Ultrasound therapy and metal implant

[chovik]

I haven't seen any valid research that actually says US is of any use at all. Causing pain due to applying over metal does not validate that US is, or would have been, of any use in the first place

[RTP]

I agree, there's insufficient evidence to say that ultrasound is of use. That doesn't necessarily mean that it's useless, but rather just that no-one has (as yet) been able to prove that it's beneficial. Having said that, I never use ultrasound in my clinic.

However, ultrasound over implants is ALWAYS going to be a bad idea, not because it heats the implant itself, but because too much heat is deposited into too small a volume of soft tissue. Normally when we use ultrasound, the "energy" of the vibration is slowly absorbed over a 3-4cm depth of soft tissue, meaning that the heat is distributed and the resulting heat effect isn't going to be too intense in any 1 spot. If there's an implant, the sudden change in density at the soft tissue/implant border means that the vibration can't carry across from one into the other, which means that all the remaining "energy" of the original vibration will be dumped into the tissues just before the implant. In other words, the tissues immediately superficial to the implant get too hot, and this can cause a burn. Unfortunately, since the burn is inside the body, you may not be able to see any sign of it on the skin at all. Best thing to do is explain the risks to your client (patient) and make sure they understand the importance of telling you immediately if they feel any heat concentrating in any 1 spot. Or better yet, use another modality, like scar massage?

[AussiePhysio]

I thoroughly agree with RTP's reply

WHY do we use u/s so much? - we have so many better options.

basic u/s physics will tell you that a soft tisue/metal interface = reflection of sound energy from the sound head (instead of absorption or transmission of the enery. This means the soft tissue surrounding the metal gets an extra (reflected) dose of sound energy, heating adjacent tissues much more quickly and possibly burning them. Thats one possible mechanism for pain from U/S around highly reflective areas.

The metal is not what gets hot as far as i have been taught- it's the tissue immediately adjacent.

At any rate, there is little evidence to support the use of ultrasound for most conditions it has been studied in - so does the risk outway the benefit?

we have far better tools to use than U/S