CAR "TOTALED" IN REAR-END WRECK. PASSENGER SEATBACK COLLAPSED WHEN HIT FROM REAR, HARD CONTACT WITH 3-POINT SEAT BELTS WHEN THROWN FORWARD WHEN CAR CRASHED INTO VEHICLE STOPPED IN FRONT. GOT RIDE TO HOSPITAL IN AMBULANCE! DRIVER SIDE SEAT BACK DID NOT COLLAPSE, DRIVER OKAY.