Fractures and severed limbs cause cuffs to fall off

Handcuffs fall off if your hands or arms get severed. Likewise, leg cuffs drop if your feet or legs do.
Fractures in these limbs have a 25% chance to cause cuffs to fall off.

While restrained, if you switch to "harm" intent with "mouth" selected, you can click on yourself to chew through your own wrists. You can use this to fracture your active hand, but it's not guaranteed to free you and even if it does you'll probably pass out from shock/blood loss in a minute.

There's a graphical glitch where the cuffs still appear in your inventory after they've dropped (you can pick them up to fix the glitch) but this happens even if the cuffs fall off for other reasons and I couldn't figure out how to fix it. Something to do with the effect/equip_e object? I didn't really understand that code otherwise I would have fixed that as well.