I'm not sure how amenable you are to alternatives, but after suffering myself with chronic pain in the past and discovering kratom to help with the pain in lieu of a narcotics prescription, I would suggest looking into this to improve your grandfather's quality of life. Years ago, my dad had surgery to "fix" a turn muscle that healed poorly, and was prescribed Tramadol for long-term pain management. After the docs started cutting everyone off, my dad suffered greatly from the pain, and I couldn't stand to see him like that, so I introduced him to kratom, as well. He takes it once in the evening before bed and he has also stopped getting regular migraines. The kratom subreddit is a good place to start looking for information. Just be aware that special interests have been spreading disinformation for a couple of years now, so take everything you read with a grain of salt. Do your own research and draw your own conclusions. There is a growing body of research available to help.