Described is a reference pin for use during a bone fracture treatment. The pin may include a longitudinal shaft and a spreading member. The longitudinal shaft with a longitudinal axis, a front end, a rear end and a through hole penetrating the shaft from the front end to the rear end. The shaft includes a rear portion adjoining the rear end and an expandable front portion adjoining the front end. The expandable front portion is insertable in a distal locking hole of an intramedullary nail and reversibly expandable transversely to the longitudinal axis. The spreading member is moveably located in the through hole and apt for reversibly expanding the expandable front end portion. The expandable front portion is reversibly expandable within a range between 0.3 mm and 0.5 mm.