Developing an Ultra-Sonic Screwdriver for Detecting the Overtightening of Orthopaedic Screws

BACKGROUND

Complications following fracture fixation surgery that require revision are very costly to the National Health Service (NHS) and can have a dramatic impact on a patients healing time, increasing the risk of infection. A major aspect of fixation failure is through the overtightening of the medical screws that hold a fixation plate in position. If a screw is overtightened, the thread of the screw strips away bone material, causing the screw to become loose and therefore causing screw-bone interface failure.

This in turn can result in failure of the fracture fixation, leading to revision. Currently screw tightening is based on the surgeons’ personal experience. Torque meters cannot be applied in this situation due to the large variation in bone densities. A possible method of preventing over-stripping is Acoustic Emission (AE) which is the detection of the stress waves released as a material undergoes stress.

PROJECT AIMS AND METHODS

Preliminary studies using AE during orthopaedic screw fixation have been performed using polyurethane foam as the bone-simulating material, demonstrating the applicability of the technique. Data showed that AE 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.

Feasibility of Completion is within 3.5 years.

All facilities are available for the completion of this project. In addition previous work at Cardiff University has demonstrated the fundamental science. Finally, there are two strong industrial partners (Microsemi and Zimmer Biomet) who will support and steer the project.

ELIGIBILITY

You should have obtained, or be about to obtain, a First or Upper Second Class UK Honours degree, or the equivalent qualifications gained outside the UK.

Applicants with a Lower Second Class degree will be considered if they also have a master’s degree. Applicants with a minimum Upper Second Class degree and significant relevant non-academic experience are encouraged to apply.