TIRE TREAD SEPARATED CAUSING THE VEHICLE TO SKID THEN SPIN THEN ROLL 4 TIMES. DRIVER SUFFERED A HEAD INJURY REQUIRING HOSPITAL CARE. FRONT PASSENGER WAS NOT INJURED. BACK SEAT PASSENGER WAS EJECTED FROM THE VEHICLE AND SUFFERED A FRACTURED L2 VERTEBRAE. (DOT NUMBER: UNKNOWN TIRESIZE: P235/75R15)