Application to Biomaterial of a Vibration Exciter for Ultrasonic Controlled Growing Rod System

Scoliosis is a symptom of the deformation of the backbone, and a few percentage of teenagers suffer from it. The patient needs to receive the operational surgery, if the curve of backbone is over the certain degrees. In the surgery, pedicle screws are planted in the backbone, and fixed by the straight rod. And the surgical operation is given many times until the patient stops growing up, since the backbone is extension according to growth of the patient. Therefore, a method that the surgical operation is not necessary is desirable. We have developed a growing rod that is able to be controlled using an ultrasonic vibration. In the previous work, the primitive principle of the growing rod was proposed, and were verified by some experiments in an ideal state. It is important to verify the proposed principle using the biomaterial to progress the nextstage (the crinical trials). In this paper, the proposed method is verified using biomaterial that is the meat with bone for food. And, the extension force that occurs in the backbone is discussed, since the length of the gap of the backbone becomes large according to growth of the patient. As a result, it is clear that the extend force of the rod is proportional to the magnitude of the extend force that occurs in spine. Therefore, the extension of the rod stop naturally, if the force in the backbone is released. We confirm that this method has safety.