WHILE VEHICLE WAS STOPPING, ANOTHER VEHICLE REAR-ENDED CONSUMER'S VEHICLE A T 40 MPH. DURING IMPACT, LOCKING MECHANSIM THAT HELD DRIVER'S SEATBACK IN AN UPRIGHT POSITION BROKE, CAUSING SEAT TO FALL BACK INTO REAR SEATING POSITION. DRIVER SUSTAINED HEAD/ NECK/ BACK, AND RIB INJURIES. PLEASE PROVIDE ANY ADDITIONAL INFORMATION/ATTACHMENTS.*AK