Can teenagers (Under 18) can get limb lengthening?

I've read about it online and supposedly some teenagers are getting limb lengthening. Not for aesthetic purposes of course, usually because one leg is longer then the other.

Is this safe? Aren't they still growing? Apparently your teenage years are the best age to get LL because your bone heals the fastest

yep

Most individuals reach their full adult height by the age of 18, although there is some variation. While most people stop growing by their late teens or early twenties, some may experience continued growth into their early twenties. For those considering limb lengthening, it is advisable to wait until after the age of 19. This is because, if you lengthen one leg to balance it with the other, the untreated leg may still continue to grow, potentially causing an imbalance and making the procedure less effective.

I guess you theoretically could if the growth plates are 100% completely closed. Although, in practice, I am not sure if an LL surgeon would do it for cosmetic purposes on someone under the age of 18.