Surgeons generally assess the mobility of the ossicle chain by manual palpation using rigid elongated hooks inserted through the ear canal. As the applied forces are in the range of a few grams equivalent force, the measurement remains subjective and its reliability highly dependent on the level of experience and skills of the surgeon. This paper presents the design, modelling and experimental testing of an innovative surgical device based on a novel compliant constant-force mechanism used to apply a predefined force of 1 gf (9.81 mN) to the ossicles. Using this handheld constant-force tool along with an operating microscope for visual feedback of ossicle displacement, surgeons can objectively quantify ossicular mobility.