Before making any decisions about epidural (Depr-Medra) injections in the low back, you may want to read information on this website: http://www.burtonreport.com/infspine/AdhesArachEpiInjKoontz.htm
I have had multiple low back surgeries and now suggesting injections. I have rejected this offer due to the problems that can arise. Read the information for yourself before making a decision. Good Luck
Theoretically, if you block the L4 or L5 nerve at the root, then it should provide analgesia for all areas innervated by those nerves. However, in reality, it's possible the nerve block is only partial or if the problem is a neuroma or mass in the foot affecting distal nerves, then the medication may not be helpful. Good luck.