A method for estimating at least one of a fastener-hole depth and a fastener length prior to forming a hole in a bone can include selecting a position on a proximal side of a proximal cortical bone layer for forming the hole, transmitting a transmitted wave into the bone from the selected position, and receiving a reflected wave at the selected position after the transmitted wave has been reflected by a distal cortical bone layer. The method can further include determining a distance from the selected position to the distal cortical bone layer based on times at which the transmitted wave is transmitted and the reflected wave is received, and estimating the at least one of the fastener-hole depth and the fastener length based on the distance to the distal cortical bone layer.
