Low-damage bone cutting using a newly developed rotary ultrasonic surgical handpiece

Abstract

Bone cutting is a common procedure in surgery, during which conventional rotary cutting causes extensive damage to the bone while single ultrasonic cutting, as a newer tool, results in minimally invasive injury but has obviously low efficiency. This study aimed to achieve low-damage, high-efficiency bone cutting using a newly developed surgical rotary ultrasonic (RU) handpiece coupled with ultrasonic vibration and rotary cutting. To solve the clinical miniature size and power limits, a quarter-wave barbell ultrasonic horn with a mid-reduction structure was designed based on the vibration theory. It enhanced the vibration amplitude output by 22% compared with a common stepped horn. A new non-contact rotary transformer with “T+U” shaped cores was developed with a higher coupling coefficient of 0.95 and transmission efficiency of 94% compared with common industrial transformers. Handpiece performance was evaluated in terms of vibration responses and cutting characteristics during cortical bone cutting. The results demonstrated that the new tool had good vibration characteristics with the expected amplitude and frequency, even at a low power of approximately 1 W, which was less than 1/100 of that used in industrial RU tools. Compared with conventional rotary cutting, the new tool significantly reduced cutting forces by 32%–44% without losing cutting efficiency and diminished surface chipping damage in the bone, which was especially important for low-trauma surgery. This study advances the bone cutting processes for high-quality surgery by developing a new RU surgical tool.