Direction-dependent analysis of force and torque in conventional and ultrasonically-assisted drilling of cortical bone

Bone drilling is a common surgical procedure in orthopaedic, neuro, and dental surgeries for internal fixation. Estimation and control of the bone drilling force and torque are critical in preventing drill breakthrough, excessive heat generation and unnecessary mechanical damage to the bone. This paper illustrates experimental measurements, and a comparison of the drilling thrust force and torque in Conventional Drilling (CD) and Ultrasonically-Assisted Drilling (UAD), in two directions; along the longitudinal axis of the bone and normal to it (radial direction). The objective of this research is to find the effect of drill size and ultrasonic vibration superimposed on drill movement, on the thrust force and torque. The effect of drill speed on force was investigated in the described directions, followed by a series of experiments, to explore the influence of drill size and penetration direction on the level of force and torque. The drilling force and torque were found to be strongly dependent on the drilling direction. Experimental results reveal that when drilling in a specific direction, lower drilling force and torque are found in UAD compared to CD.