    Interesting article, but clearly the use of these machines has a long way to go before anyone can definitively say they work and on what level of bone fracture.

     

    So far the sample set is too small to make any recommendations and given the wealth of other factors that may have an impact I would remain skeptical.

     

     

     

    DAB

  • in reply to DAB

    I don't have an oscilloscope to investigate what is happening when active. From what I read it generates a certain frequency magnetic field from the coil that stimulates the mechanism that causes natural bone repair. I might be able to use a magnetometer to detect any field generated or a Software Defined Radio dongle to see if it generates anything in radio frequencies. Damage to my PC Hard Drive was a concern when in operation.

     

    Here is an article I found on devices of this type. The one that I have generates a Combined Magnetic Field.

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2762251/

     

     

    It appears to be a very complex circuit. I will have to locate information on the components. It is doubtful there will be any schematics. The coil only has two wires. But there is a chip of some type that is located in the center of the coil (not attached) that has wires connected. Very strange device.

     

    The coil might easily be repurposed into something else. Might be 12" diameter coil made of 504 turns of copper magnetic wire. A metal detector would be an interesting project. Maybe a small hand wound motor would be fun.

     

    I will do some research on the individual chips and post findings soon. Thanks for checking out this post.

     

    Trent

  • in reply to michaelkellett

    Yes, evidently doing electroshock therapy is back in vogue.

     

    I have used the electro-stimulators for muscles and they were OK, until the fool using the other channel decided he needed a higher setting and over excited my neck muscles.  I was in a lot of pain for many hours.

     

    I told him if he ever touched he controls again I would beat the crap out of him.

     

    Luckily the people who ran the joint went one better, they banned him from the machine entirely.

     

    DAB

  • in reply to DAB

    There is  a complete sub culture of this type of snake oil medical science.

    If you google about a bit you can find lots. I got interested in it  (as one might be interested in crime) when I was asked to build one (I declined).

     

    Here is a sample: The Zapper!

     

    MK

  • in reply to ninjatrent

    Interesting, have considered doing a reverse engineering on the circuit.

     

    I am curious about all the components.  Are they doing specific frequencies, voltage levels, pulse forming or what?

     

    They have clearly made a complex circuit, could the stimulation process really be hat complex?

     

    DAB