Study Design. Four cases in which, during standard laminectomies, knife blades broke deep into the disc space are reported. Summary of Background Data. These broken knife blades could not be removed at the time of initial operations. Results. Follow-up studies indicated further anterior migration of retained fragments in two cases after ambulation. Conclusions. Because of the potential hazards of late intraabdominal visceral or vascular injuries, removal of sharp retained fragments at another session is recommended.