Chiropractic theory and practice has long since been justified in the larger world of patient satisfaction. And it has been justified to many insurance companies because 1) it does the job, and 2) it costs far less than comparable medical treatment for the same condition. Many State Industrial Insurance agencies have found that it returns people to the job far faster and with less cost than comparable medical treatment (i.e., half a dozen chiropractic adjustments and a few days rest as opposed to putting someone's spine in traction for a couple of weeks, or putting them in a back-brace and feeding them pain-killers for the rest of their lives). If you insist, I can provide a deluge of statistics on this, provided by insurance companies and state government agencies.
I know of no independent, unbiased scientific investigation that has ever been done on chiropractic. There have been a number of "scientific investigations" by members of the medical profession, all of which conclude that chiropractic is ineffective at best and quackery at worst.
One such "investigation" established that it is impossible to adjust a spine. The method? The researchers placed a 500 lb. weight on a vertebra of a cadaver's spine and it wouldn't move. Ergo, chiropractic is pure hokum. A properly give chiropractic adjustment relies on the reflex action of living muscles. Of course it wouldn't work on a cadaver. Any more than poking pills down the throat of a cadaver will cure it of much of anything. Besides, there are millions of people walking around (usually a little straighter than they did when they first walked into a chiropractor's office) who are living proof that chiropractic works.
No. I would like very much to see a good, unbiased scientific investigation of chiropractic. But so far, there has never been one performed by any agency that didn't have it's own ax to grind.
That's rather like expecting MacDonald's to endorse Burger King.