This is substantial equivalence?

The type of device which the FDA has called "Diathermy, shortwave, for use other than applying therapeutic deep heat" (Product Code ILX) has been of particular interest to me since 1976, during my employment in the Bureau of Medical Devices, FDA.

The archetype of this type of device was first introduced into the market around 1959, and was promoted as a therapeutic device for wound healing.  The FDA found fault with the labeling, culminating in an injunction in 1972 prohibiting the company from selling its product in interstate commerce.

More years of litigation ensued.  Meanwhile, the FDA caused hundreds of the devices to be seized from doctors' offices and clinics around the country.  Most devices were destroyed or buried in landfills.

Finally, the company prevailed - sort of - and was permitted to resume sales in the U.S. with a very limited label: The device could be promoted as an adjunctive therapy for the mitigation of pain and edema in superficial soft tissue.  The company resumed marketing in the U.S. in 1987.

Because the product had been in distribution before 1976, it is considered to be a pre-enactment device.  This is important because at least one other company used this product as a predicate in a 510(k).

The company has always maintained that their product is not shortwave diathermy despite its similarity to diathermy.  What distinguishes this machine from conventional diathermy is that the output is pulsed.  The output pulses are 65 microseconds long.  Although the peak power is 975 watts, the maximum average power is only 38 watts.

The FDA has always maintained that the product is shortwave diathermy.

The device, in case you haven't guessed yet, is Diapulse.   

FDA's argument concerning Diapulse is rather simple.  They consider it to be a diathermy device.  But diathermy devices are required to be capable of elevating the temperature in the treated body part to 104 deg F within 20 minutes.  FDA "experts" did not know of any therapeutic effect of radio-frequency energy aside from the heating effect.  Diapulse does not deliver  enough power to the patient to meet the criterion for diathermy.  Therefore, Diapulse was thought to be ineffective and was declared a quack device.

Research using Diapulse has amply demonstrated not only its effectiveness, but its superiority to conventional diathermy.  See the annotated bibliography for details.

A number of manufacturers have submitted 510(k) notices for ILX devices, with Diapulse as the original predicate device.

The table below shows the companies and products cleared under 510(k) notifications in device category ILX between 1991 and 2009.

MFR               510(k)    PREDICATE             CLEARED
MRT            K903675    Diapulse®                01/17/1991
Regenesis   K972093    MRT SofPulse         10/21/1997
PAW            K022404    MRT SofPulse          08/08/2002
ProMedTek K070931    MRT SofPulse          05/24/2007
Ivivi Tech.   K070541    MRT SofPulse           12/11/2008
OrthoCor    K091996   Ivivi Tech. Torino II      12/15/2009

The next table lists the maximum peak powers for some of the devices in the prior table.

Ivivi Technologies' 510(k) actually covered three devices listed below.
(Regenesis and PAW devices are excluded from the table.)

Manufacturer          Device Peak    Power, Watts
Diapulse Corp.         Diapulse®               975
MRT                         SofPulse                  400
Ivivi Technologies9   912-M10                   10
                                Roma                        10
                               Torino II                       1.8
ProMedTek              PMT850                     0.043
OrthoCor                 Knee System      6.5 p.Ws/cm3

CDRH determined all of these devices to be substantially equivalent to their respective predicates.

Clearly, CDRH reviewers were convinced by the evidence presented in these 510(k)s that the devices were substantially equivalent despite the huge decrease in peak power.  Because the 510(k) notices obtained under FOI were so heavily redacted, I could not tell what experimental evidence or theoretical argument convinced CDRH reviewers that these were substantially equivalent.

Somehow, it seems to defy common sense that devices are "substantially equivalent" when a key parameter has decreased by orders of magnitude!

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