Foot Drop. Any operation around the lumbar spinal canal can put nerve roots at risk. The most common levels are between l4/l5 and l5/s1. The nerves at these levels control calf muscles responsible for raising or lowering the toes and although new weakness or paralysis is not common, there will always be a small potential risk.
No. But that does not make it impossible. Any operation on the nerves can cause weakness. Loss of movement sounds like paralysis and that is exceedingly rare.