The singer / guitarist from Weezer had his legs broken and extended to become taller. Rivers Cuomo was his name. It still is too.
I’d be very surprised if it was to become taller. I’d have to watch the clip again, but I only recall seeing the device stretching his pants on one leg.
I know they’ll do it to fix leg length discrepancies above a certain threshold, especially if the other procedure isn’t viable. I don’t know if there’s other medical reasons to consider it.
One of his legs was a bit longer than the other so he got it fixed; my understanding is it’s incredibly painful so not especially common.
That’s my understanding of the procedure as well. The other method requires more prep but is quite easy.
If they catch it early they can measure how fast each leg is growing at 6 month intervals (and other measurements). Then they can go in and tell the longer leg to stop.
That procedure can be close to painless. A month with a soft cast and crutches, another month with just crutches, and a third month with no physical activity.