It's not uncommon for adults with a hip replacement to need a revision. Bone fracture around the prosthesis (implant) or loosening of the implant can cause the loss of a good prosthesis.
One or both component parts (ball and socket) can start to sink down into the bone. Infection is another possible cause of implant failure.
The ideal situation is to have one hip replacement that doesn't wear and doesn't have to be removed and replaced. Loss of bone and shortening of one side compared to the other are often problems for patients like your neighbor. Many need to use a walker, cane(s), crutches, or even a wheelchair that they didn't need before the revision.
Fortunately this doesn't happen that often. Only about 10 percent of the patients who need a revision operation are having their third or fourth one. One-third of the patients are undergoing their second revision. Half are having their first revision.