Non-contact actuation of less-invasive bone lengthening device using embedded cycloidal motor driven by permanent magnets from the outside

摘要

This paper proposes a miniaturized non-contact actuation mechanism for a surgical device for bone extension operation. This device is embedded inside the body, and the device controls the gap between the bones cut by the operation. A screw-nut mechanism was used for extension and the screw shaft was turned by a cyloidal reducer. A permanent magnet was attached to the ring gear of this cycloidal reducer, and the force applied to the ring gear magnet was Controlled by permanent magnets from outside of the device without direct mechanical contact. The outside magnets were attached at the ends of two bars, which were turned by two stepping motors. Combination of repulsive force and attractive force was selected in a sequence so as to realize the wobbling motion of the ring gear. The dimensions of the device were 7 mm in diameter and 39.7 mm in length. The output thrust was 2.1 N.