A device for determining deformation of an intramedullary rod comprises a longitudinal probe sized and shaped to be inserted into a channel of the rod and including a deflection detection element, a head portion including a lumen extending therethrough and a coupling element to attach the head portion to a proximal end of the intramedullary rod, the lumen slidably receiving the probe therein, and a logging unit configured to detect relative movement between the probe and the head portion and to determine a current path of the intramedullary rod from the relative movement.
