MATEC Web Conf.
Volume 148, 2018International Conference on Engineering Vibration (ICoEV 2017)
|Number of page(s)||7|
|Section||Vibration-Based Structural Health Monitoring Data Analysis and Time Series Methods|
|Published online||02 February 2018|
Vibro-acoustic and nonlinear analysis of cadavric femoral bone impaction in cavity preparations
University of Technology Sydney, Centre for Audio, Acoustics and Vibration, Faculty of Engineering and Information Technology, Sydney, Australia
2 Hamburg University of Technology, Dynamics Group, Mechanical Engineering, Hamburg, Germany
3 Imperial College London, Department of Mechanical Engineering, London, United Kingdom
4 Hamburg University of Technology, Institute of Biomechanics, Mechanical Engineering, Hamburg, Germany
5 Hamburg University of Applied Sciences, Department of Life Sciences, Hamburg, Germany
6 University of New South Wales Canberra, School of Engineering and IT, Canberra, Australia
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Owing to an ageing population, the impact of unhealthy lifestyle, or simply congenital or gender specific issues (dysplasia), degenerative bone and joint disease (osteoarthritis) at the hip pose an increasing problem in many countries. Osteoarthritis is painful and causes mobility restrictions; amelioration is often only achieved by replacing the complete hip joint in a total hip arthroplasty (THA). Despite significant orthopaedic progress related to THA, the success of the surgical process relies heavily on the judgement, experience, skills and techniques used of the surgeon. One common way of implanting the stem into the femur is press fitting uncemented stem designs into a prepared cavity. By using a range of compaction broaches, which are impacted into the femur, the cavity for the implant is formed. However, the surgeon decides whether to change the size of the broach, how hard and fast it is impacted or when to stop the excavation process, merely based on acoustic, haptic or visual cues which are subjective. It is known that non-ideal cavity preparations increase the risk of peri-prosthetic fractures especially in elderly people.
This study reports on a simulated hip replacement surgery on a cadaver and the analysis of impaction forces and the microphone signals during compaction. The recorded transient signals of impaction forces and acoustic pressures (≈ 80 μs - 2 ms) are statistically analysed for their trend, which shows increasing heteroscedasticity in the force-pressure relationship between broach sizes.
Tikhonov regularisation, as inverse deconvolution technique, is applied to calculate the acoustic transfer functions from the acoustic responses and their mechanical impacts. The extracted spectra highlight that system characteristics altered during the cavity preparation process: in the high-frequency range the number of resonances increased with impacts and broach size. By applying nonlinear time series analysis the system dynamics increase in complexity and demand for a larger minimum embedding dimension. The growing number of resonances with similar level of the transfer function indicates a higher propensity to dissipate energy over sound; the change in embedding dimension indicates a decrease in linearity. The spectral changes as well as the altered dimension requirements indicate either an improved coupling between the bone and the broach or the onset of micro-fractures caused by growing stress levels within the bone.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).
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