Had laminectomy surgery on l/4,l/5. now have foot and calf pain. what is causing this?

Nerve root: Selective irritation of the nerve root at L4/L5. Google "dermatomes", and you can see the nerve distribution for the lumbar nerves. There is probably some post-surgical swelling and inflammation at the site of the surgery which is causing this. Hopefully, it will get better over time. Try Boswella (a powerful anti-inflammatory herb) and topical DMSO ("horse liniment") available in a feed store