Ultrasonically assisted cutting blades for large bone surgeries

Abstract

Ultrasonic bone cutting is known to offer advantages over more conventional techniques, however ultrasonic surgical devices for hard tissues are currently limited to small bone procedures. This study investigates the potential benefits of an ultrasonically assisted sagittal saw, and explores two designs based on incorporating planar ultrasonic transducers in sagittal saw blades. Designs were developed using finite element analysis (FEA) and were subsequently characterised using experimental modal analysis (EMA). Both blades were tuned to operate in a longitudinal mode of vibration. The dynamic response characterisations were measured and compared, using a harmonic analysis involving bi-directional frequency sweeps through the tuned longitudinal resonance at increasing excitation levels. The blades were tested in a linear loading rig, where they were drawn across a fixed piece of bone substitute material, mimicking a typical cut of a sagittal saw. Each blade was tested first with no ultrasonic excitation, and then under ultrasonic excitation. The depth of cut and the current draw of the drive actuator was recorded for comparison of performance. The results of the tests show that the current draw remained constant for control and ultrasonically excited cuts, whilst one design demonstrated a greater depth of cut for an ultrasonically excited blade.