The condition of bone grafts is difficult to assess from X-rays. Studies of X-ray findings compared with autopsies would be helpful in answering this question.
For example, if you had X-rays taken periodically throughout the rest of your life as a baseline, scientists could compare these tests with how the bone and hip actually look during autopsy after death. Such studies to report the fate of bone grafts just haven't been done yet.
In the normal biology of bone grafting, we know that healing of the host tissue can begin as early as two days after implantation. New (native or natural) bone growth can be seen by four weeks. The rate of bone growth is often slower when donor bone from a bone bank is used for the graft.
PET scans can be used to assess blood flow to the graft site but this is costly and not used routinely with patients. X-rays may not show the condition of the graft but they do usually show any problems that may be developing. For this reason, X-rays are still the first choice for assessing graft condition.