Managing this kind of problem depends on several things. First, does the X-ray show the cage is fractured, but still stable? In other words, has the cage shifted or moved in any way? Second are you having any bothersome pain or other symptoms? Third, is there any sign of spinal deformity developing?
The cage may be left in place if there's no sign of shifting or nonunion of the bone graft. The cage should be in the center. A slight shift in one direction or another is okay. Another option is to remove the cage and reinsert another cage. Sometimes the surgeon reinforces the area with a metal plate or screws.