If you are a doctor you also know that a mandible, like our own one, will not actually be attached by bone to the skull or even cartilage, especially with the articulation the Predators show it is obvious they are segmented into several pieces.
It is probably more comparable to tearing a finger apart, that already suffered pretty severe damage, or the claw of a crab if we are going crustacean instead of mammalian in terms of biology.
Totally doable.