1. An apparatus comprising: one or more processing devices and one or more storage devices storing instructions that are operable, when executed by the one or more processing devices, to cause the one or more processing devices to perform operations comprising: receiving signals from a magnetic sensor located at a known position relative to an orthopaedic implant, the orthopaedic implant defining a hole that admits a transfixion element, the hole being defined to admit a transfixion element at two or more targeting locations in the hole; selecting a first targeting location of the two or more targeting locations; determining, based on the signals, a position of a landmark identifier relative to the first targeting location; and indicating the position of the landmark identifier relative to the first targeting location.