Is he mobile? If so, water therapy can be good. Very hot baths with jets. Like a jacuzzi. Pain meds are never the answer. maybe acupuncture? Its not usually covered by insurance, but also not very expensive. Also a hyperbaric chamber restores tissues in the body. That can be costly, but a lot of insurances cover some of it and a ton of physical therapy offices have them now.
First, sorry for your son. I have a very good friend who had a similar problem and acupuncture did a world of difference. His pain diminished drastically and now for almost 2 years after a 3 month treatment (weekly). Nothing to loose. Also chiropractic can help too.
It always helps to pray and ask god to heal his body unless you have a different religion. But it work for me and I know it will work for anyone God is all see all knowing and all mighty just try him he will never fail you and also consult a lawyer if the job or the doctor or insurance company refuses to continue to pay for the cost of treatment and medications etc.