Feasibility of detecting orthopedic screw overtightening using Acoustic Emission

A preliminary study of Acoustic Emission during orthopaedic screw fixation was performed using polyurethane foam as the bone-simulating material. Three sets of screws, a Dynamic Hip Screw, a small fragment screw and a large fragment screw were investigated, monitoring acoustic emission activity during the screw tightening. Some specimens were overtightened on purpose to investigate the possibility of identifying the stripping torque before stripping actually occurred. One set of data was supported by load cell measurements to directly measure the axial load through the screw. Data showed that Acoustic Emission can give good indications of impending screw stripping; such indications are not available to the surgeon at the current state of the art using traditional torque measuring devices, and current practice relies on the surgeon’s experience alone. The results suggest that Acoustic Emission may have the potential to prevent screw overtightening and bone tissue damage, eliminating one of the commonest sources of human error in such scenarios.