EE was operating scraper, reclamating, and hit hard frozen chunk of dirt which jarred lower back. EE saw MD on 3-13-09 who instructed him to see a Chiro (thus constituting MSHA Reportability). EE sought Chiro treatment on 3-16-09, return to Duty 3-17-09, no restrictions, no Lost days (Fri/Mon off for medical attention/appointments available).