Consider the totality of the person. Someone whose health has deteriorated to the point where their bones are so thinned and brittle that they are susceptible to hip fracture has probably deteriorated in general health overall… and may not be receiving regular or competent care in any case. So if they don’t have a physician to recommend a hip replacement, or the constitution to support that major surgery, or the physiology to go through the recovery and rehab afterward… then there are any number of strikes against them. On the other hand, a hip replacement generally indicates (at least as far as this non-physician knows) that it’s “a joint problem” more than an overall skeletal deterioration. So fixing that joint with a replacement can give added mobility and vitality. But if those things aren’t part of the person’s makeup in the first place, then… not so much. Finally, my understanding is that hip fractures generally precede (by seconds) a likely secondary injury that may be fatal in itself. That is, if a person is walking or on stairs and the hip gives way, then there could be an immediate fall that breaks more bones or causes concussion or worse. Finally, someone whose hip has broken is going to be bedridden and that also leads to more complications and general weakening of the entire body.