EMPLOYEE WAS HELPING TO LIFT A FIRE EXTINGUISHERTHAT WAS HANGING FROM WIRE MESH ON AN INSULATED HOOK. HE PLACED HIS LEFT HAND UNDER THE BOTTOM OF THE EXTINGUISHER WHEN HE FELT A POP AND A BUR NING FEELING IN HIS LEFT SHOULDER. EMPLOYEE HAD SURGERY ON 6/13/00 TO REPAIR A TORN ROTATOR CUFFAND BEGAN MISSING WORK.