Remember that scene in Younger season two, episode seven, where Diana Trout broke a man’s penis?
Of course you do, it’s impossible to unsee.

However if you blanked or blurred out the details out of sheer fear, let me refresh your memory.
Diana is getting it on with one of her authors, male feminist Hugh Shirley, when whilst on top she leans back "like a Romanian gymnast" only to hear a loud crack.

It's not her back. Shirley's penis has been broken.
The technical name for it is "Penile Fracture" and it happens when an erect penis comes into contact with with significant force. This leads to pressure overload, which the internal tissue holding the pressure can't contain anymore, so it ruptures.