Employee was operating Loci when he jolted his back in the seat as the loci & train transitioned from rail to pocket rollers. He RTW & continued assigned duties, no day missed. No new event, inj. or work cond. aggravated injury. Became DAFW when doctor took him off work due to employee complaints of cont. pain. Appt to consult for surgery - June, 2010. First day missed 5-12-10.