I don't know about drug testing and Tramadol, but I do know that if you notify your employer that you are taking medication perscribed by a doctor and what that medication is.
I've been in the military and my husband has also. He has had to take narcotics after back surgery and "passed" his drug test during this time because his employer was informed and in his case, had his medical record.
Keep the lines of communication open. I hope you heal quickly.