Abstract: A device for measuring femur bone displacement during total hip arthroplasty includes a base element immovably mounted to the pelvis and a measurement arm, detachably mounted to the base element via a support, and the measurement arm is fitted with a microprocessor computing system with a display screen. The measurement arm includes at least two movable links, serially connected with each other and with support by rotary joints with at least one (and preferably three) degrees of freedom, whereby both movable links are fitted with an accelerometer (preferably a three-axis accelerometer) and/or a magnetic field sensor and/or a gyroscope, preferably forming together an integrated acceleration, magnetic field and gyroscopic sensor unit.