how common is the use of ultran/tramadol for severe back pain

Ultram or tramadol is commonly used for back pain. General recommendations for Ultram are 1-2 50 mg. tablets every 4-6 hours for severe pain with no more than 8 pills a day.

Drugs.com suggestion that Ultram's effects can wane after 'a few weeks' in some people suggests that it should take effect fairly quickly but I was unable to get a good answer on that. There is generally a phase-in period if you're going to be taking higher doses of the drug so if you're in the beginning of that you won't be seeing all the effects of the drug.

http://www.spine-health.com/treatment/pain-medication/ultram-pain-reliever

Good luck!

Tramadol should help in 15 minutes to a half hour.  If you're thinking it needs time to build up, no.  It's a non-narcotic that works in two ways. One is as a mu opiod agonist, meaning it acts like an opoid, and secondly by working on the serotonin system.  That may be where the idea that it took time to work came from, because most drugs that get used for pain that work on the serotonin system are tricyclics that take 2-12 weeks to work.  If tramadol doesn't at least help a little in half an hour it's never going to.  Ask if something else might be more effective.