Sawing casts off

So I’m watching Long Way Down, and when Ewan goes in to get his cast taken off, he asks the nurse/technician what’s going to stop the saw from cutting through his leg, and she replies that it’s an “oscillating saw” and then puts it up to her hand a few times with no ill effect. The next shot is it cutting through the cast.

Now I’ve looked up what an oscillating saw is (“An oscillating blade in an electrical or compressed gas-driven unit; used to cut bone”) and it does not explain how this cuts through the cast but not her skin.

So, what’s the mechanism here?

It’s a blunt blade that vibrates - the vibration locally crumbles the plaster, cutting it. Skin is not affected because of its resilience and elasticity - it just vibrates along with the blade, whereas brittle plaster breaks.

Do they still use plaster? I had a cast in…um… 1989 and it was fiberglass.

It will absolutely cut skin. My doctor didn’t believe me when I said it hurt. when he pealed back the first part of the cast there was a nice cut all the way down. He jammed a ruler under the remaining cast while he finished cutting.

I think that most orthopedic surgeons use resin casts since it elimiates the risk of having the cast fall apart in water. That said, a local medical supply had plaster wrap in stock when I needed it for an art project. Apparently someone is still using it.

She repeatedly puts it up against her hand and nothing happens.

8 inches of my own bleeding skin would suggest otherwise. It’s a vibrating saw with teeth and everything. You gently touch it, nothing happens. Press down and it cuts. There’s a version of it for cutting trim work that’s great for cutting wood trim in place.

The best way to cut a cast is to cut most of the way through with the vibrating saw and then use industrial scissors.

OK. It’s not supposed to cut skin - and I would imagine that in the majority of cases, it doesn’t.

It’s BS. That thing’s also called an autopsy saw.

They mostly don’t cut skin because doctors mostly know what they’re doing. Well, that and there’s a pad inside the cast that snags the teeth of the saw and oscillates along with it, an effect that wouldn’t work with a rotating saw.

When I was a kid, I had a cast cut off. The doctor assured me the vibrating disk attached to the vacuum cleaner wouldn’t cut my skin. He was wrong. Subsequent casts were cut off with what looked like a cross between bolt cutters and channel locks.

Probably not, but the saws aren’t necessarily as safe as they’d like you to think.

My son broke his leg in 2001. When it came time to remove the cast, he was freaked out by the saw, so the doctor did the whole touching it to his hand demonstration. The doctor proceeded to cut the cast off, while ignoring the protestations of pain. When it was finished, while we were able to say that the saw hadn’t actually cut my son, we were less than pleased to notice that the friction of the saw had burnt his leg. He had a 2cm linear burn that is now a 2cm linear scar.

The doctor seemed completely and sincerely shocked, so I’m inclined to think saw injuries are relatively rare. My son, who was 6, just said, “I ***told ***you it hurt,” rather indignantly.

Incidentally, this was done to cut off my son’s fibreglass walking cast. He initially had a plaster cast, but that was removed with large shears. The plaster had deteriorated enough that they didn’t need the saw, but they did have it out to use, just in case.