An ultrasonically assisted sagittal saw for large bone surgeries

Large bone cutting surgeries are predominantly undertaken using sagittal saws, whereas ultrasonic devices are currently limited to small shallow cuts in bone, for example in maxillofacial surgeries. Given the known benefits of ultrasonic cutting, this study considers an approach of superimposing ultrasonic vibration on a sagittal saw blade motion by designing the saw as a planar transducer. Finite element modeling was used to establish piezoceramic and blade geometries, culminating in two designs, one for a longitudinal-mode transducer and one for a lateral-mode transducer. The two resulting planar transducers were manufactured, with the piezoceramic plates bonded to the blades using a high strength epoxy. Impendence plots confirmed the tuned ultrasonic frequency for each transducer. The ultrasonic vibration amplitude of the blade was also measured, although was limited by the device tracking and drive system. Initial cutting tests carried out on a sagittal saw test rig demonstrated small reductions in cut temperature and cut time compared with control blades. These are very early, but promising results for developing this new surgical technology.