There is an additional risk that the cages may extrude out of the disc space. If they are placed as an ALIF, the cages can potentially extrude into the abdominal cavity and will need to be retrieved to prevent them from eroding into a major blood vessel. If the cages are placed through a PLIF, the cages can potentially extrude into the spinal canal and can produce significant neural injury. If the cages are placed to the side of the disc rather than in the middle, the cages may impinge on a nerve root. There is also a theoretical risk that the cages could break, although this is unlikely.
Infection is also a remote possibility.
If an infection occurs, the cages need to be removed in order to cure the infection.