Well, they did a technical test of that among other inquisitorial torture devices on a science channel, and their conclusion was that the pear was probably never used sucessfully since the materials and metallurgy that was availiable at the time couldn't make the petals nor the joints of the pear strong enough to handle the reactive forces from the victim's body tissues as the screw was turned and thus the pear would break long before the victim was injured.
Either way, Ronin, it's funny you feel so enraged for the female victims, but not for the male homosexuals who were just as cruelly persecuted if found out.