I've used chiropractic for my hounds (and myself) and feel it can be very beneficial. My bridge boy, Keno, started leaking urine out of the blue when I first adopted him. I'd read that sudden incontinence in males dogs could result from a lumbar vertebra being out of alignment. Since I'd just taken him to his first ever play group and he had run and played like a wild man, I took Keno in for an overall checkup and a chiropractic consult. The adjustment stopped the urine leakage right away. It happened once again about two years later, and immediately resolved after an adjustment.
I can't speak to whether or not Zip's particular problem would benefit, but if you can locate a chiropractor in your area, I think it would be beneficial to have him checked out.
Good luck. I hope he continues to improve.