PLIF or posterior lumbar interbody fusion is considered one of the best ways to fuse the spine. The disc is removed along with the facet joint giving the nerves plenty of room. Bone from that is removed is used for the graft. Fusion rate is fairly high for this method.
Hardware failure such as screws breaking or slipping doesn't doom the patient to a failed fusion. Often the patient wouldn't know there was a problem if they didn't see it on X-rays. There is no pain or change in function or activity.
The surgeon will probably follow you a little more closely with X-rays and possibly CT scans. If there are any signs of nerve compression, then a second (revision) surgery may be needed.