My father has had to have surgery on his left wrist because the doctor said that part of the bone died. He's fine now, although he can't move his wrist like before. How does part of a bone just die?
Without knowing the specifics of your father's case, we can only give general information about what may have happened. Bone death in the wrist, called avascuar necrosis is caused by lack of blood flow to the specific bone. This could be caused by a trauma, like a fracture, which interferes with the blood flow and doesn't allow the nutrients from the blood to reach the bones. But most often, doctors don't know what causes it.
Usually, a patient goes to see the doctor because his or her wrist is hurting but there doesn't seem to be a reason for it. Then, after examining the wrist and taking x-rays and maybe other tests, the doctor can diagnose the bone cell death, also called osteonecrosis.