I have a very good friend with a similar story about long term back problems. He was on oxycontin for literally 10 years along with other medications. Multiple back surgeries.

Then when his prescribing doctor got arrested, he ended up detoxing involuntarily at first, and then voluntarily, and he found that he didn't have any pain after he managed to make it through withdrawal.

I honestly think a lot of people with chronic pain that they're treating with opiates are actually treating withdrawal with opiates.