I too sympathise. I have back problems and my back has gone into spasm twice, once when I just reached out to pick up the phone. Latest time we called out paramedics as the pain was so bad. Apart from (strong) painkillers and anti-imflammatories A & E could do nothing.
The problem can move, I understand, because by trying to relieve the pain in his back your hubby will be putting strain on other muscles, which eventually start to complain themselves.
I now see a chiropractor on a regular basis, as hopefully prevention is better than cure. I run my own business which is 7 days a week, so I can't afford to be out of action. My chiropractor will just lightly run his hands down my back and tell me certain muscles are tense and tight. When he starts to work on these muscles I can tell he was right!
It's almost like magic.
On the subject of chiropractic/osteopathy, I have discovered a chiropractor who practises the McTimoney Method.
This uses small movements and taps to "jog" the muscles and bones back into place. Unlike conventional osteopathy, there is none of this heaving and cracking of bones and joints. Much better, believe me.
Look up McTimoney on the web, see what you think and see if there's a practitioner near you.