Development of a Vibration Exciter for Ultrasonic Controlled Growing Rod System at Minimally Invasive Surgery

One of the treatment for the scoliosis is the surgery for attaching a metal rod to spines. It is necessary to conduct the surgery again if the patient grows up. We have been developing the new mechanism rod that enables the length of the gap of the spina to be controlled using ultrasonic vibration. It is important to design the horn to transmit the ultrasonic vibration to the rod effectively. This paper describes the design guideline of the horn for adapting the developed controlling rod system. First, the requirement of the horn is arranged, and the guideline is shown. Next the vibration modes are considered if the shape of the horn is not satisfied for the design guideline. Using the consideration, we confirm the importance of the design guideline. Finally, the actual horn is developed along the proposed design guideline, the stable vibration is verified.