Burning pain is the cardinal sign of an unhappy nerve, probably the left L3+L4 nerve in your husband's case. Nerve pain is very difficult to treat as you have already discovered. Many special medications are used not necessarily "narcotics" which I assume you mean opioids medication like morphine and not other narcotics like Valium. What about other mediciations?
Tricyclic antidepressants should really be called tricyclic anagesics because they work so well for nerve pain. Desiprimine is often a favorite because it has the least amount of side effects.
Anti-convulants like gabapentin or Lyrica are also very, very useful for nerve pain.
A newer opioid is called Nucynta and it too works well for nerve pain.
I assume your husband is working with a pain specialist, but maybe a second opinion from another pain specialist would help provide a breakthrough for your difficult situation. Sometimes alternative solutions are found when looking from a different perspective.
Dr. Christina Lasich, MD