Before concluding that the symptoms are due to nerve compression, it is important to know whether an MRI of the lumbar spine has been done and whether it shows significant nerve root compression corresponding to his symptoms. If there is MRI evidence of nerve compression, image-guided epidural or selective nerve root injections may provide meaningful pain relief and improve walking ability, even if surgery is not being considered. At 81 years of age with underlying heart disease, surgery may carry significant risks, and even positioning him prone during surgery can be challenging depending on his overall health. I would recommend reviewing his MRI and consulting a Neurosurgeon to see if pain interventions are suitable for him.

81 years of age with stents in the heart are not a medical absolute contraindication for surgery. If physiotherapy and other conservative methods have failed, surgery could be the only sensible option. Perhaps the surgery could be done under local anaesthesia + epidural anaesthesia - an experienced surgeon + anaesthetist can guide you. Medications for nerve pain relief can have side effects as well and may not be very effective.