Electrical treatment and metal implants
For decades there has been a prevailing claim that TENS, EMS, FES and MENS treatments should not be performed near or directly over metal implants. But is there really so much to fear? What is the truth?
As electrical treatments are becoming increasingly common and many devices for home use are available, it is important to know whether these devices carry any risks.
People have long been wary of electricity — partly with good reason. However, the prohibitions related to electrotherapy devices are slowly but surely being overturned!
But let’s look at this step by step!
There are two types of implants
- ACTIVE implants. Devices that operate with a battery or accumulator. Examples include pacemakers, defibrillators, insulin pumps and others.
- PASSIVE implants. Most are used to fix bones, such as intramedullary rods, screws, plates. Entire joint replacements (e.g. knee, hip) can also be made of metal.
Active implants
Active implants operate electrically. A pacemaker or defibrillator, for example, monitors the heart’s electrical activity and, if it detects life-threatening abnormal heart function, it intervenes.
For decades it was assumed that an external electrical impulse (for example from a stimulator) could interfere with these devices. The assumption was that the device’s and the heart’s electrical signals would “merge,” and the interference (the overlapping signals) could cause the pacemaker to sense incorrectly. That is why electrical treatments were prohibited in the presence of an active implant.
In Hungary, most doctors still share this view… but let’s see what others say.
The American Mayo Clinic network is one of the most respected, highest-standard institutions in medicine.
Its researchers already examined this issue in detail in 1988 and published their results under the title “Is transcutaneous electrical nerve stimulation safely applicable in patients with permanent pacemakers?” The study was authored by Mary Jane Rasmussen, R.N.; David L. Hayes, M.D.; Ronald E. Vlietstra, M.B., Ch.B.; and Gudni Thorsteinsson, M.D.
The study summary is as follows:
“We performed transcutaneous electrical nerve stimulation tests in 51 patients who had 20 different types of permanent pacemakers at four anatomical sites — the lumbar region, the cervical spine, the left calf and the upper limb located ipsilateral (on the same side) to the pacemaker. With an average stimulation of 24.7 Hz, no interference, inhibition or reprogramming of pacemakers occurred. The proximity of the stimulation site to the pulse generator had no effect. We did not study electrodes placed parallel to the pacemaker lead vector, a position that has caused concern for others and should probably be avoided until proven safe. Based on our findings, we believe that transcutaneous nerve stimulation can be safely performed in most patients with permanent pacemakers.”
Passive implants
Regarding passive implants (screws, plates and other metal fixations), it was previously assumed that current could be conducted by the metal implant and even heat up, which could harm the tissues surrounding the implant and especially the bone marrow. When this view developed, mainly iron and steel alloys were used for implants and electrotherapy devices were also imperfect.
Since then, the materials used for implants have completely changed, electrotherapy devices have become much more precise, and our knowledge about electricity has grown.
Let’s look at a 2021 study titled “Modeling implanted metals in electrical stimulation applications” by Mercadal, Borja; Salvador, Ricardo; Biagi, Maria; Bartolomei, Fabrice; Wendling, Fabrice; Ruffini, Giulio.
“…our results show that charge transfer between the metal implant and the surrounding tissue is negligible… Metal implants behave as perfect insulators unless sufficient voltage is induced at their interface. If implants are exposed to large electric fields, sufficient voltage will be generated at the interface, allowing charge transfer.”
The bottom line: conventional electrotherapy treatments use very low voltages and currents, to which the metal implant does not meaningfully respond.
Nevertheless, every home electrotherapy device’s manual contains a warning: do not use over an implant. According to current studies, that prohibition is an outdated view!
In my opinion, metal can only cause interference if it ends up between the electrodes (for example, if you have a metal wire in your thigh and you place one electrode on the front and the other on the back of your thigh). Such a treatment is, in fact, a mistake — a faulty electrode placement — and with such incorrect electrode positioning you are essentially trying to bring the current as close to the metal as possible. Even then you are unlikely to harm yourself, but the metal may conduct electricity to an area you didn’t intend to treat.
In summary
Regulations do not allow you to buy medical therapeutic devices for home use that could cause harm.
Electrotherapy, ultrasound, softlaser and similar devices that you can purchase are safe to use. Of course, if you intentionally misuse them, ignore the instructions and use them for a condition they are not intended to treat, that is another matter. With proper use, however, you cannot cause harm!
If you have an active implant (pacemaker, cardioverter defibrillator, etc.), consult your physician. The current view is that electrical treatment may only pose a risk if you place the electrodes directly over or very close to the pacemaker, especially parallel to the pacemaker’s lead wire to the heart. In other words, avoid treating directly over the chest or do so only under medical supervision.
However, if your ankle, hip, knee, lower back, and even your neck, shoulder, elbow or wrist hurt, you can treat those areas safely — observing the general rules of stimulation.
In the case of passive implants, TENS, EMS, MENS, FES and interference treatments do not produce effects — even after prolonged application — that would damage the tissue around the implant.
The current position is that home electrotherapy devices can be used when passive implants are present. Exercise caution when treating directly over an implant, and pay particular attention to correct electrode placement.
If you are unsure about a treatment, seek advice from a physiotherapy professional experienced in electrotherapy treatments.
