The method for preventing extravasation of bone cement used in balloon kyphoplasty involves first forming a void in a vertebral body. A pair of unfilled balloons are then inserted into the void in the vertebral body. An injection tube or catheter is inserted through an inlet port of each of the balloons, and the balloons are filled with bone cement. The injection tubes are then removed from the inlet ports. The bone cement is preferably provided in the form of pellets or granules. The inlet ports are each provided with a seal, such as an elastic band mounted thereabout, or the like, allowing the inlet port to be automatically sealed as soon as the corresponding injection tube is withdrawn. The device includes at least the balloon and the seal, but may be furnished as a kit that also includes the bone cement and injection tube.
