Embodiments of the bone anchor assembly (36, 50) described herein have adjustable lengths and therefore accommodate many needs. Therefore, the physician does not need to maintain a multitude of bone anchors having a variety of lengths in order to be prepared for many situations. The bone anchor assembly (36, 50) has an elongated hollow shaft portion (38, 52) formed of multiple shaft segments (46, 58) joined together. The length of the shaft portion (38, 52) is adjusted after the implanting of the bone anchor assembly into the bone by removing shaft segments (46, 58).
