Seriously? Where?
http://en.wikipedia.org/wiki/Chiropractic_education
Chiropractic--Doctor of Chiropractic (D.C. or B.Chiro or M.Chiro), a curriculum divided into "straight" or "progressive" chiropractic depending upon the philosophy of the institution, generally requiring 4 academic years of full-time study after 2-4 years or more of study at the associate or bachelor's degree level.
while not a phd (neither is a medical degree though) it seems to allow them the title Dr.