Burning in the feet sounds like peripheral neuropathy. Certain medicines such as Lyrica, Cymbalta or Neurontin may be helpful for this.
His problem may relate to spinal cord or nerve root compression as one possibility. (I don't know what type of surgery that he has had) It is sometimes of value to rule out a secondary potential cause such as B-12 deficiency or diabetes as a couple of common examples of causes of peripheral neuropathy.
I hope this information helps. Further questions are welcome if you have others. If my answer has been helpful and to your satisfaction then please remember to press the "ACCEPT" button. Thank You and Best Regards,
Anthony Bray MD