get a limb amputated due to infection/etc? basic wooden prosthesis should be a option with somewhat slightly more advanced prosthesis being available late game.
wood would work temporarily for lost legs or arms.
i assume you could have a metal spike arm prosthesis for stabbing zombies to death.
but basic wood ones would be good enough.
and if NPC's are added you would need a surgeon/doctor to preform this operation in a adequate room.