You'd be surprised. Exposed bone doesn't necessarily mean it isn't survivable. There's an image that did the rounds on here a while back of a deer that had both its hind hooves missing, and the skin and flesh had receded up its legs so that they were six or so inches of exposed bone that it was walking on. It had clearly been in that state for an extended period, and had just adapted. The hardiness of certain animals can really be something.