Multigrain Smoothed Particle Hydrodynamics and Hertzian Contact Modeling of the Grinding Force in Atherectomy

Abstract

This study investigated the grinding force in rotational atherectomy, a clinical procedure that uses a high-speed grinding wheel to remove hardened, calcified plaque inside the human arteries. The grinding force, wheel motion, and ground surface were measured based on a ring-shape bovine bone surrogate for the calcified plaque. At 135,000, 155,000, and 175,000 rpm wheel rotational speed, the grinding forces were 1.84, 1.92, and 2.22 N and the wheel orbital speeds were 6060, 6840, and 7800 rpm, respectively. The grinding wheel was observed to bounce on the wall of the bone surrogate, leaving discrete grinding marks. Based on this observation, we modeled the grinding force in two components: impact and cutting forces. The impact force between the grinding wheel and the bone surrogate was calculated by the Hertz contact model. A multigrain smoothed particle hydrodynamics (SPH) model was established to simulate the cutting force. The grinding wheel model was built according to the wheel surface topography scanned by a laser confocal microscope. The workpiece was modeled by kinematic-geometrical cutting. The simulation predicted a cutting force of 41, 51, and 99 mN at the three investigated wheel rotational speeds. The resultant grinding forces, combining the impact and cutting forces modeled by the Hertz contact and SPH simulation, matched with the experimental measurements with relative errors less than 10%.